ESTRO 38 Abstract book

S260 ESTRO 38

local recurrence); spontaneous healing was seen in 3/3 patients of S-IMRT and in 9/14 of A-DPBN. Post-hoc analysis revealed more grade ≥3 late mucosal toxicity in active smokers (29% vs. 3%, p =0.005) and alcohol drinkers (33% vs. 13%, p =0.024) at diagnosis. For grade ≥4 late mucosal toxicity, comparable results were observed in active smokers at diagnosis (19% vs. 0%, p =0.013) but not in active alcohol drinkers at diagnosis. There was no patient with grade 3 late dysphagia or xerostomia, but 1 patient presented with grade 4 dysphagia in S-IMRT due to esophageal stenosis (primary hypopharyngeal carcinoma). Conclusion Superior local control was achieved with A-DPBN compared to standard-IMRT, at the cost of more late grade ≥3 mucosal toxicity in active smokers/drinkers at diagnosis. An appropriately powered multicenter phase-3 trial comparing A-DPBN with S-IMRT in non-smokers could lead to better OS or disease-free survival without high rates of mucosal ulcers. OC-0505 Evidence-based practice in the global setting: an international survey of hypofractionation D. Rodin 1 , M. Osama 2 , B. Tawk 3 , S. Grover 4 , F. Moraes 5 , M.L. Yap 6 , E. Zubizarreta 7 , Y. Lievens 8 1 Princess Margaret Cancer Centre, Department of Radiation Oncology, Toronto, Canada; 2 University of Texas Southwestern Medical Center, Department of Radiation Oncology, Dallas, Usa ; 3 Heidelberg and German Cancer Consortium, German Cancer Research Center, Heidelberg, Germany; 4 University of Pennsylvania, Department of Radiation Oncology, Philadelphia, USA ; 5 Kingston General Hospital, Department Of Oncology, Kingston, Canada ; 6 Ingham Health And Medical Research Institute, Liverpool Cancer Therapy Centre- Macarthur Cancer Therapy Centre, Liverpool, Australia; 7 International Atomic Energy Agency, Section of Applied Radiation Biology And Radiotherapy, Vienna, Austria ; 8 Ghent University Hospital, Department of Radiation Oncology, Ghent, Belgium Purpose or Objective Multiple large clinical trials have established the equivalence or non-inferiority of hypofractionated radiotherapy compared to conventionally fractionated treatment. The objective of this study is to determine real-world variations in the adoption of hypofractionation across different geographic regions and practice settings for cancers of the breast, prostate, and cervix, and for bone metastases, and barriers and facilitators to such adoption. Material and Methods An anonymous, electronic survey was distributed internationally from January to December 2018 in English, Spanish, and Mandarin to radiation oncology consultants through the ESTRO Global Impact of Radiotherapy in Oncology initiative. There were 2,259 respondents from Europe (56%), Asia Pacific (19%), Middle East (5%), 12% Latin America, (12%), North America (6%), and Africa (2%). This survey assessed preference for hypofractionation and specific fractionation regimens across 4 disease sites (breast, prostate, and cervical cancer, and bone metastases) in curative and palliative scenarios. Perceived barriers and facilitators to adoption were evaluated. In regression analyses, hypofractionation preference was defined as the use of hypofractionation for >75% of patients within each disease site and in >50% of clinical scenarios overall. Results Hypofractionation preference was more common in node- negative than in node-positive breast cancer (83% vs 46%, respectively; p<0.001), in low- and intermediate- vs. high- risk prostate cancer or that requiring pelvic irradiation (56% vs. 32%, respectively; p=0.00001); hypofractionation

Results Table 1 shows an imbalance in site distribution. Median follow-up was 25 months. Better local control was achieved in A-DPBN: 1- and 2-year local control were 91% and 88% vs. 78% and 75% in A-DPBN vs. S-IMRT ( p =0.033). One- and 2 year regional control were equal in A-DPBN vs. S-IMRT: 86% and 84% vs. 84% and 82%, respectively ( p =0.8). One- and 2 year OS were equal in A-DPBN vs S-IMRT: 85% and 80% vs. 90% and 70%, respectively ( p =0.2). There was no difference in grade ≥3 acute dermatitis, dysphagia or mucositis between both arms. More grade 3 acute dysphagia was observed in patients with concomitant chemotherapy (13/42; 49% vs. 3/41; 22%, p =0.016) and depended from site (oral cavity 100%, oropharynx 42%, larynx 25% and hypopharynx 28%, p =0.036). We observed more grade ≥3 late mucosal toxicity (33% vs. 7%, p =0.003) and grade ≥4 late mucosal toxicity (19% vs. 5%, p =0.047) in A-DPBN than S-IMRT. One grade 5 toxicity was observed in A- DPBN (mucosal blow-out in absence of