Potential overtreatment among men aged 80 years and older with localized prostate cancer in Japan.

Despite treatment guidelines recommending observation for men with low-risk prostate cancer with life expectancy <10 years, a majority of elderly patients choose active treatment, which may result in overtreatment. Given the growing burden of prostate cancer among men aged ≥80 years (super-elderly men), accumulation of survival data for evaluation of overtreatment among super-elderly patients is imperative. Here, we report results of a population-based cohort study to clarify potential overtreatment of super-elderly men with localized prostate cancer. We used cancer registry data from the Monitoring of Cancer Incidence in Japan project, which covers 47% of the Japanese population. The subjects were men diagnosed with prostate cancer between 2006 and 2008. Follow-up period was 5 years. We calculated 5-year relative survival rates among the active treatment and observation groups after imputation for missing values. Of the 48 782 patients with prostate cancer included in the analysis, 15.1% were super-elderly men. The 5-year relative survival rates of super-elderly men with localized cancer were 105.9% and 104.1% among the active treatment and observation groups, respectively. This excellent relative survival rate in the observation group remained consistent even after stratification by tumor grade. Of the 2963 super-elderly men with localized cancer, 252 (8.5%) with curative treatment and 1476 (49.8%) with hormone therapy were assumed to have been overtreated. The proportion of overtreatment was estimated to reach 80% after imputation. These specific survival data in super-elderly men in the observation group can be useful in shared decision-making for these patients and may lead to a reduction in overtreatment.