Optimal Duration of Androgen Deprivation in Combination with Radiation Therapy for Japanese Men with High-Risk Prostate Cancer

Abstract

Objectives: To evaluate the efficacy and toxicity of external beam radiation therapy (EBRT) combined with androgen deprivation therapy (ADT) for Japanese high-risk prostate cancer (PCa) patients in a single institution. Methods: Seventy-five high-risk PCa patients were treated by three-dimensional conformal radiotherapy of 70 Gy combined with neoadjuvant, concurrent and adjuvant ADT. Results: Median age was 72 (59–82) years. Median initial serum prostate-specific antigen (PSA) was 19.0 (4.7–200) ng/ml. Median duration of the entire ADT was 27 (8–63) months. Median follow-up after initiating ADT and after completing EBRT was 66 (41–105) and 59 (36–94) months, respectively. Five-year overall, clinical progression-free, and biochemical progression-free survival rates were 98.3, 97.2, and 87.4%; 2 (2.7%) cancer deaths, 3 (4.0%) clinical progressions, and 11 (14.7%) biochemical progressions. Multivariate analysis suggested a total duration of ADT shorter than 24 months as an independent risk factor of biochemical progression (p = 0.01). Grade 3 toxicities related to EBRT were observed: 1 patient with proctitis and rectal bleeding and 1 patient with rectal bleeding. Conclusions: It is suggested that 70 Gy EBRT combined with ADT confers disease-free survival benefit with tolerable adverse events for Japanese high-risk PCa patients. ADT of 24 months or longer might be recommended to minimize biochemical progression.