ESTRO 2023 - Abstract Book

S770

Monday 15 May 2023

ESTRO 2023

Results All patients in the study tolerated the treatment fairly well with mostly mild or no acute GU and GI toxicity (CTCAE v4.0 scale) and no differences between arms (p=0.227 and p=0.441). Grade-3 acute GU toxicity was observed in only one patient (urinary retention) (arm B). Late grade 2 GU toxicity was observed in 20.7% and 22.5% of patients in arms A and B, respectively; with only one case of grade-3 GU toxicity (obstructive symptoms) observed in arm A at month 18. Late GI toxicity remained mild and similar in both arms, with no grade-3 events, < 4% grade-2, and grade-0 in more than 70% of patients. The 5-year grade 2 GU toxicity-free survival was 75.9% and 76.1% for arms A and B, respectively (p=0.945), while the 5-year grade 2 GI toxicity-free survival was 89% and 91.9% for arms A and B, respectively (p=0.596). No changes in EORTC QLQ-PR25 scores were observed in both arms for GU, GI, and sexual domains at 5-year follow-up compared to baseline. Furthermore, mean IPSS scores were also similar at last follow-up compared to baseline (6.4 vs 7.8, for arm A and 7.1 vs 7.5, for arm B). Median PSA values decreased over time from a median value of 8.3 ng/ml and 7.0 ng/ml at baseline to 0.28 ng/ml and 0.37 ng/ml at last follow-up in arms A and B, respectively. At the last follow-up, biochemical failure was observed in 14 patients in the EOD arm and in 7 patients in the QW arm with a 5-year biochemical relapse-free survival rate of 92.2% and 93% for arms A and B, respectively (p=0.13). Four patients in each arm presented a local relapse, while a nodal relapse-only was observed in one patient treated EOD. At last follow-up, two patients in arm A and one in arm B developed distant metastases. Conclusion SBRT for PCa with a 10% dose reduction to urethra was associated with a minimal impact on urinary function and quality of life regardless of a EOD or QW fractionation schedule. Biochemical control so far, has been encouraging and much alike in both study arms, though longer follow-up is probably needed to assess the true value of overall treatment time on disease outcome. OC-0924 Prostate RT In high risk or N+ Moderate vs Extreme hypofractionation (PRIME): An Interim analysis V. Murthy 1 , P. Maitre 1 , M. Arunsingh 2 , R. Phurailatpam 3 , R. Mhatre 3 , B. Arun 4 , G. Panigrahi 1 , P. Singh 1 , S. Menon 5 , G. Prakash 6 , M. Pal 6 , A. Arora 6 , A. Katdare 7 , A. Agrawal 8 , V. Rangarajan 8 , S. Kannan 9 , I. Mallick 2 1 Tata Memorial Centre, Homi Bhabha National Institute, Radiation Oncology, Mumbai, India; 2 Tata Medical Center, Radiation Oncology, Kolkata, India; 3 Tata Memorial Centre, Homi Bhabha National Institute, Medical Physics, Mumbai, India; 4 Tata Medical Center, Medical Physics, Kolkata, India; 5 Tata Memorial Centre, Homi Bhabha National Institute, Pathology, Mumbai, India; 6 Tata Memorial Centre, Homi Bhabha National Institute, Surgery, Mumbai, India; 7 Tata Memorial Centre, Homi Bhabha National Institute, Radiodiagnosis, Mumbai, India; 8 Tata Memorial Centre, Homi Bhabha National Institute, Nuclear Medicine and Molecular Imaging, Mumbai, India; 9 Tata Memorial Centre, Homi Bhabha National Institute, Clinical Research Secretariat, Mumbai, India Purpose or Objective Safety of SBRT for high-risk and node-positive prostate cancer is not yet established. We report 90-day toxicity and QOL from the pre-planned interim analysis of the ongoing phase III, multicentric, randomised PRIME trial (NCT03561961). Materials and Methods Patients with NCCN high-risk or node-positive prostate adenocarcinoma (non-regional nodes or distant metastases excluded) are being randomised 1:1 to moderate (MHRT) or extreme (SBRT) hypofractionated RT. Patients in the MHRT arm received 68Gy/25# or 62Gy/20# to prostate, 50Gy/25# or 44Gy/20# to the pelvis, and in the SBRT arm 36.25Gy/5# with 25Gy/5# to the pelvis. ADT was prescribed for at least 24 months without systemic intensification. Toxicity using CTCAE v5.0, and QOL using EORTC QLQC-30 and PR-25 was recorded at baseline, RT completion, at 3-6 weeks, and then 3-6 monthly, with a threshold of 10 points change in the mean QOL scores for minimal clinically important change (MCIC). While the trial targets a sample of 464 for primary endpoint of 5-year biochemical failure-free survival, we report the cumulative 90-day toxicity and QOL for patients randomised till a pre-planned interim analysis. Results Total 307 randomised patients (N0=241, N1=66) were analysed, MHRT=153 and SBRT=154. Of these, 296 received RT and were eligible for toxicity reporting. Table 1 shows the cumulative 90-day urinary (GU) and gastrointestinal (GI) toxicities. Grade 3 GU toxicity was low, and observed in 3 patients (SBRT=1, MHRT=2), GI in 2 patients (1 each in MHRT and SBRT), without any grade 4 toxicity. Grade 2 acute GU and GI toxicities were similar for MHRT and SBRT (GU 33.1% vs 31.8%, p=0.5; GI 17.2 vs 15.2, p=0.9). Change in the mean QOL scores before and after RT for urinary symptoms was 9.4 for MHRT (26.6 to 36.0) and 5.1 for SBRT (27.5 to 32.6). For GI symptoms, the change in mean QOL was 1.9 for MHRT (7.4 to 9.3) and 0 for SBRT (6.7 to 6.7). Both of these were below the pre-defined threshold of MCIC. Table 1: Cumulative 90-day urinary and gastrointestinal toxicities [*CTCAE grade 3 toxicity in parentheses, others grade 2]