Blood pressure-lowering and risk of cancer: an individual participant-level data meta-analysis and mendelian randomisation studies

Abstract

Abstract Background The current body of randomised evidence concerning the effect of blood pressure lowering on the risk of cancer remains limited. Purpose We leveraged the strengths of both randomised controlled trials (RCTs) and genomic information to examine this question. Methods Individual-level data from 314,016 participants from 42 RCTs were pooled to investigate the effect of blood pressure lowering on the risk of cancer through one-stage individual participant data (IPD) meta-analysis. The primary outcome was incident cancer, defined as the first occurrence of any cancer diagnosed after randomisation. Pre-specified subgroup analyses were conducted to assess heterogeneity in effect by follow-up time and baseline age groups, sex, body mass index categories, smoking status and previous use of antihypertensive drugs. Secondary outcomes were cause-specific cancer death and site-specific cancer risk comprising breast, colorectal, kidney, lung, prostate, and skin. Cox proportional hazard regression, stratified by trials, were used for statistical analyses. For site-specific cancers, analyses were complemented with Mendelian randomisation analyses using naturally randomised genetic variants associated with blood pressure lowering, retrieved from genome-wide association studies involving participants of European ancestry. Results Over a median of 4 years (interquartile range 2), 17,954 participants in RCTs were diagnosed with cancer of any type and 4,878 participants were reported to have died with cancer as the cause of death. In the IPD meta-analysis that compared the treatment arm with the comparator, no associations were identified between reductions in either systolic or diastolic blood pressure and the risk of incident cancer (hazard ratios [HRs] per 5 mmHg reduction in systolic and per 3 mmHg diastolic blood pressure were 1.03 (95% confidence interval [CI] 0.99-1.06) and 1.03 [0.98-1.07], respectively). We also found no pattern of increasing or decreasing relative risk for incident cancer during the follow-up period, nor was there evidence of heterogeneity in treatment effects across baseline subgroups. No effect on the risk of cause-specific cancer death was identified for either systolic or diastolic blood pressure lowering. Considering site-specific cancers, we also found no evidence of effect, except for a possible link with lung cancer risk, with HRs of 1.17 [99.5% CI 1.02-1.32] for systolic blood pressure and 1.17 [99.5% CI 0.98-1.36] for diastolic blood pressure lowering. In Mendelian randomisation studies, no association was observed for genetically determined systolic and diastolic blood pressure and all the considered site-specific cancers, including overall lung cancer and its subtypes. Conclusion We found no consistent randomised evidence to suggest that blood pressure-lowering has a substantial effect, whether increasing or decreasing, on incident cancer, cause-specific cancer death, or selected site-specific cancers.