Subsequent primary cancers after basal-cell carcinoma: A nationwide study in Finland from 1953 to 1995.

The aim of this study was to investigate whether patients with basal-cell carcinoma (BCC) of the skin have an increased risk of developing other cancers. A total of 71,924 patients diagnosed with BCC between 1953 and 1995 were identified from the Finnish Cancer Registry. They were followed up for subsequent primary cancers from the date of the first BCC diagnosis to the end of 1995. Standardized incidence ratios (SIR) with 95% confidence intervals (CI) were calculated based on national rates. Altogether 11,042 subsequent primary cancers occurred among the study cohort during 625,000 person-years of follow-up. Risk increases were observed for non-melanoma skin cancer (SIR 3.79, 95% CI 3.59-4.00) and skin melanoma (SIR 2.34, 95% CI 2.08-2.61). The five other primary sites presenting the highest SIRs were salivary glands (SIR 3.30), lip (2. 19), small intestine (1.85), nose (1.73) and pharynx (1.71). Patients who were less than 40 years of age at the time of BCC diagnosis had a significantly higher relative risk for a subsequent new cancer than the older patients (ratio of the SIRs 1.29, 95% CI 1. 10-1.51). Time since BCC diagnosis did not materially influence the overall relative risk of subsequent cancers. Part of the increase in the risk of skin cancer is likely to be due to enhanced diagnostic activity after an initial diagnosis of BCC. However, the increases in the risk of several non-cutaneous cancers suggest a generalized carcinogenic role of some factors in the BCC pathogenic pathways.