Editorial Comment from Dr Izumi to Clinical outcomes of prostate cancer patients in Yokosuka City, Japan: A comparative study between cases detected by prostate-specific antigen-based screening in Yokosuka and those detected by other means.

Abstract

Two large-scale studies published in 2009, one from the USA (Prostate, Lung, Colorectal and Ovarian Screening Trial)1 and one from Europe (European Randomized Study of Screening for Prostate Cancer Trial), evaluated the effect of prostate-specific antigen (PSA)-based prostate cancer screening (PSA screening) on prostate cancer mortality and reported contradictory findings. Patient mortality in the control group of the Prostate, Lung, Colorectal and Ovarian study could have been underestimated as a result of some controls undergoing PSA examinations before the study. Thus, this patient subset might essentially bridge the mortality gap between PSA screening and control groups. Even though several additional large studies have shown definite survival benefits with PSA screening, PSA screening is not recommended for prostate cancer detection in asymptomatic men in the USA. Because the mortality rate associated with prostate cancer in Japan has been lower than that in Western countries, the prevalence of PSA screening in Japan has remained low, which has hindered productive countermeasures against the current increase in deaths in Japan as a result of prostate cancer. In 2009, it was reported that 25% of patients with prostate cancer in Japan had PSA >100 ng/mL, whereas such high levels were relatively rare in the USA.2 In Western countries, it remains to be established whether PSA screening has clinical benefit and leads to improved patient survival. Because the ethnic, social and economical backgrounds of Japanese patients with prostate cancer are totally different from those of patients in the Western countries, and prostate cancer incidence and mortality are rapidly increasing, the potential beneficial impact of PSA screening on prostate cancer mortality should be precisely evaluated in Japan as well. Accumulating “real world” data from populations will help clinicians/urologists to understand the potential positive impact of PSA screening. In a study by Sakai et al., more than 1500 prostate cancer patients with and without PSA screening were enrolled and observed for 55 months.3 It was found that both prostate cancer-specific and overall survival were significantly higher in the PSA screening group than those in the non-PSA screening group. These results are consistent with previous findings, showing that patients diagnosed by PSA screening had a significantly higher probability of non-recurrence than patients diagnosed by non-PSA screening.4 Multivariate analysis showed that a Gleason score ≥8 was independently associated with both prostate cancer-specific and overall survival. Compared with the PSA screening patients, because the non-PSA screening patients had worse Gleason scores and were in higher risk categories, delayed diagnosis could logically have led to worse Gleason scores. However, the age at the time of diagnosis also significantly differed for PSA and non-PSA screening patients. PSA screening patients were on an average 2 years younger than non-PSA screening patients, possibly resulting in a lead-time bias that might explain the differences in the prostate cancer-specific and overall survival times between these groups. A prospective randomized study with a large sample size could clarify the effect of PSA screening on prostate cancer mortality with less bias. The results of the ongoing Japanese Prospective Cohort Study of Screening for Prostate Cancer,5 which is a cluster prospective cohort study that was initiated in 2002 to assess the effectiveness of PSA screening using mortality rate as the primary end-point, are a long time in coming. None declared.