Does short-term androgen deprivation substitute for radiation dose in the treatment of high-risk prostate cancer?

Abstract

Purpose Randomized trials have corroborated the clinical benefit of adding androgen deprivation (AD) to radiotherapy (RT) in the treatment of high-risk prostate cancer. Another competing strategy is to escalate the RT dose using three-dimensional conformal RT (3D-CRT). In this analysis, we asked whether the addition of short-term AD (STAD) (≤6 months) to RT in the treatment of high-risk (prostate-specific antigen >20 ng/mL, Gleason score 8–10, or T3-4) prostate cancer is an effective substitute for dose escalation. Methods and materials Between March 1, 1990 and November 30, 1998, 296 high-risk prostate cancer patients were treated with 3D-CRT alone ( n = 206) or in combination with STAD ( n = 90). The patient characteristics were median age 68 years, median follow-up 58 months, pretreatment initial prostate-specific antigen 21.8 ng/mL, RT dose 75 Gy, STAD duration 3 months, and time off STAD 64 months. The impact of STAD with respect to dose was examined using univariate analysis for dose ranges of <75 Gy and ≥75 Gy. Stepwise Cox proportional hazards regression multivariate analysis was performed to determine independent correlates of freedom from biochemical failure (bNED), freedom from distant metastasis (FDM), and overall survival. In a separate matched-pair analysis ( n = 44 per group), those treated to <75 Gy + STAD (Group A) were compared with those who received ≥75 Gy alone (Group B). Results On univariate analysis, the addition of STAD had no impact on bNED, FDM, or overall survival in either dose group. On multivariate analysis, initial prostate-specific antigen level, palpation T stage, and RT dose were significant correlates of bNED. For FDM and overall survival, the significant covariates were palpation T stage and Gleason score, respectively. Finally, in matched-pair analysis, the higher RT dose group had a significantly greater bNED rate at 5 years (Group A 35% vs. Group B 57%, p = 0.0190). Conclusion Our data suggest that STAD, as used here (median 3 months), is not a substitute for RT dose in the treatment of high-risk prostate cancer. RT dose is an essential element in the treatment of high-risk prostate cancer.