Use of photosensitising diuretics and risk of skin cancer: a population-based case-control study

Diuretics have photosensitising properties. However, little is known about how these diuretics affect the risk of skin cancers. In North Jutland County, Denmark, we investigated whether the use of photosensitising diuretics was associated with an increased risk for developing basal cell carcinoma (BCC), squamous cell carcinoma (SCC) and malignant melanoma (MM). From the cancer registry, we identified primary cases of BCC, SCC and MM during the period of 1989-2003. We selected four population controls for each case from the Danish Civil Registration System, matched on age and gender. Prescriptions for photosensitising diuretics before cancer diagnosis were ascertained in the county's Prescription Database. We used conditional logistic regression to compute incidence rate ratio (IRR), controlling for the chronic medical conditions and for the previous use of oral glucocorticoids. We found an increased risk of SCC (IRR of 1.79 (95% confidence interval (CI): 1.45-2.21)) and MM (IRR of 1.43 (95% CI: 1.09-1.88)) among users of combined amiloride and hydrochlorothiazide therapy. An increased risk of MM (IRR of 3.30 (95% CI: 1.34-8.10)) was found among users of indapamide. We found little associations with risk of BCC. Our findings provide evidence that the use of some photosensitising diuretics is associated with an increased risk for SCC and MM.