Recent trends in the initial therapy for newly diagnosed prostate cancer in Japan.

Objective: The objective of the present study was to investigate the trends over time in the initial treatment of prostate cancer in Japan.

Methods: A total of 8291 patients with newly diagnosed prostate cancer whose treatment started in 2010 were registered in a multi-institutional observational study undertaken nationwide across Japan by the Japan Prostate Cancer Study Group. Each patient's background characteristics and initial treatment were recorded.

Results: The median age at diagnosis was 71 years. The proportion of T1c disease was 40.5% and that of M1 disease was 10.4%. The prostate-specific antigen level was <10 ng/ml in 52.0% of the patients. High-, intermediate- and low-risk patients as determined by D'Amico's classification system made up 19.3, 29.8 and 25.9% of the cases, respectively. The initial treatment was androgen depletion therapy in 40.2%, radical prostatectomy in 32.0% (17.3% of these involved laparoscopic prostatectomy), radiation in 21.0% (46.4% of these involved brachytherapy). In cases of organ-confined disease, radical prostatectomy was selected in 39.5%, androgen depletion therapy in 28.0% and radiation in 23.9%. In D'Amico's low-risk group, the proportion treated with radiation was nearly equal to that treated with radical prostatectomy (30.2 and 32.7%, respectively); 73.2% of the radiation treatments involved brachytherapy.

Conclusion: Compared with previous Japanese studies, radiation use was increased by ∼10%. This increased proportion of radiation use was a typical trend in initial therapy for newly diagnosed prostate cancer cases in Japan. Although androgen depletion therapy use was decreased, it was selected in a high proportion of the patients irrespective of the disease stage.