Blood pressure medications are used for the treatment of high blood pressure and are one of the most commonly prescribed drugs in the world. This group of drugs includes hydrochlorothiazide, a thiazide diuretic. This drug helps patients lower their blood pressure but may make their skin more sensitive to the sun. Recently, there have been some concerns that patients using hydrochlorothiazide may be at a higher risk of skin cancer. To address this concern, we will conduct a large study using the Clinical Practice Research Datalink to examine whether patients using hydrochlorothiazide are at a higher risk of melanoma and non-melanoma skin cancer. Because skin cancer is the most common cancer in the UK, results from this study will provide important information on the long-term safety of these drugs.
Antihypertensive drugs are one of the most commonly prescribed drugs worldwide, with thiazide diuretics accounting for nearly 30% of these prescriptions. Hydrochlorothiazide is a type of thiazide diuretics with photosensitizing properties. Recently, some observational studies have reported associations with melanoma and non-melanoma skin cancer. This possible association however warrants further investigation. This is particularly important given that skin cancer has the highest incidence among all cancers. To address this question, we will assemble a cohort of approximately 200,000 patients newly treated with either hydrochlorothiazide or other thiazide diuretics between January 1, 1988 and March 31, 2018, with follow-up until March 31, 2019. Cox proportional hazard models will be used to estimate hazard ratios with 95% confidence intervals of melanoma and non-melanoma skin cancer comparing hydrochlorothiazide with other thiazide diuretics using propensity score matching and fine stratification. Secondary analyses will assess whether the risk of those cancers varies according to age, sex, and immunosuppressive status.
We will identify all incident melanoma and non-melanoma skin cancer events recorded in the CPRD (identified based on Read codes; see Table A1 in Appendix). Melanoma skin cancer includes 4 main types: superficial spreading melanoma, nodular melanoma, lentigo maligna melanoma, and acral lentiginous melanoma. Non-melanoma skin cancer includes basal cell carcinoma (BCC) and squamous cell carcinoma (SCC). Diagnoses of melanoma skin cancer in the CPRD have been previously validated, with a sensitivity of 77% for melanomas when compared with diagnoses in the UK National Cancer Data Repository.1,2 The CPRD has also been shown to capture more non-melanoma cases that are missed by other data sources.
Samy Suissa - Chief Investigator - Sir Mortimer B Davis Jewish General Hospital
Samy Suissa - Corresponding Applicant - Sir Mortimer B Davis Jewish General Hospital
Anton Pottegård - Collaborator - University Of Southern Denmark
Hui Yin - Collaborator - Sir Mortimer B Davis Jewish General Hospital
Julie Rouette - Collaborator - McGill University
Krishnarajah Nirantharakumar - Collaborator - University of Birmingham
Laurent Azoulay - Collaborator - McGill University