Findings from a prostate cancer screening program in a Japanese population.

Although Asia has a very low incidence of prostate cancer in comparison with other Asian countries, Japan has one of the highest incidence (30.4 per 100 000) and mortality rates (5 per 100 000) from prostate cancer, according to the 2012 GLOBOCAN estimates.1 Kitagawa et al.2 conducted a retrospective analysis of the population-based trends of prostate-specific antigen (PSA) screening conducted in men, between the ages of 54 and 69 years in Kanazawa city, which comprises of about a third of the Japanese population. In this annual screening program, they demonstrated a decreasing trend in the median serum PSA levels in men diagnosed with prostate cancer, when comparing the 5 year periods of 2000–2005 and 2006–2011, with a corresponding increase in low stage disease (T1c). However, no changes in PSA levels were detected in men without prostate cancer during these 5 years periods.

Screening for prostate cancer remains controversial due to overdiagnosis, harms associated with over treatment and no conclusive benefit in mortality.34 Kitagawa et al.2 demonstrated an increase in detection of T1c prostate cancers from 2006 to 2011, but there was no increase in lower grade disease (Gleason 6). Although it is possible that some low volume prostate cancers may have been missed by the use of a 6–12 core biopsy, and that the use of template biopsies and multi-parametric magnetic resonance imaging may have increased the yield of prostate cancer, these are not always feasible due to limited resources in most countries. As mortality rates were not available for this cohort of men, it is difficult to ascertain if there was any over detection of low grade cancers. Although statistically not significant, the study findings further demonstrated a slightly higher proportion of Gleason ≥7 disease detected during the latter 5 year period of the study. Changes in mortality/incidence ratios may have also provided further clues of over diagnosis and demonstrated any effects of increased Gleason ≥7 prostate cancers detected in the latter 5 year period.

A remarkable finding in this study is that the age-adjusted “cut-off” PSA levels in Japanese men in this cohort, was lower than the PSA levels in European and Middle-Eastern men, but appeared to be similar to that of Chinese and Korean men. Studies have previously demonstrated an increased incidence of prostate cancer in Asian-American men compared with men living in Asia, thought to be attributed to environmental factors.5 While, Kitagawa et al.2 acknowledge that factors such as body mass and weight (not accounted for) could have affected PSA levels in their study, they suggest that changes in diet and lifestyle may affect serum PSA levels in middle-aged men, which could help explain the differences in prostate cancer incidence between the native and migratory Asian men. Thus, these regional variations in PSA levels could play a role in determining region-specific “cut-off” levels of PSA, in addition to the age-specific PSA levels in different populations. However, further studies are needed to validate this noteworthy finding.

Despite the inherent limitations of a retrospective population-based study, Kitagawa et al.2 demonstrates some interesting features in the PSA screening program in a Japanese population, adding to the existing body of literature on population-based screening for prostate cancer.

COMPETING INTERESTS

The author declares no competing interests.