Incidence of invasive cancers following cutaneous malignant melanoma.

It has long been suggested that subjects diagnosed with cutaneous malignant melanoma (CMM) have an excess rate of subsequent neoplasms. To provide further quantitative information on the issue, we have considered 1,780 histologically confirmed CMM diagnosed between 1974 and 1994 by the Cancer Registries of the French-speaking Swiss Cantons of Vaud and Neuchatel (760,000 inhabitants) and followed up to the end of 1994 for the occurrence of a second primary. A total of 194 neoplasms was observed vs. 111.7 expected, corresponding to a standardized incidence ratio (SIR) of 1.7 [95% confidence interval (CI) 1.5-2.0]. When skin cancers were excluded, 87 subsequent neoplasms were observed vs. 84.9 expected (SIR 1.0). Significant excess rates were observed for basal cell (SIR 4.4), squamous cell (SIR 3.1) and melanoma (SIR 4.7) of the skin, as well as for prostatic cancer (SIR 2.1). The increased rates of subsequent skin cancer were somewhat larger in males, whereas all the SIRs were systematically greater below age 60. The SIRs of subsequent skin cancer remained above unity for 5 years or longer since diagnosis of CMM, in the absence of a clear pattern in trend with time since diagnosis. The cumulative incidence following CMM was 3% for CMM, 4% for squamous cell and 14% for basal cell carcinoma 20 years after diagnosis of CMM. Our results confirm that patients diagnosed with CMM have excess risks of subsequent melanoma and non-melanomatous skin neoplasms which justify focused prevention and surveillance of skin lesions in these patients. Subjects with CMM do not have any appreciable overall excess of non-skin neoplasms, even after long-term follow-up.