ESTRO 38 Abstract book

S134 ESTRO 38

OS survival at 7 year follow-up, and the effect of hypofractionation on local failure. Results Between 2007 and 2010, 820 patients were enrolled. A total of 804 were assessable for the current evaluation. Of these, 407 were assigned hypofractionated radiotherapy (HF) and 397 conventionally fractionated radiotherapy (CF). 537 (67%) of 804 patients received concomitant androgen deprivation therapy for a median duration of 32 months (IQR 10-44). Median follow-up was 89 months. Treatment failure at 7 years was reported in 183 (89 HF vs 94 CF) of 804 patients. 7-year relapse-free survival was 71.7 % (95% CI 66.4-76.4) for patients assigned hypofractionation and 67.6% (95% CI 62.0-72.5) for conventional fractionation (p=0.52). Overall survival was 80.8 % (95% CI 76.5-84.4) in the hypofractionated group versus 77.6 % (95 % CI 73.0-81.5) in the conventional fractionated group (p=0.17). Local failure as first site of recurrence was reported in 15 in the hypofractionated arm and 25 in the conventional arm (p=0.09). For Gleason ≥ 8, a statistically significant difference in local failure free survival was found in favor of hypofractionation (p=0.003).

The primary endpoint was pathological Complete Response Rate (pCRR), defined as the proportion of pts presenting <5% of residual viable cancer cells evaluated by a Central Review Board on anonymized tumor specimen. Key secondary endpoints included negative surgical margin (R0) and general safety. Results Among the 180 randomized pts, 176 were included in the intent-to-treat full analysis set (ITT-FAS). In the ITT-FAS population, pCRR was 16.1% in Arm A vs 7.9% in Arm B (p=0.0448). R0 margin was achieved in 77.0% of pts in Arm A vs 64.0% in Arm B (p=0.0424). The limb amputation rate, another secondary outcome, was decreased by 50% in Arm A as compared to Arm B. NBTXR3 showed very good local tolerance without any modification of RT alone safety profile. In all the treated pts in Arm A, who received any amount of NBTXR3 or at least one RT dose, the IT administration of NBTXR3 caused injection-site pain in 12 (13.5%) pts. NBTXR3 was also associated with grade 3-4 acute immune reactions in 7 (7.9%) pts, but these adverse events were of short duration, manageable, and, in some cases, resolved spontaneously. Long-term efficacy and safety results will be presented. Conclusion In this study both the primary and secondary endpoints (pCRR and R0 rate, respectively) were met with a safety profile of NBTXR3 activated by RT comparable to that of RT alone. As pCR is associated with improved progression- free and overall survival, NBTXR3 activated by RT represents a new preoperative treatment option for locally advanced STS. These data support ongoing studies investigating NBTXR3 in recurrent/metastatic HNSCC or metastatic non-small cell lung cancer [NCT03589339]; HNSCC [NCT01946867; NCT02901483]; prostate cancer [NCT02805894], liver cancer [NCT02721056] and rectal cancer [NCT02465593]. OC-0272 Hyprofractionated vs conventional radiotherapy for prostate cancer: 7 yr results from the HYPROtrial L. Incrocci 1 , K. De Vries 1 , R. Wortel 1 , E. Oomen 1 , W. Heemsbergen 1 , F. Pos 2 1 Erasmus Medical Center Rotterdam Daniel den Hoed Cancer Center, Department of Radiation Oncology, Rotterdam, The Netherlands ; 2 Netherlands Cancer Institute-Antoni van Leeuwenhoek Hospital, Department of Radiation Oncology, Amsterdam, The Netherlands Purpose or Objective In the phase 3, HYpofractionated irradiation for PROstate cancer (HYPRO) trial, hypofractionated radiotherapy was compared with conventionally fractionated radiotherapy. In previous reports, we could not demonstrate the postulated superiority of hypofractionation in terms of relapse-free survival (RFS) at 5-year follow-up. The use of long-term androgen deprivation therapy in more than 60% of the patients might have obscured potential benefits of hypofractionation at 5-year follow-up. In this analysis, we provide the 7-year outcomes on biochemical failure, clinical failure, local failure and overall survival (OS). Material and Methods Patients with intermediate to high-risk localized prostate cancer (cT1-cT4NX0MX0), a PSA concentration ≤60 μg/L and a WHO performance status of 0-2, were included in 7 Dutch radiotherapy centers. Patient were randomly assigned (1:1) to hypofractionated radiotherapy of 64.6 Gy (19 fractions of 3.4 Gy, three fractions per week) or conventionally fractionated radiotherapy of 78.0 Gy (39 fractions of 2.0 Gy, five fractions per week). Based on an estimated α/β ratio for prostate cancer of 1.5 Gy, the equivalent total dose in fractions of 2.0 Gy (EQD2) was 90.4 Gy for hypofractionation versus 78.0 Gy for conventional fractionation. Primary outcomes have been previously published. This analysis will report on RFS en