External beam radiation for the treatment of castration-resistant prostate cancer following primary hormonal therapy with androgen ablation: Analysis and outcome of 21 patients.

Patients who undergo early androgen-deprivation therapy for prostate cancer may eventually develop castration-resistant prostate cancer. However, no optimal treatment for non-metastasized castration-resistant prostate cancer has yet been established. In the present retrospective, single-institutional study, the radiotherapy (RT) outcomes were evaluated in patients who underwent androgen-deprivation therapy for non-metastatic prostate cancer and subsequently developed castration-resistant disease. Following a thorough chart review, the data of 21 patients with castration-resistant prostate cancer who were treated between 2000 and 2010 with external beam radiation therapy (EBRT) at a prostate radiation dose of >45 Gy were evaluated. Of the 21 patients, 16 (76%) developed biochemical recurrence after RT, with a mean time to biochemical recurrence of 17 months. A total of 18 patients succumbed to the disease during follow-up, with a mean survival of 3 years after RT. A radiation dose of >66 Gy was associated with a longer time to biochemical recurrence after RT (P=0.011) and a longer survival, compared with a dose of ≤66 Gy (P=0.028). The mean overall survival time after RT was 42 months and did not depend on the primary hormonal treatment. Prostate-specific survival time was negatively associated with the Gleason score at diagnosis. The prostate-specific antigen (PSA) concentration prior to RT was a prognostic factor for biochemical recurrence of prostate cancer after RT, as well as for prostate cancer-specific survival. Finally, the multivariate analysis revealed that age, PSA concentration prior to RT and a high Gleason score were independent prognostic factors for prostate cancer-specific survival. Overall, our study findings demonstrated that disease progression was common after EBRT for castration-resistant prostate cancer and that survival was limited. However, young patients and those with low-risk disease at the time of diagnosis may benefit from RT.