Hydrochlorothiazide Use and Risk of Skin Cancer: A Population-Based Retrospective Cohort Study

Purpose: Hydrochlorothiazide (HCTZ) exposure has been linked to increased skin cancer in Caucasian (white) populations, especially squamous cell carcinoma (SCC), but not basal cell carcinoma (BCC). This study aimed to evaluate and compare skin cancer risks associated with HCTZ- and other antihypertensives use. Methods: This retrospective cohort study utilized Taiwan's National Health Insurance Research Database. We identified patients aged 20 years and older, newly receiving antihypertensive medications between 2004 and 2015. We calculated the medication possession ratio (MPR) for the first 2 years of treatment to determine patient eligibility and treatment classification, whereby only patients with MPR above 80% were included. These were subsequently categorized by the type of antihypertensives they received, namely HCTZ, other thiazide diuretics, non-thiazide diuretics or non-diuretic antihypertensives. Cox proportional hazards model was used to evaluate skin cancer risks, and these were then classified as SCC or BCC. Results: Our study included 41 086, 27 402, 19 613, and 856 782 patients receiving HCTZ, other thiazide diuretics, non-thiazide diuretics, and non-diuretic antihypertensives, respectively. We found BCC risks were similar when comparing HCTZ with other thiazides (adjusted hazard ratio: 0.84; 95% CI: 0.54–1.33), non-thiazide diuretics (0.93; 0.51–1.67), and non-diuretic antihypertensives (0.91; 0.66–1.26). We observed a higher SCC risk in the HCTZ group, compared to other thiazides (1.24; 0.74–2.08), non-thiazide diuretics (1.32; 0.70–2.51), and non-diuretic antihypertensives (1.23; 0.87–1.73), although the confidence intervals (CIs) were wide and crossed the null. Conclusions: We concluded that skin cancer need not be of major concern to physicians when prescribing antihypertensives for an Asian population.