Epidemiology of extracutaneous melanoma in the Netherlands

Background: Reliable population-based incidence and survival data on extracutaneous melanoma (ECM) are sparse. Methods: Incidence data (1989-2006) from the Netherlands Cancer Registry were combined with vital status on January 1, 2008. Age-adjusted annual incidence rates were calculated by direct standardization, and the estimated annual percentage change was estimated to detect changing trends in incidence. Additionally, we carried out cohort-based relative survival analysis. Results: Ocular melanomas were the most common ECM subsite with European standardized incidence rates (ESR) of 10.7 and 8.2 per 1,000,000 person-years for males and females, respectively. In comparison, for cutaneous melanoma (CM), the ESRs for men and women were 122 and 155 per million person-years, respectively. No statistically significant trends in the incidence of ECM were detected, whereas an annual increase of 4.4% for men and 3.6% for women was detected in the incidence of CM. Relative survival for ECM was poor, but differed largely between anatomic subtypes ranging from a 5-year relative survival of 74% for ocular melanomas to 15% for certain subsites of mucosal melanomas. Conclusions: Of all ECM subsites, ocular melanomas had the highest incidence and the best survival. Mucosal melanomas were the second most frequent subsite of ECM. Five-year relative survival for all ECM subtypes was worse if compared with CM. No statistically significant trends in the incidence of (subsites of) ECM were determined. Impact: This study gives insight into the relative sizes of the different subgroups of ECM as well as an estimate of 5-year survival, which varies substantially by subsite.