Effects of dose-escalated radiotherapy in combination with long-term androgen deprivation on prostate cancer.

OBJECTIVE: We aimed to examine the effects of a dose escalation for prostate cancer patients receiving long-term androgen deprivation therapy (ADT). METHODS: A retrospective analysis of 605 patients treated with radiotherapy (RT) and long-term ADT (National Comprehensive Cancer Network criteria-defined intermediate-risk, minimum 10 months; high-risk and very-high-risk, minimum 20 months) was performed. The median ADT time was 31 months. Cox's proportional hazards models were used to compare biochemical disease-free survival (bDFS), clinical relapse-free survival (cRFS) and overall survival (OS) between the ≥70, <78 Gy group and 78 Gy group in a univariate analysis and to assess the effects of the dose escalation on bDFS in a multivariate analysis. RESULTS: After a median follow-up of 70 months, 5-year bDFS was significantly better in the 78 Gy group than in the ≥70, <78 Gy group [96 vs 83%; hazard ratio 3.6 (95% confidence interval 2.2-6.1); p < 0.001]. 5-year cRFS and OS were similar between the two groups. The multivariate analysis showed that RT dose was still an independent prognostic factor of bDFS (p = 0.005). CONCLUSION: The results of the present study suggest that dose escalations result in significant improvements in bDFS, even when used in combination with long-term ADT. A longer follow-up is needed to clarify the effects of dose escalations on cRFS and OS. Advances in knowledge: It remains unclear whether high-dose RT is necessary for improving the outcomes of patients receiving long-term ADT. The results suggest that dose escalations result in significant improvements in biochemical control.