Hypofractionated radiotherapy (HFRT) produces similar long-term outcomes as conventionally fractionated radiotherapy (CFRT) in patients with high-risk prostate cancer, according to phase 3 results presented at the 2022 ASTRO Annual Meeting.
The results suggest that HFRT should be considered a new standard of care for high-risk prostate cancer patients considered for primary external beam radiation therapy and long-term androgen deprivation therapy (ADT), said study presenter Tamim Niazi, MD, of Jewish General Hospital in Montreal, Canada.
The phase 3 trial (ClinicalTrials.gov Identifier: NCT01444820) included 329 patients with high-risk prostate cancer who were randomly assigned to undergo HFRT (n=164) or CFRT (n=165), each in combination with ADT.
HFRT was administered as 45 Gy in 25 fractions to the pelvis and 68 Gy in 25 fractions as a concomitant boost. CFRT was administered as 46 Gy in 23 fractions to the pelvis with 30 Gy in 15 fractions as a sequential boost. Patients also received ADT before, during, and after radiotherapy, for a total of 28 months.
At 7 years, outcomes with HFRT were noninferior to outcomes with CFRT. The 7-year overall survival rate was 81.7% with HFRT and 82% with CFRT (hazard ratio [HR], 0.92; 95% CI, 0.56-1.53; P =.76).
The 7-year prostate cancer-specific survival rate was 94.9% with HFRT and 96.4% with CFRT (HR, 1.31; 95% CI, 0.46-3.78; P =.61). The rate of biochemical failure-free survival at 7 years was 87.4% with HFRT and 85.1% with CFRT (HR, 0.89; 95% CI, 0.49-1.60; P =.69). The rate of distant metastasis-free survival was 91.5% with HFRT and 91.8% with CFRT (HR, 0.89; 95% CI, 0.41-1.90; P =.76).
There were no significant differences in late grade 1-2 gastrointestinal (GI) adverse events (AEs) between the treatment arms. There were 3 late grade 3 GI AEs in the HFRT arm only. There were no late grade 4 GI AEs in either arm.
The incidence of late grade 1 genitourinary (GU) AEs was similar between the treatment arms, but the rate of late grade 2 GU AEs was significantly higher with CFRT (P =.035). There was 1 late grade 3 GU AE in the HFRT arm, and there were 3 in the CFRT arm. There were no late grade 4 GU AEs.
HFRT using 68 Gy in 25 fractions is as effective as CFRT using 76 Gy in 38 fractions, with similar and acceptable toxicity, Dr Niazi concluded.
Disclosures: This study was supported by Sanofi Canada. Dr Niazi disclosed relationships with AbbVie, Astellas, Bayer, Janssen, Amgen, Sanofi, AstraZeneca, TerSera, Knight Therapeutics, Paladin, Watson, Merck, and Ferring.
Niazi TM, Nabid A, Malagon T, et al. Conventional vs. hypofractionated, radiotherapy for high-risk prostate cancer: 7-year outcomes of the randomized, non-inferiority, phase 3 PCS5 trial. ASTRO 2022. October 23-26, 2022. Abstract 4.