Cancer risk in patients with earlier diagnosis of cutaneous melanoma in situ.

We calculated the short-term and long-term risks of developing cancer among 3,766 patients with a diagnosis of cutaneous melanoma in situ in Sweden from 1958 to 1992. In total, 393 patients developed a primary cancer at any site compared with an expected number of 177 [standardized incidence ratio (SIR) = 2.2, 95% confidence interval (CI) = 2.0-2.4]. Patients below 60 years of age at diagnosis had the highest SIR (2.7, 95% CI = 2.3-3.2). The overall risks were similar between men and women. The highest risk was seen during the first year of follow-up, though the risk remained elevated also after 15 or more years of follow-up. For specific sites, the highest SIR was found for developing invasive cutaneous malignant melanoma (SIR = 22.2). The risk of subsequent primary non-melanoma skin cancer was elevated 8-fold in men and almost 7-fold in women. An elevated risk was also found for female breast cancer (SIR = 1.4). Especially among women, other sites with increased cancer risk (though not significant) were non-Hodgkin's lymphoma (SIR = 1.9), multiple myeloma (3.2) and cancers of the colon (1.6) and pancreas (1.6). In conclusion, patients with melanoma in situ run a generally increased risk of developing primary cancers, especially cutaneous malignant melanoma and non-melanoma skin cancer. The increased long-term risk of cancer after diagnosis of melanoma in situ may be due to continuing carcinogenic exposure or to intrinsic tumor susceptibility.