Cancer Risk of Angiotensin II Receptor Blocker Valsartan: A Population-based Study.

Nitrosamine contamination of generic valsartan was found in 2018. This study aimed to investigate whether long-term use of valsartan increases cancer risk. Patients prescribed valsartan or amlodipine (control group) from 1 January 1, 2003, to June 30, 2010, were identified using the Clinical Data Analysis and Reporting System of the Hong Kong Hospital Authority, a territory-wide database in Hong Kong. Patients previously diagnosed with cancer, prescribed both medications, taking the medication, or followed up for <1 year were excluded. Cancer incidence, adjusted for age, sex, and Charlson Comorbidity Index, was the primary outcome and was estimated using Poisson regression in R version 3.6.1. Among 5023 valsartan users and 3692 amlodipine users, 887 and 740 were diagnosed with cancers during median follow-up periods of 10.97 and 12.12 years, respectively. The adjusted incidence of cancer in valsartan and amlodipine users was 165.29 (95% confidence interval 154.76-175.53) and 180.12 (167.35-193.67) per 10,000 person-years, respectively. The cancer incidence rate ratio of valsartan relative to amlodipine was 0.94 (0.88-1.01). Adjusted incidence rate ratios of valsartan relative to amlodipine were significant for breast cancer (0.63, 0.46-0.86) only. Our findings do not suggest an increase in incidence of cancer with long-term valsartan use. The duration of follow-up of more than 10 years of the study provides the reassurance that an increase in cancer risk is unlikely. Further studies are needed to elucidate the long-term effect of valsartan use on the risk of specific types of cancer.