Moderate dose escalation in three-dimensional conformal localized prostate cancer radiotherapy: single-institutional experience in 398 patients comparing 66 Gy versus 70 Gy versus 74 Gy.

PURPOSE: To evaluate the clinical outcome in prostate cancer patients treated at one single institution by the implementation of moderate dose escalation. PATIENTS AND METHODS: A total of 398 patients with histologically verified localized prostate cancer (T1-3 Nx0 Mx0) were treated by three-dimensional conformal radiotherapy with/without additional hormonal therapy. Risk group distribution was as follows: 106 low-risk (27%), 164 intermediate-risk (41%), and 128 high-risk (32%) patients. Total local dose was increased from 66 Gy (1994-1998) to 70 Gy (1998-2003) and 74 Gy (1998-2005). Biochemical no evidence of disease (bNED: ASTRO/Phoenix definition) and late gastrointestinal/urogenital side effects (EORTC/RTOG) were assessed.
RESULTS: Median follow-up was 64 months. The 5-year bNED rates according to 66 Gy, 70 Gy and 74 Gy were 37%, 64% and 63% (ASTRO), and 54%, 74% and 69% (Phoenix), respectively. In multivariate analysis, age and T-stage were significant in predicting bNED. The 5-year bNED rates (ASTRO) according to 66 Gy, 70 Gy and 74 Gy were 40%, 78% and 73% in the low-risk group, 41%, 55% and 85% in the intermediate-risk group, and 30%, 53% and 52% in the high-risk group. Intermediate-risk patients showed a significant improvement of bNED by increasing the dose up to 74 Gy. The 5-year actuarial rates of gastrointestinal/urogenital side effects grade > or = 2 were 18%/16% (66 Gy), 20%/24% (70 Gy), and 27%/28% (74 Gy).
CONCLUSION: A benefit of local doses at a level of > or = 70 Gy could be detected showing the highest increase of prostate-specific antigen control in the intermediate-risk group. The amount of patients reporting of severe late side effects is small.