Differences in prostate cancer grade, stage, and location in radical prostatectomy specimens from United States and Japan

Background: To compared prostate cancer at radical prostatectomy between men in the United States (US) and Japan in the modern era.

Methods: Three hundred seventy consecutive totally embedded RP cases (159 US; 211 Japan) from 2010 to 2012 were reviewed.

Results: US men were significantly younger (mean age 58.8 years) than Japanese men (mean age 64.6 years; P < 0.00001). Japanese patients presented with higher PSA levels (mean = 10.9 ng/ml) compared to US patients (mean = 5.8 ng/ml, P < 0.00001) and higher clinical stage (P = 0.003). Japanese tumors were: higher grade; larger; more advanced stage; with increased lymphovascular invasion; and more commonly TZ in location (P < 0.00001). In multivariate analysis, independent predictors of high tumor volume were PSA level, clinical stage, TZ location, Gleason grade, and country of origin (Japan). Independent predictors of TZ location were clinical stage, tumor volume, and country of origin (Japan).

Conclusion: A major factor for larger, higher grade and stage tumors in Japanese patients is the lower prevalence of screening for prostate cancer in Japan. Another contributing factor may be their TZ location, where they are not palpable until advanced and where they are difficult to sample on needle biopsy possibly leading to a delay in diagnosis. The finding of a difference in zonality of prostate cancer between US and Japanese cases is novel and may reflect differences in biology rather than different health care practice between the groups. If this data is confirmed, consideration should be given to TZ sampling as part of routine needle biopsies in Japanese men.