BACKGROUND : Use of angiotensin-converting enzyme inhibitors (ACEi) and angiotensin receptor blockers (ARB) has been postulated to reduce cancer risk by inhibition of tumor progression, vascularization, and metastasis. The renin-angiotensin system is upregulated in colorectal cancers; however, the association of ACEi and ARB use with colorectal cancer risk is not well understood.

METHODS : The study population was 142,812 Women's Health Initiative participants free of colorectal cancer who reported on ACEi and ARB use at baseline; 2,216 incident colorectal cancers were diagnosed during 10 years of follow-up. Cox regression models estimated adjusted hazard ratios (HR) and 95% confidence intervals (CI) for associations relative to non-use among normotensive women, untreated hypertensive women, and hypertensive women treated with other antihypertensive medications.

RESULTS : HRs among women who used any ACEi or ARB compared to non-use in the 3 referent groups ranged between 0.97 and 1.01. Findings were similar for increased ACEi/ARB duration and for medications examined as separate classes or individually.

CONCLUSIONS : In this large prospective study of women, no associations of ACEi or ARB use with colorectal cancer risk were observed.

IMPACT : Choice of drug in the large population of aging women who will be prescribed ACEi and ARB should be made without factoring in any benefit on colorectal cancer risk.