BLADDER-CANCER INCIDENCE AND SURVIVAL IN THE SOUTH-EASTERN PART OF THE NETHERLANDS, 1975-1989

Trends in cancer occurrence and survival may reflect changing risks an d prognosis, respectively, but may also be caused by changes in detect ion, classification and registration. Changed classification of low-st age papillary carcinomas may have a material effect on observed trends in the occurrence of bladder cancer. We studied the effect of the imp lementation of the WHO grading system and the third edition of the TNM staging system on bladder cancer incidence in the south-eastern part of the Netherlands. Data on superficial and invasive bladder cancer in cidence between 1975 and 1989 were derived from the population-based E indhoven cancer registry. Data on survival of patients with stages I-I V bladder cancer were derived from the municipal population registers. Age-adjusted bladder cancer incidence per 100 000 person-years rose f rom 25.9 to 40.7 in males and from 3.1 to 8.5 in females. This increas ing trend was caused almost entirely by non-invasive pTa papillary car cinoma. A considerable shift was observed towards lower disease stages , which was less evident within the group of invasive tumours. The rel ative 5-year survival of patients with stages I-IV invasive bladder ca ncer was 59% in 1975-1977 and 70% in 1984-1986. After stratification b y stage, however, no striking improvement was observed in the prognosi s. We conclude that the increasing trend of bladder cancer occurrence in the Netherlands since 1975 has largely been caused by changed class ification systems and reporting procedures for pTa tumours (formerly c lassified as papillomas).