Importance: Optimizing radiation therapy techniques for localized prostate cancer can affect patient outcomes. Dose escalation improves biochemical control, but no prior trials were powered to detect overall survival (OS) differences.
Objective: To determine whether radiation dose escalation to 79.2 Gy compared with 70.2 Gy would improve OS and other outcomes in prostate cancer.
Design, setting, and participants: The NRG Oncology/RTOG 0126 randomized clinical trial randomized 1532 patients from 104 North American Radiation Therapy Oncology Group institutions March 2002 through August 2008. Men with stage cT1b to T2b, Gleason score 2 to 6, and prostate-specific antigen (PSA) level of 10 or greater and less than 20 or Gleason score of 7 and PSA less than 15 received 3-dimensional conformal radiation therapy or intensity-modulated radiation therapy to 79.2 Gy in 44 fractions or 70.2 Gy in 39 fractions.
Main outcomes and measures: Time to OS measured from randomization to death due to any cause. American Society for Therapeutic Radiology and Oncology (ASTRO)/Phoenix definitions were used for biochemical failure. Acute (≤90 days of treatment start) and late radiation therapy toxic effects (>90 days) were graded using the National Cancer Institute Common Toxicity Criteria, version 2.0, and the RTOG/European Organisation for the Research and Treatment of Cancer Late Radiation Morbidity Scoring Scheme, respectively.
Results: With a median follow-up of 8.4 (range, 0.02-13.0) years in 1499 patients (median [range] age, 71 [33-87] years; 70% had PSA <10 ng/mL, 84% Gleason score of 7, 57% T1 disease), there was no difference in OS between the 751 men in the 79.2-Gy arm and the 748 men in the 70.2-Gy arm. The 8-year rates of OS were 76% with 79.2 Gy and 75% with 70.2 Gy (hazard ratio [HR], 1.00; 95% CI, 0.83-1.20; P = .98). The 8-year cumulative rates of distant metastases were 4% for the 79.2-Gy arm and 6% for the 70.2-Gy arm (HR, 0.65; 95% CI, 0.42-1.01; P = .05). The ASTRO and Phoenix biochemical failure rates at 5 and 8 years were 31% and 20% with 79.2 Gy and 47% and 35% with 70.2 Gy, respectively (both P < .001; ASTRO: HR, 0.59; 95% CI, 0.50-0.70; Phoenix: HR, 0.54; 95% CI, 0.44-0.65). The high-dose arm had a lower rate of salvage therapy use. The 5-year rates of late grade 2 or greater gastrointestinal and/or genitourinary toxic effects were 21% and 12% with 79.2 Gy and 15% and 7% with 70.2 Gy (P = .006 [HR, 1.39; 95% CI, 1.10-1.77] and P = .003 [HR, 1.59; 95% CI, 1.17-2.16], respectively).
Conclusions and relevance: Despite improvements in biochemical failure and distant metastases, dose escalation did not improve OS. High doses caused more late toxic effects but lower rates of salvage therapy.
Trial registration: clinicaltrials.gov Identifier: NCT00033631.