Second primary cancers in patients with squamous cell carcinoma of the skin: A population-based study in Sweden

We studied second primary cancer among 25,947 patients diagnosed with squam ous cell carcinoma of the skin (SCC) in Sweden between 1958 and 1992, In to tal, 5,706 patients developed a second primary cancer at any site, compared with an expected number of 2,651 [standardized incidence ratio (SIR) = 2.1 5; 95% confidence interval (CI) = 2.10-2.21], Men below 60 years of age at diagnosis of SCC had higher SIR (2.5; CI = 2.2-2.8) with the highest risk d uring the first year of follow-up (SIR = 9.2; CI = 6.9-12.2). If second pri mary SCC was excluded, the SIR was reduced to 1.30 (CI = 1.25-1.34); the re lationships by sex, age and time since diagnosis remained similar. For skin cancer, the SIR for second SCC was markedly elevated (SIR = 15.6) and the risk of malignant melanoma was elevated 3-fold. Significantly increased ris ks were found for most second cancers in squamous cell epithelium: lip (SIR = 5,2), respiratory organs (SIR = 1.7), esophagus (SIR = 1,5), cervix uter i (SIR = 2,2), and vulva including vagina (SIR = 2.3), There was a generall y increased risk of almost 2-fold for second cancer in hematopoietic or lym phoproliferative tissues. Slightly increased rates (SIR = 1.0-1.5) were see n for second tumors in digestive tissues. Finally, a high SIR (SIR = 5.5) w as observed for second primary cancer in salivary glands. In conclusion, pa tients with SCC are at increased risk to develop new primary cancer, especi ally in skin, squamous cell epithelial and tobacco-related tissues, Common risk factors among the tumor types might explain our findings, however, an intrinsic susceptibility among SCC patients to develop cancer is also possi ble. (C) 1999 Wiley-Liss, Inc.