ESTRO 36 Abstract Book

S711 ESTRO 36 2017 _______________________________________________________________________________________________

Material and Methods The demographics, disease metrics, RTOG graded toxicity and outcome data for 42 patients receiving prostate and pelvic node radiotherapy in our institution over a 2 year period were retrospectively collected. Dosimetric data were captured including method of treatment delivery: static intensity modulated radiotherapy (IMRT) or volumetric modulated arc therapy (VMAT); dose to prostate and pelvic node volume, as well as a single dose level indicating normal tissue exposure (V50 to bowel, rectum and bladder, that is volume of normal tissue of each receiving ≥50Gy). Results The median age was 64 years. 88.1% of patients had Gleason grade ≥8 cancer and 78.6% had local staging ≥T3a. 52.4% of patients were N0 with the remaining 47.6% N1; 1 patient had M1a disease. Treatment was by IMRT in 61.9% of patients and by VMAT in 38.1%. All patients received 74 Gy to prostate. Dose to pelvic nodes was 60Gy in 78.6%, 55Gy in 19% and 56Gy in 1 patient. There was no significant difference in nodal dose received by IMRT vs VMAT groups. All patients had neo-adjuvant and adjuvant hormone therapy. Median follow up was 37 months. Acute bowel toxicity (RTOG) was <2 in 73.8% and maximally =2 in 26.2%. Late bowel toxicity was <2 in 83.3%, and maximally =2 in 16.7% Acute urinary toxicity was <2 in 85.7%, =2 in 7.1% and maximally 3 in 7.1%. Late urinary toxicity was <2 in 59.5%, =2 in 35.7% and maximally 3 in 4.8%. Endoscopy rates during follow up were low: 7 patients had lower GI endoscopy with radiation proctitis confirmed in 5; 8 patients had cystoscopy with radiation related mucosal changes in 3. 14.3% of patients have experienced biochemical failure during follow up. V50 rectum and bladder are significantly lower in patients treated by VMAT versus IMRT; V50 rectum by VMAT = 48.81% vs by IMRT = 56.19% p=0.017; V50 bladder by VMAT = 46.88% vs by IMRT = 58.85% p=0.010. This has not translated into any significant difference in acute or late toxicities between the groups split by treatment modality. No significance difference was seen between V50 bowel in VMAT vs IMRT treated patients. Conclusion In high-risk N0 and N1 prostate cancer, treatment by advanced conformal radiotherapy to prostate and pelvis is associated with acceptable levels of toxicity and good biochemical control at 37 months. There is evidence of a dosimetric advantage with VMAT over static field IMRT. EP-1341 Pelvic SABR with HDR boost in intermediate and high risk prostate cancer (spare): early results H.B. Musunuru 1 , A. Deabreu 1 , M. Davidson 1 , A. Ravi 1 , J. Hlou 1 , L. Ho 1 , P. Cheung 1 , D. Vesprini 1 , S. Liu 1 , W. Chu 1 , H. Chung 1 , L. Zhang 1 , A. Loblaw 1 1 Odette Cancer Centre- Sunnybrook Hospital- University of Toronto, Radiation Oncology, Toronto, Canada Objective ASCENDE-RT has provided level 1 evidence supporting the use of androgen deprivation therapy (ADT), external beam radiotherapy and brachytherapy boost in intermediate- and high-risk prostate cancer. The objectives of this study are to report early toxicity and quality of life (QOL) outcomes in patients treated on a hybrid protocol using five-fraction pelvic stereotactic ablative radiotherapy (SABR) with a MRI dose painted HDR brachytherapy boost (HDR-BT). Material and Methods A phase I/II study was performed where intermediate (IR) and high-risk (HR) prostate cancer patients received HDR- BT 15Gy in single fraction to the prostate and up to 22.5Gy to the MRI nodule. Gantry-based 25Gy SABR was delivered to pelvis, seminal vesicles and prostate in 5 weekly fractions. ADT was used for 6-18 months. Common Terminology Criteria for Adverse Events version 3.0 was used to assess toxicities. QOL was captured using EPIC Purpose or

increased sparing of organs at risk, based on the promising Japanese results and first Italian data from CNAO. The aim of this retrospective study was to identify the biochemical progression-free survival and the toxicity profile of localized high-risk PCa patients treated with external beam radiation therapy (EBRT). These results will constitute a benchmark for a prospective “mixed beam” trial: a boost with carbon ions followed by a pelvic photon intensity modulated radiotherapy (NCT 02672449, registered at clinicaltrials.gov). Material and Methods We retrospectively reviewed the data of 76 patients treated in our Institution with photon EBRT according to the inclusion criteria of the forthcoming “mixed beam” trial: cT3a and/or serum prostate-specific antigen >20 ng/mL and/or Gleason score of 8-10, cN0 cM0. Toxicity, biochemical and clinical progression-free survival were assessed. Results Seventy-six patients treated between 05/2010 and 12/2014 fulfilled our criteria. Median age, initial PSA and Gleason score were 74.9 years, 26.4 ng/mL and 8, respectively. Prostate and vesicles or prostate and pelvis were irradiated in 46 and 30 patients, respectively, using intensity modulated radiation therapy. Moderate hypofractionation was employed (Fox Chase regimen), with a median dose of 70.2 Gy (2.7 Gy for 26 fractions). In 61 patients (80.3%) androgen deprivation therapy (ADT) was added. The median follow-up was 30.2 months (range 7.2-61.1 months). Biochemical progression was observed in 22 patients (28.9%) after a median time of 20.2 months (range: 5- 58.1) from the end of EBRT. Sixteen patients had clinical progression, always preceded by biochemical progression. Fifty-seven patients (75.0%) are alive with no evidence of disease, 13 patients (17.1%) are alive with clinically evident disease, 6 patients (7.9%) died (3 for PCa). No grade higher than 2 acute and late toxicity, including urinary and rectal complications, was reported. Conclusion Our results suggest that a more aggressive treatment is necessary. Local treatment intensification based on the “mixed beam” approach combining carbon ions, with its known radiobiological advantages, and photons might really represent a promising strategy in the high-risk PCa and it will be investigated with our prospective clinical trial. EP-1340 Comparing dosimetry and toxicity of 5-field IMRT versus VMAT for prostate & pelvic nodal irradiation P. Turner 1 , S. Jain 1 , D. Mitchell 2 , J. Harney 2 , F. Houghton 2 , J. McAleese 2 , D. Stewart 2 , A. Hounsell 1 , D. Irvine 3 , G. Corey 2 , K. Tumelty 2 , K. Thompson 4 , J. O'Sullivan 1 1 Centre for Cancer Research and Cell Biology- Queen's University of Belfast, Advanced Radiotherapy Group, Belfast, United Kingdom 2 Northern Ireland Cancer Centre, Uro-oncology, Belfast, United Kingdom 3 Northern Ireland Cancer Centre, Radiotherapy Physics, Belfast, United Kingdom 4 Queen's University of Belfast, School of Medicine, Belfast, United Kingdom Purpose or Objective There is emerging evidence supporting the use of prostate and pelvic nodal irradiation in high-risk localised prostate cancer. Recent evidence also suggests a role for local prostate irradiation in metastatic prostate cancer. It is therefore timely to assess different methods of delivering pelvic radiotherapy from the point of view of dosimetry and real world toxicity.