PURPOSE: Men with Gleason score (GS) 8-10 prostate cancer (PCa) are assumed to have a very high risk of micrometastatic disease at presentation. However, local failure is also a major problem. We sought to establish the importance of more aggressive local radiotherapy to ≥80 Gy. METHODS: There were 226 men treated consecutively with RT ± ADT from 1988 to 2002 for GS 8-10 PCa. Conventional, 3D conformal, or intensity-modulated (IM) RT was used. Radiation dose was divided into three groups: 1: <75 Gy (n=50); 2: 75-79.9 Gy (n=60); or 3: ≥80 Gy (n=116). The endpoints examined included biochemical failure (BF; nadir+2 definition), distant metastasis (DM), cause specific mortality (CSM) and overall mortality (OM). RESULTS: Median follow-up was 66, 71, and 58 months for groups 1, 2 and 3. On Fine and Gray’s competing risk regression analysis, significant predictors of reduced BF were RT dose ≥80 Gy (p=0.011) and ADT duration ≥24 months (p=0.033). In a similar model of DM, only RT dose ≥ 80 Gy was significant (p=0.007). On Cox regression analysis, significant predictors of reduced OM were RT dose ≥ 80 Gy (p=0.035) and T-category (T3/4 vs. T1, p=0.041). Dose was not a significant determinant of CSM. Results for RT dose were similar in a model with RT dose and ADT duration as continuous variables. CONCLUSION: The results indicate that RT dose escalation to ≥80 Gy is associated with lower risks of BF, DM, and OM in men with GS 8-10 PCa, independently of ADT
