ESTRO 2023 - Abstract Book

S207

Saturday 13 May

ESTRO 2023

in combination with SBRT. The following combinations were identified to be associated with a clinically relevant risk of grade ≥ 3 toxicity: ipilimumab and intra-thoracic (12%) and intra-abdominal SBRT (10%), nivolumab & ipilimumab and intra- thoracic SBRT (26%), multikinase inhibitors (22%) or bevacizumab (12%) and intra-abdominal SBRT, and cetuximab and cervical SBRT (15%). The Delphi process resulted in a consensus ( ≥ 75% agreement) of 50% of the drug categories on whether to administer TT/IT on the same days as SBRT delivery. Consensus was reached to not administer anti-VEGF-antibodies, anti-EGFR-antibodies, nivolumab/ipilimumab, BRAF-/MEK-inhibitors and mTKIs on the same days of metastases-directed SBRT delivery; consensus was also reached that trastuzumab and pertuzumab can be administered on the same days as SBRT delivery. Further consensus was reached that multikinase inhibitors and BRAF/MEK-inhibitors be interrupted for a maximum of two weeks and anti-EGFR- and VEGF- antibodies and ipilimumab/nivolumab for minimum one week before/after SBRT. A consensus not to reduce radiation doses and not to change radiotherapy fractionation was reached for all TT/IT groups, irrespective of the anatomical location of SBRT. Conclusion Results of this systematic review and consensus process compile best available evidence for safe combination of SBRT and TT/IT for patients with oligometastatic cancer and aim to guide today’s clinical practice and future clinical trial design. In the presence of a paucity of high-level evidence, large international registry trials are recommended to timely generate prospective real-world data on patients receiving combination treatment. OC-0271 SBRT for spine metastases: A systematic review for preparation of an ESTRO practice guideline R.S. Guninski 1 , F. Cuccia 2 , N. Andratschke 1 , C. Belka 3 , D. Bellut 4 , M. Dahele 5 , M. Josipovic 6 , P. Mancosu 7 , G. Minniti 8 , M. Niyazi 3 , U. Ricardi 9 , P.M. af Rosenschöld 10 , A. Sahgal 11 , W. Verbakel 5 , Y.M. Tsang 12 , M. Guckenberger 1 , F. Alongi 13,14 1 University Hospital Zurich, University of Zurich, Department of Radiation Oncology, Zurich, Switzerland; 2 ARNAS Civico Hospital , Radiation Oncology Unit, Palermo, Italy; 3 University Hospital, LMU Munich, Department of Radiation Oncology, Munich, Germany; 4 University Hospital Zurich, University of Zurich, Department of Neurosurgery, Zurich, Switzerland; 5 Amsterdam University Medical Center, Department of Radiation Oncology, Amsterdam, The Netherlands; 6 Rigshospitalet, Department of Oncology, Section of Radiotherapy, Copenhagen, Denmark; 7 IRCCS Humanitas Research Hospital, Medical Physics Unit of Radiotherapy Dept., Rozzano, Italy; 8 University of Siena, Radiation Oncology Unit, Department of Medicine, Surgery and Neurosciences, Siena, Italy; 9 University of Turin, Department of Oncology, Turin, Italy; 10 Rigshospitalet, Radiation Medicine Research Center, Copenhagen, Denmark; 11 Odette Cancer Center of the Sunnybrook Health Sciences Center, Department of Radiation Oncology, Toronto, Canada; 12 Princess Margaret Cancer Centre, Radiation Medicine Program, Toronto, Canada; 13 IRCCS Sacro Cuore Don Calabria Hospital, Advanced Radiation Oncology Department Cancer Care Center, Negrar, Italy; 14 University of Brescia, Advanced Radiation Oncology Department, Brescia, Italy Purpose or Objective The role of stereotactic body radiotherapy (SBRT) for the treatment of spinal metastases is gaining in relevance as more effective systemic therapy leads to improved overall survival (OS) in selected patients with metastatic cancer. For an increasing number of patients, this shifts the goal of spinal radiotherapy from short-term palliation to long-term symptom and tumor control. As preparation for an evidence-based ESTRO guideline, we conducted a systematic review of the literature concerning SBRT for spine metastases. Materials and Methods Pubmed, Embase and Cochrane databases were interrogated and PRISMA methodology was used. Extracted data included local metastasis control, survival outcomes, pain relief, vertebral compression fracture (VCF) rates and adverse events incidence. Re-irradiation was excluded. Results Initial screening identified 1417 potential references, of which 72 studies were included in the systematic review. Sixty were retrospective and 12 prospective (n=12). Evaluated patients had a median Karnofsky performance status of 90 (range, 70-100) and oligometastatic disease in a median proportion of 40% (20-100%). The most frequent primary histologies were breast cancer, non-small cell lung cancer and renal cell cancer in 48, 46 and 39 studies, respectively. Spine SBRT was delivered using VMAT technique in 47% of the studies and Cyberknife in 18%. Daily image guided was performed in all studies (mainly CBCT in 61% of cases, ExacTrac in 10%, kV imaging in 12.5%). A median total dose of 24 Gy (18-42 Gy) was delivered in a median of 2 fractions (1-5 fractions), with a median dose per fraction of 12 Gy (6-20 Gy). With a median follow-up of 14.2 months (7-80.4 months), median local control rates after SBRT were 85% (67-100%) and 78.5% (66.2-100%) at 1- and 2-years, respectively, while 1- and 2-years OS rates were 71% (23-100%) and 58% (23-89.9%), respectively. Median overall and complete pain response rate were 87% and 51%, respectively. Pain flare was reported in 0-30% of the patients and the median incidence of VCF was 4.4% (0-34.4%). Radiation induced myelopathy was reported in 3 studies with rates ranging between 1.9% and 2.6%; in 54 out of 72 studies no myelopathy was observed. Conclusion The currently available literature indicates that in appropriately selected patients, SBRT for spinal metastases is associated with excellent pain response and local tumor control rates, with a low risk of severe adverse events. OC-0272 Organ preservation in rectal cancer: the randomised STAR-TREC phase II trial C. Marijnen 1,2 , J. de Wilt 3 , S. Bach 4 , F. Peters 1 , K. Spindler 5 , A. Appelt 6 , M. Teo 7 , V. Homer 8 , N. Abbott 9 , I. Geh 10 , S. Korsgen 11 , I. Al-Najami 12 , A. Rombouts 3 , P. Christensen 13 , A. Gilbert 14 , L. Navarro-Nunez 15 , P. Quirke 16 , N. West 17 , D. Sebag-Montefiore 18,19 1 Netherlands Cancer Institute, Radiation Oncology, Amsterdam, The Netherlands; 2 Leiden University Medical Center, Radiation Oncology, Leiden, The Netherlands; 3 Radboud University Medical Center, Surgery, Nijmegen, The Netherlands; 4 University of Birmingham, Surgery, Birmingham, United Kingdom; 5 Aarhus University Hospital, Oncology, Aarhus, Denmark; 6 University of Leeds , Leeds Institute of Medical Research , Leeds, United Kingdom; 7 Leeds Cancer Center, Clinical Oncology, Leeds, United Kingdom; 8 University of Birmingham, Cancer Clinical Trials Unit, Birmingham, United Proffered Papers: Lower GI