Changes in the trends of initial treatment for newly diagnosed prostate cancer in Japan: a nationwide multi-institutional study.

Background: In previous large-scale studies conducted through 2010, androgen deprivation therapy (ADT) was the most common initial treatment for prostate cancer patients in Japan. However, recent advancements in treatment technologies have significantly affected the management of prostate cancer in Japan. This study analyzed the trends in initial treatments for prostate cancer based on two nationwide surveys.

Methods: Two Japan-wide multi-institutional surveys, J-CaP2010 and J-CaP2016, were conducted to enroll patients newly histologically diagnosed with prostate cancer in 2010 and 2016-18, respectively. Both surveys included age at diagnosis, initial PSA level, ISUP Grade Group, TNM classification, and initial treatment for prostate cancer.

Results: J-CaP2010 included data from 8192 patients across 140 institutions, whereas J-CaP2016 included data from 21 841 patients across 186 institutions. In J-CaP2016, the proportion of radical prostatectomy (RP) and radiation therapy (RT) in the initial treatment increased (from 32% to 36% and 21% to 26%, respectively), whereas the proportion of ADT decreased (from 40% to 29%) compared with those in J-CaP2010. The increase in RP or RT was noticeable in patients aged 75 years and older (from 20% to 38%) and those with high-risk localized cancer (from 58% to 74%) or locally advanced cancer (from 38% to 56%). The proportion of active surveillance or watchful waiting increased in patients with low-risk localized cancer (from 21% to 41%). The proportion of robot-assisted RP within all RPs and the proportion of intensity-modulated RT within all RTs increased remarkably (from 2.3% to 78% and 20% to 50%, respectively).

Conclusions: In Japan, RP and RT have increased as initial treatments for prostate cancer, whereas ADT has decreased. Consequently, RP has emerged as the most commonly selected initial treatment, replacing ADT.