Under-registration of melanoma in Wales in 1998: use of the capture-recapture method to estimate the 'true' incidence.

Several studies have suggested that melanomas may be significantly under-recorded in cancer registries and that smaller, thinner, better prognosis lesions are the ones most likely to be missed. A systematic search of three independent sources of melanoma data in Wales for 1998 revealed a total of 406 histologically confirmed cases, of which only 194 were known to the cancer registry. Eighty-one per cent of the total cases were registered on a specialist melanoma register, compared with 48% on the cancer registry database. From the cancer registry data alone, the world age-standardized incidence rates (WASRs) were 4.3 and 5.8 per 100,000 for males and females, respectively, but these increased to 8.2 and 10.2 with the addition of histologically confirmed cases discovered from other sources. The capture-recapture method estimated the number of melanomas not ascertained by either means to be 140, resulting in a 'true' incidence of 546 cases for 1998 compared with just 194 cases from the cancer registry data alone. The 'true' WASRs are 11.2 and 13.4 per 100,000 for males and females, respectively, which are some of the highest in Europe. There was evidence to support the hypothesis that smaller, thinner melanomas are more likely to be recorded on a specialist melanoma register than on the cancer registry database.