[Problems in mass screening program for prostatic diseases].

We developed transrectal ultrasonotomography for practical use in 1967 and started a model trial mass screening program for prostatic diseases with the method in 1975. A mobile unit "Dolphin" for mass screening, in which two sets of special chair-type scanner for the method was loaded, was developed successfully in 1980. Up to March, 1983, 2394 males over the age of 55 were submitted to the primary study. Among them, 12 cases (0.5%) of prostatic cancer (PC) and 755 cases (31.5%) of benign prostatic hypertrophy (BPH) were finally detected in the secondary study. Thus the prevalence of BPH was significant and even the detection rate of PC was still remarkably higher than that in mass screening for other malignancies. The diagnostic accuracy in transrectal ultrasonotomography in PC was calculated from the results of patients visiting our out-patient clinic during 7 years until March, 1983. The sensitivity was 96.5% and the specificity was 84.6%. On the other hand, the sensitivity of digital examination in the same series was 80.7%. We concluded from this study that the efficacy of digital examination was thought to be insufficient for the screening of PC. The cost-benefit balance in our mass screening system was estimated from the above mentioned results. We needed yen 2,000,000 to find out each case of early PC in the system. In our clinic, patients with early PC paid yen 2,000,000 in average for treatments including radical surgery and were cured. On the contrary, patients with advanced PC paid yen 5,000,000 approximately yen 8,000,000 and died eventually. The minimum difference of treatment fee between early and advanced PC was yen 3,000,000, accordingly. Since the cost of detecting each early PC in mass screening was yen 2,000,000, we are contributing approximately yen 1,000,000 to the national finance on each time when we pick up one case of early PC. This doesn't include benefits from detecting BPH and from life prolongation. Thus the balance seems to be sufficiently positive. In conclusion, a mass screening program for prostatic diseases is promising because it can detect the diseases accurately by transrectal ultrasonotomography with a good cost-benefit balance. The only remaining problem is how to transfer this to national political measures.