High melanoma risk in non-melanoma skin cancer patients under age 40: a large retrospective cohort study.

BACKGROUND: Patients with a history of non-melanoma skin cancer (NMSC) are at increased risk for other primary cancers, in particular for cutaneous melanoma. However rarely such studies are able to identify age-specific risks due to the lack of statistical power. The objective was to compare the risk of melanoma development within age groups in a large cohort of NMSC patients and in a control group of non-dermatological patients. METHODS: A retrospective linkage analysis was performed between records of hospitalizations and the occurrence of melanoma was compared within 10-year age group by computing the relative risk (RR) and modeled using multiple logistic regression. RESULTS: The linkage procedures identified 30,929 individuals with NMSC and 25,956 control patients. Overall, NMSC patients had RR for melanoma of 6.2 compared to controls. Patients with NMSC and less than 40 years of age have a RR of melanoma of 25.1 compared to controls. Our study is a retrospective analysis, and our ICD-9 codes do not distinguish between Basal Cell Carcinoma and Squamous Cell Carcinoma, nor between subtypes of melanoma. CONCLUSIONS: Our large study suggests that prevention of melanoma in NMSC patients is mandatory, especially for patients which develop a NMSC under 40 years of age.