Hydrochlorothiazide use and risk of keratinocyte carcinoma and melanoma: A multisite population-based cohort study

The association between hydrochlorothiazide (HCTZ) and skin cancer remains controversial.

To determine whether HCTZ is associated with an increased risk of skin cancer compared with angiotensin-converting enzyme inhibitors and calcium channel blockers.

Two new-user, active comparator cohorts were assembled using 6 Canadian databases. Site-specific hazard ratios (HRs) with 95% CIs were estimated using standardized morbidity ratio weighted Cox proportional hazard models and pooled using random-effects meta-analysis.

HCTZ was not associated with an overall increased risk of keratinocyte carcinoma compared with angiotensin-converting enzyme inhibitors or calcium channel blockers, although increased risks were observed with longer durations (≥10 years; HR: 1.12; 95% CI: 1.03-1.21) and higher cumulative doses (≥100,000 mg; HR: 1.49; 95% CI: 1.27-1.76). For melanoma, there was no association with angiotensin-converting enzyme inhibitors, but a 32% increased risk with calcium channel blockers (crude incidence rates: 64.2 vs 58.4 per 100,000 person-years; HR: 1.32; 95% CI: 1.19-1.46; estimated number needed to harm at 5 years of follow-up: 1627 patients), with increased risks with longer durations and cumulative doses.

Residual confounding due to the observational design.

Increased risks of keratinocyte carcinoma and melanoma were observed with longer durations of use and higher cumulative doses of HCTZ.