A phase II study of localized prostate cancer treated to 75.6 Gy with 3D conformal radiotherapy

Abstract

Background and purposeTo prospectively evaluate toxicity, biochemical failure-free survival (bFFS) and biopsy-proven local control for prostate cancer patients treated with 75.6Gy in 42 fractions using 6-field conformal radiotherapy to prostate alone. Patients and methodsFrom 1997 to 1999, 140 patients with T1-2NxM0, Gleason score ≤8, and PSA ≤20ng/ml prostate cancer were assessed using Radiation Therapy Oncology Group acute and late toxicity scores. bFFS was determined for 120 patients treated without hormones. Post-treatment prostate biopsies were performed at a median of 3 years and a late toxicity questionnaire was administered at a median of 5 years. ResultsClinically important acute toxicities were gastrointestinal (GI) grade 2: 22% and 3: 0%, and genitourinary (GU) grade 2: 24% and 3: 2%. Late physician-assessed toxicities were GI ≥grade 2: 2%, and GU ≥grade 2: 1%. The 3-year bFFS of patients failure-free before biopsy was 93% (95% CI: 83–100) from a negative biopsy and 22% (95% CI: 0–56) from a positive biopsy (P=0.001). Patients reported significantly more late toxicity than physicians (GI: P=0.003, GU: P<0.001). At 5.0 years median follow-up, cause-specific survival was 98% (95% CI: 96–100), overall survival was 91% (95% CI: 86–97), and bFFS was 55% (95% CI: 45–64). Conclusions75.6Gy caused modest levels of acute and late toxicity. Three-year biopsies predicted subsequent biochemical outcome.