Under-registration of melanoma in Belgium: an analysis

The overall underestimation of incident cancer cases in the Belgian National Cancer Registry is estimated at about 20-25%, with a probable larger under-registration among males. Melanoma incidence is suspected to be underestimated even further because of the hospital-based reporting system of the National Cancer Registry. To investigate the suspected underestimation of melanoma in Belgium, the official data were compared with international data on melanoma incidence and the results of a melanoma registration programme launched in the province of East Flanders. The Eindhoven Cancer Registry, which covers a registration area near the Belgian border, was used as a reference to calculate the expected number of melanomas in East Flanders for 1995. The results indicate an ongoing under-registration of melanoma cases by the National Cancer Registry. Based on the Eindhoven Cancer Registry data, the under-registration in East Flanders is estimated at 43% for males and 36% for females. The East Flanders registration programme apparently obtains a better registration in females. This is mainly due to a higher registration in the younger age groups. In these groups a higher proportion of in situ melanomas and a thinner median Breslow thickness of the invasive melanomas is observed.