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-re corded in cancer registries and that smaller, thinner, better prognosis les ions are the ones most likely to be missed. A systematic search of three in dependent sources of melanoma data in Wales for 1998 revealed a total of 40 6 histologically confirmed cases, of which only 194 were known to the cance r registry. Eighty-one per cent of the total cases were registered on a spe cialist melanoma register, compared with 48% on the cancer registry databas e. From the cancer registry data alone, the world age-standardized incidenc e rates (WASRs) were 4.3 and 5.8 per 100 000 for males and females, respect ively, but these increased to 8.2 and 10.2 with the addition of histologica lly confirmed cases discovered from other sources. The capture-recapture me thod estimated the number of melanomas not ascertained by either means to b e 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 tha t smaller, thinner melanomas are more likely to be recorded on a specialist melanoma register than on the cancer registry database. (C) 2001 Lippincot t Williams & Wilkins.