International mortality trends in prostate cancer

Prostate cancer is widely considered to be a form of cancer whose aetiology is poorly understood and which is becoming much more frequent in developed countries. All national time series of prostate cancer mortality data available in the World Health Organisation (WHO) mortality database were analysed in a systematic manner to investigate whether prostate cancer mortality was increasing and whether there were any striking similarities in the nature of any changes between countries. In particular, Age-Period-Cohort modelling was employed to establish and estimate the nature of any changes taking place in risk among successive generations of men: the method of Holford (Stat Meth Med Res 1991; 1:317-337) was employed. In all datasets the cohort-risk has remained constant in men born throughout this century. It is notable that the cohort relative risks for any cohort in any country are small and never exceed 1.5. While in many countries the all-ages mortality rate of prostate cancer appears to be continuing to increase, this is being driven by increasing rates among the oldest age groups which could be subject to the potential influences of improvements in diagnosis and death certification. Based on the results obtained from these statistical models, it is expected that overall prostate cancer mortality rates will soon begin to decline in many countries. The small fluctuations in mortality rates in more recent cohorts of men contrast with the large increases seen in the incidence of prostate cancer and support the concept of an artificial inflation of incidence rates and a changing stage distribution brought about initially by aggressive histopathological examination of prostatectomy specimens and latterly by the increasing use of prostate specific antigen (PSA) testing