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

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

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.

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.

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.