BERKELEY, CA (UroToday.com) - Prostate cancer is an ideal disease to prevent or delay progression of because it is the second most common cancer in elderly men and the progression is generally gradual.
It is well known that the incidence of prostate cancer in Asian men is lower than that in Caucasians. In Asia, prostate-specific antigen (PSA) screening is currently under-utilized, however screening rates have been increasing in some Asian countries. Not surprisingly, regardless of lower rates of PSA screening in Japan, potential overtreatment for low grade tumor has already been observed. If PSA screening ratio rises, the number of patients diagnosed with low-risk cancer also rises, and consequently, the number of cancer interventions would also increase. These features clearly indicate that potential issues of overdiagnoses and overtreatment for low-risk prostate cancers seen in the US should also be considered in Asian countries.
Discussion of prostate cancer risk reduction by 5-alpha-reductase inhibitors has been limited to results of their use with Caucasian men. REDUCE was a 4-year international, multicenter, randomized, double-blind, placebo-controlled, parallel-group study with 42 participating countries. Our post-hoc analysis aimed to investigate whether the results for Asian subjects were in line with those of the overall population of primarily Caucasian men. Unfortunately the treatment differences did not reach statistical significance due to the small numbers of the Asian subpopulation. However, dutasteride seems to be effective for Asian men because of the consistent outcomes in the Asian subpopulation. First, similar trends in prostate cancer risk reduction were observed with less prostate cancer detected in dutasteride-treated men compared to placebo-treated men. Second, less tumor with low Gleason score was mainly observed in dutasteride-treated men. And finally, less detection of high-grade intraepithelial neoplasia (HG-PIN) or atypical small acinar proliferation (ASAP) was seen in the dutasteride group.
Additionally, our results provide some interesting insight into prostate cancer management in Asian counties. After 4 years, prostate cancer incidence in the placebo-treated men did not substantially differ among race. Japan was the only Asian country participating in the REDUCE study and approximately 40% of the Asian subpopulation were Japanese men. The remaining 60% were enrolled from non-Asian countries, mainly in the US. In other words, the majority of the Asian population seems to be Asian immigrants living in the Western countries. Therefore, it is natural that the cancer incidence in the placebo arm of the Asian subpopulation was near to that of the overall population. Rather, it is interesting that the incidence of Japanese men was also similar to that of the Asian subpopulation. Although we cannot reach a definitive conclusion from our results, Asian subjects who had the same levels of PSA might generally have a similar risk of developing prostate cancer compared with Caucasian.
In summary, the effects of dutasteride on reduction of the risk of developing future prostate cancer should be observed in the Asian population as well. Considering the recent increase of incidence and mortality of prostate cancer in Asian countries, our results could provide some valuable information for prostate cancer management in Asian men.
Hideyuki Akaza, MD as part of Beyond the Abstract on UroToday.com. This initiative offers a method of publishing for the professional urology community. Authors are given an opportunity to expand on the circumstances, limitations etc... of their research by referencing the published abstract.