Prostatic cancer: some epidemiological features.

Prostatic cancer is a frequent tumour in old men. The disease is very common in North America, particularly among Blacks, and in Scandinavia, while it is currently rare in Asian countries. Both morbidity and mortality rates have increased in most areas in recent years, the rate of increase being greatest in populations where the risk has hitherto been low. "Latent" (microscopic) prostatic cancer is much commoner than overt clinical prostatic cancer and, in contrast to the latter, the prevalence is similar in a wide spectrum of countries and ethnic groups. Detection of these latent tumours is dependent on medical care variables. The relationships between tumor development, latency and progression are not understood. It may be useful to consider "latent" prostatic cancer as a separate entity in future classifications and epidemiological research. Hormonal, sexual, dietary, chemical and genetic factors have been implicated in the aetiology although the mechanisms by which they act and the relationships between these factors are not known. As a high fat diet has been found to increase risk in case-control studies, a plausible sequence of events would be a fat-induced change of hormone profile with increased uptake by the prostate of male sex hormones leading to carcinoma--as in the rat. The evidence is however by no means entirely consistent and should be explored further in studies of the US Black and White populations, populations with age-standardized incidence rates in the order of 100 and 50 per 100,000 per annum respectively. If it be accepted that the factors leading to latent carcinoma of prostate are evenly distributed throughout the world, then studies directed at uncovering the agents responsible for progression from latent to clinically invasive state could be rewarding. Such studies would need to be large, prospective in nature and would require a high frequency of autopsy of cohort members to ascertain whether the prostate was cancer free or not. Prevention is not feasible on the basis of current knowledge and further inquiry regarding the aetiopathogenesis of prostatic cancer is needed before preventive approaches can be envisaged.