These results support the existence of shared risk factors for MCC and other cancers. Heightened awareness of the association between MCC and other cancers, particularly squamous cell carcinoma and chronic lymphocytic leukemia, may facilitate earlier clinical detection and treatment of MCC, thereby improving patient survival.

Background: Many commonly used medications, including both medications for long-term (daily) use and short-term use (treatment courses of finite duration), have photosensitizing properties. Whether use of these medications affects skin cancer risk, however, is unclear.Methods: Using a cohort of all Danish residents ≥15 years old in 1995 to 2006 (n = 4,761,749) and information from Danish national registers, we examined associations between use of photosensitizing medications and risk of basal cell carcinoma, cutaneous malignant melanoma, Merkel cell carcinoma, and squamous cell carcinoma.Results: Users of only 2 of 19 medications for long-term use (methyldopa and furosemide) had both a ≥20% increased risk of skin cancer (compared with nonusers) and an increase in risk with increasing duration of use; these effects were limited to basal cell carcinoma and squamous cell carcinoma, respectively. In contrast, 8 of 10 medications for short-term use were associated with both a ≥20% increased risk of skin cancer and an increase in risk with increasing use for at least one of the four cancers.Conclusion: We found little evidence of an increased risk of skin cancer among users of photosensitizing medications for long-term daily use, but could not rule out the possibility that users of some photosensitizing medications for short-term use may have an increased risk of skin cancer.Impact: Previous studies have been limited to specific medication types (e.g., antidiuretics). Our study examined the effect of a wide range of photosensitizing medications on skin cancer risk and suggests that future work should focus on photosensitizing medications for short-term use.

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