May non-metastatic clinically localized castration-resistant prostate cancer after primary androgen ablation benefit from salvage prostate radiotherapy?

PURPOSE: A proportion of patients with localized prostate cancer is still treated with primary androgen deprivation therapy (PADT) alone. Some of these patients may develop a PSA rising despite castration. The purpose of this study was to retrospectively evaluate the potential benefit of external beam radiotherapy (EBRT) in this cohort. METHODS: Forty-two patients presenting a non-metastatic castration-resistant prostate cancer after PADT were referred to our institution and underwent RT between June 2003 and July 2011. Biochemical failure (BF) after EBRT was defined according to Phoenix criteria (nadir + 2 ng/mL "at call"). Median RT dose was 78 Gy. RESULTS: Median duration of PADT was 54 months (range 10.2-181 months). Median follow-up after EBRT was 53 months. Twenty-one patients had BF after EBRT (median time 27.4 months): 13 presented with loco-regional and/or distant metastases, while in 8 patients, a PSA rise only was observed. Ten patients died of prostate cancer (and no patient died of causes other than prostate cancer). Five-year biochemical disease-free survival (bDFS), distant metastases-free survival (DMFS) and cancer-specific survival (CSS) were, respectively, 39.4, 60 and 65 %. On multivariate analysis, GS, nadir PSA (nPSA) and a pre-EBRT PSA ≤5 ng/mL significantly affected bDFS, while Gleason score (GS) and T stage significantly affected distant metastases onset. No factors affected CSS at multivariate analysis. CONCLUSIONS: EBRT may be a suitable therapeutic option, able to provide an excellent loco-regional control and to obtain a systemic disease control in up to 60 % of patients at 5 years, especially in patients presenting with lower Gleason score and T stage at diagnosis and lower pre-RT PSA and nPSA post-RT.