ESTRO 2023 - Abstract Book

FromInovation toAction

12-16May2023 Vienna,Austria

Radiotherapy &Oncology Journal of the European SocieTy for Radiotherapy and Oncology

Volume 182 Supplement 1 (2023)

Radiotherapy & Oncology is available online: For ESTRO members: http://www.thegreenjournal.com For institutional libraries: http://www.sciencedirect.com

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12-16 May 2023 Vienna, Austria

Table of contents

SATURDAY 13 MAY 2023

Teaching lecture Health services research for trialists...................................................................................................................... (abs. 0001) Radiation-induced tumour cell migration - Why does it matter and what can we do about it?....................... (abs. 0002) Total neoadjuvant therapy in rectal cancer: When, why, how............................................................................. (abs. 0003) Role of PET/CT for treatment planning optimisation in salvage prostate radiotherapy................................... (abs. 0004) Survey results and systematic review of the dosimetry information in papers on SBRT clinical trials.... (abs. 0005-0006) What’s new in deep-learning?. ................................................................................................................................ (abs. 0007) Patient comfort during radiotherapy. .................................................................................................................... (abs. 0008) The role of brachytherapy in the treatment of primary and recurrent vulvar cancer. ........................... (abs. 0009-0010) Joint Symposium ESTRO-ASTRO: Personalised radiotherapy in 2023 - What can we implement now?.............................. (abs. 0011-0014) Symposium Lipids and metabolomics in radiation response - An emerging paradigm in radioresistant cancers?.... (abs. 0015-0018) Debate This house believes that non-metastatic pancreatic cancers should be treated with SBRT................... (abs. 0019-0024) Symposium Targeting acute and late toxicity in head & neck radiotherapy................................................................. (abs. 0025-0028) Joint Symposium ESTRO-EFOMP: International/European initiatives in medical physics..................................................... (abs. 0029-0032) Symposium Full speed towards automatic radiotherapy - How to commission and implement these new tools... (abs. 0033-0037) Immobilisation and verification. ................................................................................................................... (abs. 0038-0040) Debate This house believes that centralisation will have a positive influence on the administration of brachytherapy procedures. ............................................................................................ (abs. 0041-0046) Mini-Oral Gynaecology.................................................................................................................................................... (abs. 0047-0054) TCP/NTCP modelling and prediction............................................................................................................ (abs. 0055-0062) Poster Discussion Palliative radiotherapy & SBRT...................................................................................................................... (abs. 0063-0074) Health services research; Education and training....................................................................................... (abs. 0075-0086) Proffered Papers Biomarkers and prediction models.............................................................................................................. (abs. 0087-0092) Microenvironment.......................................................................................................................................... (abs. 0093-0098) Upper GI.......................................................................................................................................................... (abs. 0099-0104) Head & neck.................................................................................................................................................... (abs. 0105-0110) QA and auditing.............................................................................................................................................. (abs. 0111-0116)

Autosegmentation & automation for QA..................................................................................................... (abs. 0117-0122) Tumour-specific innovations......................................................................................................................... (abs. 0123-0128) Gynaecology.................................................................................................................................................... (abs. 0129-0134) Mini-Oral Breast............................................................................................................................................................... (abs. 0135-0142) Trends in dosimetry planning....................................................................................................................... (abs. 0143-0150) Poster Discussion Lung 1.............................................................................................................................................................. (abs. 0151-0162) Radiomics and modelling. ............................................................................................................................. (abs. 0163-0174) Symposium Presidential symposium - From innovation to action: The 2nd translational gap................................... (abs. 0175-0178) Award Lecture E van der Schueren Award. ........................................................................................................................... (abs. 0179-0180) Jens Overgaard Legacy Award....................................................................................................................... (abs. 0181-0182) Symposium Dose escalation............................................................................................................................................... (abs. 0183-0186) Radiotherapy-immunotherapy combinations - How does the tumour microenvironment keep tumours cold?........................................................................................................................................ (abs. 0187-0190) Joint Symposium ESTRO-CARO: Next generation radiation oncology - How to best obtain evidence for emerging technologies. ........................................................................................................................... (abs. 0191-0194) Symposium Controversies in postoperative radiotherapy of oral cavity cancer.......................................................... (abs. 0195-0197) Pitch Session Will automation of radiotherapy tasks solve more problems than it causes?......................................... (abs. 0198-0203) Symposium Clinical audits in radiation oncology: Current status and guidance for its implementation. ................. (abs. 0204-0206) Preparing for, and handling of, automated brachytherapy treatment planning in clinical practice. .... (abs. 0207-0210) Patient preparation and positioning. ........................................................................................................... (abs. 0211-0213) Mini-Oral Prostate........................................................................................................................................................... (abs. 0214-0221) Image processing and treatment evaluation............................................................................................... (abs. 0222-0229) Poster Discussion Breast............................................................................................................................................................... (abs. 0230-0241) Current challenges in proton therapy.......................................................................................................... (abs. 0242-0253) Proffered Papers Education and training / Professional development. ................................................................................. (abs. 0254-0259) Immuno-radiobiology. ................................................................................................................................... (abs. 0260-0265) Palliation - Oligometastases.......................................................................................................................... (abs. 0266-0271) Lower GI. ......................................................................................................................................................... (abs. 0272-0277) MR-Linac.......................................................................................................................................................... (abs. 0278-0283) Proton treatment planning............................................................................................................................ (abs. 0284-0289) Physics............................................................................................................................................................. (abs. 0290-0295) Mini-Oral Gynaecology, urology & physics. .................................................................................................................. (abs. 0296-0303) Audits and multi-centre studies.................................................................................................................... (abs. 0304-0311) Poster Discussion Technical improvements in radiotherapy practice. .................................................................................... (abs. 0312-0323) Automation and machine learning............................................................................................................... (abs. 0324-0335)

SUNDAY 14 MAY 2023

Teaching Lecture Bridging the gap between bulky tumours and radiotherapy: Spatially-fractionated radiotherapy....... (abs. 0336-0337) Radiation-induced cell death: A focus on ferroptosis........................................................................................... (abs. 0338) Outcome measures for trials in radiation oncology............................................................................................. (abs. 0339) Challenging scenarios with oligometastatic SABRs - Where do we go now?...................................................... (abs. 0340) A leap into clinical practice: Accurate treatment planning in presence of metallic implants................. (abs. 0341-0342) Effective expression of uncertainties - The hows, whys and don’ts.................................................................... (abs. 0343) The role of functional imaging in brachytherapy.................................................................................................. (abs. 0344) Global advancements in radiation therapist advanced practice......................................................................... (abs. 0345) Joint Symposium ESTRO-EORTC: Next generation clinical trial design: A multidisciplinary effort....................................... (abs. 0346-0349) Symposium Senescence in cancer and stromal cells: Opportunities to improve radiotherapy response................. (abs. 0350-0353) How to optimise radiotherapy and immunotherapy combination........................................................... (abs. 0354-0357) Joint Symposium ESTRO-EANO: Changing the landscape for multidisciplinary treatment of brain metastases. .............. (abs. 0358-0361) ESTRO-ESR: Quantification of functional MRI parameters: New opportunities in radiotherapy?.......... (abs. 0362-0365) ESTRO-AAPM: Big data, big headache.......................................................................................................... (abs. 0366-0371) Symposium Risk-adapted personalised brachytherapy.................................................................................................. (abs. 0372-0374) Panel Discussion Evolutions in radiation therapist professional development..................................................................... (abs. 0375-0378) Mini-Oral Paediatrics - AYA............................................................................................................................................. (abs. 0379-0386) Modifications in IGRT..................................................................................................................................... (abs. 0387-0394) Poster Discussion Head & neck.................................................................................................................................................... (abs. 0395-0406) Clinical Brachytherapy. .................................................................................................................................. (abs. 0407-0418) Proffered Papers Translational outputs from clinical trials. .................................................................................................... (abs. 0419-0424) Tumour radiobiology. .................................................................................................................................... (abs. 0425-0430) Genito-urinary................................................................................................................................................. (abs. 0431-0436) Haematology - CNS. ....................................................................................................................................... (abs. 0437-0442) CT reconstruction and synthetic CTs............................................................................................................ (abs. 0443-0448) Toxicity modelling........................................................................................................................................... (abs. 0449-0454) Breast, GI and paediatrics. ............................................................................................................................ (abs. 0455-0460) Advancements in RTT practice...................................................................................................................... (abs. 0461-0466) Mini-Oral Lung................................................................................................................................................................. (abs. 0467-0474) Advanced treatment planning with photons and particles........................................................................ (abs. 0475-0482) Poster Discussion Patient management strategies.................................................................................................................... (abs. 0483-0494) Physics brachytherapy................................................................................................................................... (abs. 0495-0506) Proffered Papers Highlights of Proffered Papers - Best papers.............................................................................................. (abs. 0507-0512) Award Lecture C Regaud Award. ............................................................................................................................................ (abs. 0513-0514) Iridium 192 Award.......................................................................................................................................... (abs. 0515-0516) Joint Symposium ESTRO-ESC: New cardio-oncology guidelines: Current state of knowledge and future directions........ (abs. 0517-0520)

Symposium Individualising radiotherapy dose according to normal tissue effects - Are we there yet?.................... (abs. 0521-0523) Do radiotherapy techniques impact the concept and size of planning target volumes margins?......... (abs. 0524-0526) Joint Symposium ESTRO-IASLC: New treatment strategies for stage III NSCLC and innovative biomarkers for patient’s selection and monitoring. ..................................................................................................................................................... (abs. 0527-0530) Debate This house believes that C-arm linac is no longer the work-horse of radiotherapy................................ (abs. 0531-0536) Symposium AI for (online?) IGRT........................................................................................................................................ (abs. 0537-0541) Supportive care and toxicity assessment in brachytherapy. ..................................................................... (abs. 0542-0545) The role of radiation therapists in translating science to clinical practice. .............................................. (abs. 0546-0548) Mini-Oral CNS................................................................................................................................................................... (abs. 0549-0556) Patient and public perspective...................................................................................................................... (abs. 0557-0564) Poster Discussion Urology............................................................................................................................................................ (abs. 0565-0576) QA and auditing.............................................................................................................................................. (abs. 0577-0588) Proffered Papers Patient perspectives....................................................................................................................................... (abs. 0589-0594) Normal tissue radiobiology........................................................................................................................... (abs. 0595-0600) Gynaecology.................................................................................................................................................... (abs. 0601-0606) Lung................................................................................................................................................................. (abs. 0607-0612) Dose accumulation and dose prediction. .................................................................................................... (abs. 0613-0618) Photon treatment planning........................................................................................................................... (abs. 0619-0624) Urology............................................................................................................................................................ (abs. 0625-0630) Head and neck & physics............................................................................................................................... (abs. 0631-0636) Mini-Oral Radiotherapy and the heart.......................................................................................................................... (abs. 0637-0644) Poster Discussion CNS................................................................................................................................................................... (abs. 0645-0656) Imaging............................................................................................................................................................ (abs. 0657-0668) Mini-Oral Detectors & dose management.................................................................................................................... (abs. 0669-0676)

MONDAY 15 MAY 2023

Teaching Lecture FAIR data management in radiation biology and radiation oncology research................................................. (abs. 0677) Future-proofing radiotherapy access: The fine balance between preferences and sustainability.................. (abs. 0678) Modern radiotherapy techniques in skin cancer. ................................................................................................. (abs. 0679) Integration of radiotherapy into new therapeutic algorithms for lymphomas.................................................. (abs. 0680) Justification and dose optimisation in IGRT practices. ......................................................................................... (abs. 0681) Voxel-based modelling for NTCP predictions: State-of-the-art methodology and beyond. ............................. (abs. 0682) Combining immunotherapy with radiotherapy..................................................................................................... (abs. 0683) Symposium Adaptive radiotherapy: What do we know in 2023?. .................................................................................. (abs. 0684-0687) Our resources are limited! An insight on optimising radiotherapy resources for the future................. (abs. 0688-0691) Debate This house believes that internal mammary node irradiation of high-risk breast cancer should be the standard of care today.......................................................................................................... (abs. 0692-0697) Symposium Balancing the safety profile of SBRT............................................................................................................. (abs. 0698-0701) Smaller and faster: Updates in dosimetry and detectors. ......................................................................... (abs. 0702-0704) The physics of late effects. ............................................................................................................................ (abs. 0705-0708) Optimising IGRT and motion management strategies. .............................................................................. (abs. 0709-0711) Mini-Oral Head & neck.................................................................................................................................................... (abs. 0712-0719) Radiobiology. .................................................................................................................................................. (abs. 0720-0727) Poster Discussion Education is the RTT superpower................................................................................................................. (abs. 0728-0739) Inter-intra fraction.......................................................................................................................................... (abs. 0740-0751) Proffered Papers Health Services Research............................................................................................................................... (abs. 0752-0757) Late-breaking Papers..................................................................................................................................... (abs. 0758-0763) Breast............................................................................................................................................................... (abs. 0764-0769) Detectors and dose verififcation................................................................................................................... (abs. 0770-0775) Novel applications of MR imaging. ............................................................................................................... (abs. 0776-0781) Impact on daily treatment planning............................................................................................................. (abs. 0782-0787) Speed Dating Speed dating............................................................................................................................................................. (abs. 0788) Mini-Oral Improving the patient experience. ............................................................................................................... (abs. 0789-0796) Automation. .................................................................................................................................................... (abs. 0797-0804) Poster Discussion Pelvic cancers.................................................................................................................................................. (abs. 0805-0815) Radiobiology. .................................................................................................................................................. (abs. 0816-0827) Proffered Papers Highlights of Proffered Papers - Latest clinical trials.................................................................................. (abs. 0828-0833) Symposium & Networking Optimal health for all together - Looking ahead, what do staff and patients need to achieve this?..... (abs. 0834-0836) Award Lecture Interdisciplinary Award.................................................................................................................................. (abs. 0837-0838) Donal Hollywood Award. ......................................................................................................................................... (abs. 0839) Symposium Re-irradiation - A curative treatment option: Indications and results. ..................................................... (abs. 0840-0843) The possibility to improve patient care is endless. (Some) initiatives to integrate into radiotherapy departments of the future.............................................................................................. (abs. 0844-0847)

Joint Symposium ESTRO-JASTRO: Biology-adjusted radiation therapy................................................................................... (abs. 0848-0851) Symposium Breast cancer radiotherapy: Frequently asked questions from ESTRO’s multidisciplinary course........ (abs. 0852-0855) Biologically-guided radiotherapy - Where are we now more than 20 years since the introduction of biological target volumes?............................................................................................ (abs. 0856-0858) What can EBRT learn from brachytherapy and vice versa?........................................................................ (abs. 0859-0862) Debate This house believes that there is no role for the plan libraries approach in the era of real-time adaptive radiotherapy.................................................................................................................................... (abs. 0863-0868) Mini-Oral Biomarkers...................................................................................................................................................... (abs. 0869-0876) Adaptive radiotherapy. .................................................................................................................................. (abs. 0877-0884) Poster Discussion GI...................................................................................................................................................................... (abs. 0885-0896) New technologies for treatment planning and dose verification.............................................................. (abs. 0897-0908) Proffered Papers Challenges in global radiation oncology. ..................................................................................................... (abs. 0909-0914) Reirradiation. .................................................................................................................................................. (abs. 0915-0920) Prostate SBRT. ................................................................................................................................................ (abs. 0921-0926) Flash and proton measurement. .................................................................................................................. (abs. 0927-0932) Motion management. .................................................................................................................................... (abs. 0933-0938) Multidisciplinary advancement in stereotactic arrythmia radiotherapy................................................... (abs. 0939-0944) Mini-Oral Sarcoma - Haematology................................................................................................................................. (abs. 0945-0952) Novel imaging strategies. .............................................................................................................................. (abs. 0953-0960) Poster Discussion Lung 2.............................................................................................................................................................. (abs. 0961-0972) Treatment planning: Photons. ...................................................................................................................... (abs. 0973-0984)

TUESDAY 16 MAY 2023

Teaching Lecture Statistical methods and analysis for large datasets.............................................................................................. (abs. 0985) Paediatric radiotherapy - What is state-of-the-art?..................................................................................... (abs. 0986-0987) Optimal treatment of bladder cancer in the elderly and frail populations........................................................ (abs. 0988) Secondary malignancies from radiation - Is the prophecy fulfilled?................................................................... (abs. 0989) Status and recent developments in PET for adaptive radiotherapy. .................................................................. (abs. 0990) MRI-only radiotherapy: Principles, challenges and future prospects. ................................................................ (abs. 0991) Living with, and beyond, cancer.............................................................................................................................. (abs. 0992) Symposium Guidelines. ...................................................................................................................................................... (abs. 0993-1000) Back to the future - The automated radiation oncology workflow in 2030.............................................. (abs. 1001-1004) Debate Radiotherapy and oligometastatic prostate cancer - This house believes we are ready for a new treatment paradigm............................................................................................................................ (abs. 1005-1010) of gynaecological cancers.............................................................................................................................. (abs. 1011-1013) Reducing the target volumes in external beam therapy............................................................................ (abs. 1014-1016) Proton arc therapy: Status and potential..................................................................................................... (abs. 1017-1020) Advances in communication technologies within radiotherapy................................................................ (abs. 1021-1023) Debate This house believes that tumour-specific radiosensitisation is an unachievable radiobiological fantasy................................................................................................................................... (abs. 1024-1029) Symposium Shared decision-making in radiotherapy..................................................................................................... (abs. 1030-1032) to the metastatic setting................................................................................................................................ (abs. 1033-1035) ESTRO-ESGO-ESP: Guidelines on cervical cancer........................................................................................ (abs. 1036-1041) Symposium What’s new in particle therapy?.................................................................................................................... (abs. 1042-1045) Handling longitudinal imaging data. ............................................................................................................ (abs. 1046-1049) Use of virtual reality in radiotherapy............................................................................................................ (abs. 1050-1052) Symposium How to introduce innovations in risk stratification to clinical management Joint Symposium ESTRO-RANZCR: Role of radiotherapy in renal cell carcinoma: From the primary

DIGITAL POSTERS Interdisciplinary

Other................................................................................................................................................................ (abs. 1061-1087) Health economics / health services research.............................................................................................. (abs. 1088-1099) Education in radiation oncology. .................................................................................................................. (abs. 1100-1107) Clinical CNS................................................................................................................................................................... (abs. 1108-1161) Haematology................................................................................................................................................... (abs. 1162-1171) Head and neck................................................................................................................................................ (abs. 1172-1243) Breast............................................................................................................................................................... (abs. 1244-1301) Lung................................................................................................................................................................. (abs. 1302-1341) Upper GI.......................................................................................................................................................... (abs. 1342-1391) Lower GI. ......................................................................................................................................................... (abs. 1392-1408) Gynaecological................................................................................................................................................ (abs. 1409-1436) Biomarkers...................................................................................................................................................... (abs. 1437-1451) Urology............................................................................................................................................................ (abs. 1452-1547) Sarcoma/Skin cancer/malignant melanoma................................................................................................ (abs. 1548-1566) Paediatric tumours......................................................................................................................................... (abs. 1567-1570) Mixed sites/palliation..................................................................................................................................... (abs. 1571-1613) Physics Automation. .................................................................................................................................................... (abs. 1614-1666) Imaging acquisition and processing............................................................................................................. (abs. 1667-1698) Quality assurance and auditing. ................................................................................................................... (abs. 1699-1738) Detectors, dose measurement and phantoms. .......................................................................................... (abs. 1739-1796) Dose calculation. ............................................................................................................................................ (abs. 1797-1832) New technologies........................................................................................................................................... (abs. 1833-1856) Intra-fraction motion management and real-time adaptive radiotherapy............................................... (abs. 1857-1907) Inter-fraction motion management and offline adaptive radiotherapy................................................... (abs. 1908-1942) Optimisation, algorithms and applications for ion beam treatment planning. ....................................... (abs. 1943-1991) Optimisation, algorithms and applications for photon and electron treatment planning..................... (abs. 1992-2068) Physical aspects of quantitative functional and biological imaging.......................................................... (abs. 2069-2082) Radiomics, modelling and statistical methods............................................................................................ (abs. 2083-2127) Brachytherapy Brachytherapy: Breast. ............................................................................................................................................ (abs. 2128) Brachytherapy: Gynaecology......................................................................................................................... (abs. 2129-2162) Brachytherapy: Physics.................................................................................................................................. (abs. 2163-2183) Brachytherapy: Head and neck, skin, eye.................................................................................................... (abs. 2184-2191) Brachytherapy: Urology (prostate, bladder, penile).................................................................................... (abs. 2192-2199) Radiobiology Normal tissue radiobiology........................................................................................................................... (abs. 2200-2207) Microenvironment.......................................................................................................................................... (abs. 2208-2216) Tumour radiobiology. .................................................................................................................................... (abs. 2217-2235) Immuno-radiobiology. ................................................................................................................................... (abs. 2236-2245) RTT Patient care, preparation, immobilisation and IGRT verification protocols. ............................................ (abs. 2246-2286) RTT education, training, advanced practice and role developments........................................................ (abs. 2287-2303) RTT service evaluation, quality assurance and risk management............................................................. (abs. 2304-2320) RTT treatment planning, OAR and target definitions.................................................................................. (abs. 2321-2359)

ABSTRACTS

ESTRO 2023

Saturday 13 May

S1

Teaching Lecture: Health services research for trialists

SP-0001 Health services research for trialists K. Spencer United Kingdom

Abstract not available

Teaching Lecture: Radiation-induced tumour cell migration - Why does it matter and what can we do about it?

SP-0002 Radiation-induced tumour cell migration - Why does it matter and what can we do about it? J. Birch 1 1 University of Glasgow, School of Cancer Sciences, Glasgow, United Kingdom Abstract Text Radiotherapy (RT) is a highly effective and potentially curative treatment used in many solid cancers for local control and for palliative purposes. However, a body of research has emerged over the last few decades, across numerous cancer types that point to the potential for RT to promote metastatic spread. Numerous mechanisms have been implicated in this response including selective pressure on surviving cancer cells, increase of circulating tumour cells (CTCs), modulation of inflammatory and stress signalling, epithelial to mesenchymal transition, induction of actin-myosin contractility and promotion of an invasion-permissive tumour stroma. Despite the growing array of preclinical evidence, meaningful interrogation of the impact of RT on metastasis in the clinic is sparse, and the subject remains a contentious issue. The lack of clinical data to support RT induced metastasis potentially invokes a false sense of security- we don’t see it, so why does it matter? Of course gathering data to support or refute this view point is inherently difficult, considering the ubiquitous use of RT as standard of care in many cancers plus the different delivery modalities and varying treatment protocols used. This lecture will explore the biology behind the pro-metastatic effects of RT, whether the weight of pre-clinical evidence is enough to indicate clinical relevance, and finally the potential new therapeutic window that it presents. SP-0003 Total neoadjuvant therapy in rectal cancer: When, why, how C. Marijnen 1 1 Netherlands Cancer Institute and Leiden University Medical Center, Radiation Oncology, Amsterdam and Leiden, The Netherlands Abstract Text Until recently, the standard of care for locally advanced rectal cancer (LARC) consisted of neoadjuvant chemoradiotherapy, followed by surgery according to the total mesorectal excision principles. This strategy has decreased the rates of local recurrences below 10% at 5 years. To improve quality of life, interest in organ preservation has increased, even in patients with locally advanced disease. Unfortunately, distant recurrences still remain a problem, with 5-year disease free survival rates of about 65% for locally advanced rectal cancer patients. The beneficial effect of postoperative adjuvant chemotherapy in rectal cancer is limited, especially after neoadjuvant (chemo)radiotherapy (CRT). One possible explanation is the poor compliance to chemotherapy after major surgery. In addition, the long interval between diagnosis and start of postoperative chemotherapy may facilitate outgrowth of micrometastases. Introducing chemotherapy before surgery, may therefore improve compliance and efficacy. Chemotherapy in a total neoadjuvant treatment (TNT) regimen can be given either as induction or as consolidation chemotherapy. In the last decade, several large, randomized trials have been performed in order to prove the beneficial effect of TNT. The Polish, STELLAR and RAPIDO trial evaluated regimens with short course RT (5x5 Gy) combined with consolidation chemotherapy and compared this with standard CRT with or without adjuvant chemotherapy1–3. In contrast, the PRODIGE 23 trial compared CRT combined with consolidation chemotherapy with standard CRT followed by adjuvant chemotherapy 4. Furthermore, the CAO/ARO/AIO-12 and OPRA study evaluated the difference between induction and consolidation chemotherapy in combination with CRT5,6. In general, it can be concluded that TNT appears to improve disease free survival (DFS) in some studies (RAPIDO, PRODIGE 23), but not in others (STELLAR, Polish study) when compared to standard CRT. Overall survival (OS) benefit was not seen in any of these studies. The comparison between induction and consolidation chemotherapy did not reveal a difference in DFS or OS. However, all studies comparing TNT with standard chemoradiotherapy demonstrated a significant increase in the number of patients that achieved a pathological complete response (pCR). This was confirmed in a recent meta-analysis7 and may open a window of opportunity for organ preservation in this locally advanced patient group. Additionally, consolidation chemotherapy after CRT seems more effective in achieving a pCR than induction chemotherapy before CRT. Despite these results, the optimal treatment strategy is still not clear. All above mentioned trials used different chemotherapy regimens, with variation in the number of courses as well as in the choice for doublet or triplet therapy. Also, the interval from start of treatment to evaluation varied in the different trials, hampering a firm conclusion about the best strategy. Given that no improvement in overall survival is observed in any of the trials, one has to be cautious about the increase in toxicity that is unavoidable with intensified treatment. The optimal neoadjuvant chemotherapy should therefore be balanced between efficacy and toxicity. Adequate patient selection is a prerequisite in this neoadjuvant setting to avoid unneccessary overtreatment and toxicity. Further insight in optimal strategy, patient selection and toxicity profiles will be provided during this talk. Teaching Lecture: Total neoadjuvant therapy in rectal cancer: When, why, how

S2

Saturday 13 May

ESTRO 2023

Referrences 1. Bujko, K. et al. Long-course oxaliplatin-based preoperative chemoradiation versus 5 × 5 Gy and consolidation chemotherapy for cT4 or fixed cT3 rectal cancer. Ann. Oncol. 27, 834–842 (2016). 2. Bahadoer, R. R. et al. Short-course radiotherapy followed by chemotherapy before total mesorectal excision (TME) versus preoperative chemoradiotherapy, TME, and optional adjuvant chemotherapy in locally advanced rectal cancer (RAPIDO). Lancet Oncol. 22, 29–42 (2021). 3. Jin, J. et al. Multicenter, Randomized, Phase III Trial of Short-Term Radiotherapy Plus Chemotherapy Versus Long- Term Chemoradiotherapy in Locally Advanced Rectal Cancer (STELLAR). J. Clin. Oncol. 40, 1681–1692 (2022). 4. Conroy, T. et al. Neoadjuvant chemotherapy with FOLFIRINOX and preoperative chemoradiotherapy for patients with locally advanced rectal cancer (UNICANCER-PRODIGE 23). Lancet Oncol. 22, 702–715 (2021). 5. Fokas, E. et al. Randomized Phase II Trial of Chemoradiotherapy Plus Induction or Consolidation Chemotherapy as Total Neoadjuvant Therapy for Locally Advanced Rectal Cancer: CAO/ARO/AIO-12. J. Clin. Oncol. JCO.(2019). 6. Garcia-Aguilar, J. et al. Organ Preservation in Patients with Rectal Adenocarcinoma Treated with Total Neoadjuvant Therapy. J. Clin. Oncol. 18, (2022). 7. Zhang, X., Ma, S., Guo, Y., Luo, Y. & Li, L. Total neoadjuvant therapy versus standard therapy in locally advanced rectal cancer: A systematic review and meta-analysis of 15 trials. PLoS One 17, e0276599 (2022).

Teaching Lecture: Role of PET/CT for treatment planning optimisation in salvage prostate radiotherapy

SP-0004 Role of PET/CT for treatment planning optimisation in salvage prostate radiotherapy S. Supiot 1 1 Nantes Université, Radiation Oncology, Saint Herblain, France

Abstract Text Following radical treatment of localized prostate cancer, up to 30% of patients may relapse. At relapse, PET/CT using PSMA, Choline or Fluciclovine plays a major role in defining the site of relapse and therefore could modify radiotherapy prescription in terms of indication, dose or volume. We will discuss the role of PET/CT-guided radiotherapy as a salvage treatment in different clinical situations: prostate bed relapse, pelvic lymph node relapse, distant metastases and relapse in a previously irradiated region. Following prostatectomy, salvage prostate bed radiotherapy is advocated if the PSA rises above 0.2 ng/ml, and ideally below 0.5 ng/ml. In approximately 50% of cases, PSMA PET/CT can determine the site of relapse, frequently within the prostate bed. Is there a role for radiotherapy-dose intensification in macroscopic prostate bed relapse? As shown in the SAKK 09/10 trial, increasing the total dose to the prostate bed up to 70 Gy increases toxicity rates but does not improve biochemical relapse-free survival. However, retrospective series suggest that boosting the dose to the macroscopic nodule could improve biochemical control without increasing toxicity. Another intensification strategy is to combine salvage radiotherapy and radiosensitizing drugs such as novel androgen-receptor targeting agents. Ongoing trials will help determine the best strategy of radiotherapy in macroscopic prostate bed relapses. Other frequent sites of relapse following radical treatment are pelvic lymph nodes. High dose radiotherapy targeting oligoreccurent pelvic lymph nodes, using SBRT or elective pelvic nodal irradiation may increase tumor control at the cost of limited toxicity. The Oligopelvis GETUG P12 trial is a randomized phase 3 trial that compares 6-months Androgen – Depriving Therapy (ADT) alone to ADT + elective pelvic radiotherapy. The STORM PEACE 5 trial will determine if a boost dose to the PET/CT defined lymph nodes can increase tumor control. Early toxicity results of the STORM PEACE 5 trial did not show any increased toxicity and efficacy results are eagerly awaited. Prostate cancer may also relapse distantly to non-pelvic lymph nodes, bones or less frequently to visceral sites. Randomized phase 2 trials such as SABR-Comet, Oriole or Stomp, showed that SBRT targeting oligorecurrent metastases could delay the introduction of systemic treatments and increase progression-free survival. Several randomized phase 3 studies are ongoing, in order to prove that adding metastases-targeted SBRT to systemic treatment can improve survival. The rather recent advent of PET-CT tracers lead also to the discovery of local relapses within previously irradiated areas, such as the prostate or the prostate bed. In order to delay the need for a systemic treatment for these local relapses, salvage local therapies (surgery, cryotherapy, HIFU…) have been developed. More recently salvage reirradiation using brachytherapy or SBRT was shown to be feasible despite manageable toxicity, in small series of patients. Ongoing phase I/II trials will help determine the best radiotherapy strategies in theses clinical situation (dose, fractionation) and should provide prospective evidence of efficacy. To conclude, the development of novel PET/CT radiotracers completely changed staging of prostate cancer. However, the potential benefits of novel PET/CT radiotracers to improve the efficacy of radiotherapy remain to be determined in prospective randomized phase 3 trials. SP-0005 Pulmonary SBRT technical Practice: Results of the 2022 ESTRO survey A. Scaggion 1 , A. Carver 2 , K. Karlsson 3 , E. Dalqvist 3 , D. Jurado Bruggeman 4 , F.R. Giglioli 5 , S. Warren 6 , V. Staykova 7 , A. Jenko 8 , A. Swinnnen 9 , O. Blank 10 , N. Jornet 11 , P. Pietro 12 1 Veneto Institute of Oncology IOV - IRCCS, Medical Physics Department, Padova, Italy; 2 University Hospitals Birmingham NHS Foundation Trust, Department of Medical Physics, Birmingham, United Kingdom; 3 Karolinska University Hospital, Radiotherapy Physics and Engineering, Medical Radiation Physics and Nuclear Medicine, Stockholm, Sweden; 4 Institut Català d’Oncologia, Medical Physics and Radiation Protection Department, Girona, Spain; 5 AOU Città della Salute e della Scienza, Medical Physics Unit, Torino, Italy; 6 Northern Centre for Cancer Care, Freeman Hospital, Department of Medical Physics, Newcastle Upon Tyne, United Kingdom; 7 Guy's and St Thomas' NHS Foundation Trust, Radiotherapy Physics, London, United Kingdom; 8 Institute of Oncology Ljubljana, Department of Radiotherapy, Ljubljana, Slovenia; 9 GROW School for Oncology, Maastricht University Medical Centre+, Department of Radiation Oncology (Maastro), Maastricht, The Netherlands; 10 University Medical Center Schleswig-Holstein, Department of Radiation Oncology, Kiel, Germany; 11 Hospital Teaching Lecture: Survey results and systematic review of the dosimetry information in papers on SBRT clinical trials