ESTRO 2020 Abstract Book

S347 ESTRO 2020

defined threshold. Clinician-assessed late effects were higher for the 27Gy 5-fraction schedule compared with 40Gy in 15 fractions but 26Gy in 5 fractions are as safe as the 40Gy schedule. Funding National Institute for Health Research HTA Programme - HTA (UK) (09/01/47) OC-0611 APBI with 3D-CRT vs. WBI: cosmetic and toxicity results of the prospective randomised IRMA trial B. Meduri 1 , A. Baldissera 2 , M. Stam 3 , G. Blandino 4 , L. Boersma 5 , S. Parisi 6 , M. Valli 7 , E. Koiter 8 , L. Frassinelli 1 , S. Ciabatti 2 , P. Giacobazzi 1 , A.G. Morganti 9 , R. D'amico 10 , C. Iotti 4 , F. Bertoni 11 , P.M.P. Poortmans 12 , G.P. Frezza 2 1 azienda Ospedaliero-Universitaria Di Modena, Oncology Department - Radiation Oncology Unit, Modena, Italy ; 2 ospedale Bellaria – Ausl Di Bologna, Radiotherapy Unit, Bologna, Italy ; 3 radiotherapiegroep, Radiotherapiegroep Arnhem, Arnhem, The Netherlands ; 4 ausl-Irccs Di Reggio Emilia, Radiotherapy Unit, Reggio Emilia, Italy ; 5 maastricht University Medical Centre + Mumc+, Department Of Radiation Oncology Maastro, Maastricht, The Netherlands ; 6 casa Del Sollievo Della Sofferenza, Radiotherapy Unit, S. Giovanni Rotondo Foggia, Italy ; 7 ospedale Regionale Bellinzona E Valli, Istituto Oncologico Della Svizzera Italiana, Bellinzona, Switzerland ; 8 medisch Spectrum Twente, Radiotherapy Unit, Enschede, The Netherlands ; 9 university Of Bologna, Radiation Oncology Center-Department Of Experimental- Diagnostic And Specialty Medicine, Bologna, Italy ; 10 università Di Modena E Reggio Emilia, Department Of Medical Statistic, Modena, Italy ; 11 azienda Ospedaliero-Universitaria Di Modena, Emeritus Chair Of Radiotherapy Unit, Modena, Italy ; 12 paris Sciences Et Lettres University, Marie Curie Profesor, Paris, France Purpose or Objective To report cosmetic and toxicity results in all patients enrolled in the multicentric prospective randomised phase 3 IRMA trial Material and Methods Women aged ≥ 49 years with invasive breast cancer< 3 cm, pN0-1, were randomly assigned after breast-conserving surgery to 3D-CRT accelerated partial breast irradiation (APBI) (38,5 Gy in 10 fractions twice daily) or whole breast irradiation (WBI). Patients received adjuvant systemic therapy according to institutional guidelines. Cosmetic results were assessed according to IRMA protocol parameters by both the patient and the physician. Toxicity was scored according to RTOG tables. We performed the analysis according to the treatment received Results From March 2007 to March 2019, 3309 patients were enrolled by 35 European centres. Median follow-up was 5 years. Acute G3-4 skin toxicity was rare in both treatment arms (0% PBI vs. 1,07% WBI), no further G3-4 acute toxicities were observed. Late G2-4 skin toxicity was 7,02% (APBI) vs. 8,68% (WBI) (p=0,08); G2-4 late subcutaneous tissue toxicity was 43,93% (APBI) vs 28,89% (WBI) (p<0,01) (G3-4: 2,57% vs 1%; p<0,01); G3-G4 bone toxicity was 1,03% (APBI) vs 0% (WBI) (p<0,01); further G3-4 late toxicities were rare (<0,2%). Axillary lymph node dissection (vs. sentinel node) increased G3-4 late skin toxicity (2,46% vs. 0,47%, p<0,01); no correlation of toxicity with adjuvant chemotherapy was observed. At 5 years, adverse cosmetic results (fair/poor) were: physician-reported 18,45% (APBI)

vs. 15,01% (WBI) (p=0,1); patient-reported 15,1% (APBI) vs. 10,86% (WBI) (p=0,02) Conclusion APBI with 3D-CRT was associated with an increased rate of moderate to late subcutaneous tissue and bone toxicity and with a slight decrease in patient-reported cosmetic outcome at 5 years. Longer follow-up is needed to confirm these results OC-0612 The FLAME trial: benefit of a focal boost for prostate cancer on biochemical disease-free survival L.G.W. Kerkmeijer 1,2 , V.H. Groen 1 , F.J. Pos 3 , K. Haustermans 4 , E.M. Monninkhof 5 , R.J. Smeenk 2 , M.C. Kunze-Busch 2 , H.C.J. De Boer 1 , J.R.N. Van Der Voort Van Zyp 1 , M. Van Vulpen 6 , C. Draulans 4 , L. Van Den Bergh 4 , S. Isebaert 4 , U.A. Van Der Heide 3 1 umc Utrecht, Radiation Oncology, Utrecht, The Netherlands ; 2 umc St Radboud Nijmegen, Radiation Oncology, Nijmegen, The Netherlands ; 3 the Netherlands Cancer Institute, Radiation Oncology, Amsterdam, The Netherlands ; 4 university Hospitals Leuven, Radiation Oncology, Leuven, Belgium ; 5 julius Center, Health Sciences And Primary Care, Utrecht, The Netherlands ; 6 holland Proton Therapy Center, Radiation Oncology, Delft, The Netherlands Purpose or Objective To demonstrate the superiority of a simultaneous integrated focal boost to the macroscopic visible tumor on multiparametric MRI on 5-year biochemical (PSA) disease- free survival (bDFS) in patients with localized prostate cancer treated with external beam radiotherapy (EBRT). Material and Methods A total of 571 patients with intermediate- and high-risk localized prostate cancer were enrolled in the Focal Lesion Ablative Microboost in Prostate Cancer (FLAME) phase III multicenter randomized controlled trial (NCT01168479) between November 2009 and February 2015. Patients randomized to the standard treatment arm received 77Gy in 35 fractions of 2.2Gy to the whole prostate gland. Patients in the FLAME arm received an additional integrated focal boost up to 95Gy to the macroscopic tumor, resulting in 35 fractions up to 2.7Gy. The primary endpoint was 5-year bDFS. Biochemical recurrence was defined as PSA nadir + 2 ng/mL (Phoenix criteria). Recurrent disease was defined as biochemical recurrence and/or evidence of recurrent disease on imaging. Kaplan- Meier curves were compared with the log-rank test to assess differences in bDFS, DFS, prostate cancer-specific survival (CSS) and overall survival (OS). For bDFS and DFS, patients were censored at death date or date of last follow-up. Cox regression analyses adjusted for center were applied. Analyses were performed using an intention- to-treat (primary) and per-protocol approach (secondary). Results For the present preliminary primary endpoint analysis 563 patients were included. Eight patients were excluded after randomization because they did not fulfill the inclusion criteria. Median follow-up was 71 months (range 4-113 months). Hormonal therapy was given in 66.3% and 66.5% in the standard and FLAME arm, respectively. The proportion of 5-year bDFS was 85% (38 events; 95% CI 81%- 89%) in the standard arm and 91% (21 events; 95% CI 87- 95%) in the FLAME arm (log-rank test p<0.001), as depicted in Figure 1. The proportion of 5-year DFS was 84% (42 events; 95% CI 80%-88%) in the standard arm and 90% (25 events; 95% CI 86-94%) in the FLAME arm (log-rank test p<0.001). Kaplan-Meier analyses for prostate CSS (log-rank p=0.4) and OS (log-rank p=0.5) showed no difference