Study data published in Hypertension suggest that treatment with certain antihypertensive medications may reduce risk for colorectal cancer. In a large, retrospective cohort study, patients who underwent treatment with angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs) were found to be at lower risk for colorectal cancer over 3 years of follow-up. However, ACE inhibitors did not appear to affect colorectal cancer risk >3 years after cohort entry.

Data were abstracted from the Hong Kong Hospital Authority electronic database, which comprises demographic and clinical information for patients treated at 90% of primary, secondary, and tertiary healthcare centers in Hong Kong. Patients aged ≥40 years who had undergone colonoscopy between 2005 and 2013 were eligible for inclusion. Only patients with a negative colonoscopy — defined as no colorectal cancer or adenoma detected — were included. The primary outcome was diagnosis of colorectal cancer within 3 years of baseline colonoscopy. Patients who received a diagnosis of colorectal cancer <6 months after colonoscopy were excluded, as were patients with a history of colorectal cancer, inflammatory bowel disease, or colectomy. Exposure to ACE inhibitors and/or ARBs was defined as ≥180-day use within 5 years before the index colonoscopy. Cox proportional hazards model was used to assess the risk for colorectal cancer by medication exposure status with adjustment for date of index colonoscopy, sex, history of colonic polyps, polypectomy at index colonoscopy, smoking status, alcohol consumption, comorbidities, and concurrent medication use.

A total of 187,897 patients were included in analyses, for a total of 560,306 person-years of follow-up. Just over half (51.1%) of participants were women. Median age at index colonoscopy was 60.6 years (interquartile range [IQR], 52.3-71.9). Overall, 854 patients developed colorectal cancer within 3 years of initial colonoscopy. Median age at cancer diagnosis was 75.9 years (IQR, 65.5-83.8), with a median time lapse of 1.2 years (IQR, 0.8-1.9) since index colonoscopy. Overall, 30,856 patients had used ACE inhibitors/ARBs, among whom 169 (0.55%) developed colorectal cancer. ACE inhibitors and ARBs were associated with a lower risk of colorectal cancer within 3 years of index colonoscopy (hazard ratio [HR], 0.78; 95% CI, 0.64-0.96). A dose-response relationship was observed, with each added year of ACE inhibitor/ARB use associated with a 5% reduction in adjusted hazard ratio. However, ACE inhibitors/ARBs did not reduce risk for colorectal cancer that developed >3 years after the index colonoscopy (HR, 1.18; 95% CI, 0.88-1.57).

The investigators noted that family history of colorectal cancer could not be ascertained, which represents a limitation of the study. Additionally, true prevalence of smoking and alcohol use was likely underestimated due to the use of diagnostic codes rather than patient report. Even so, results suggest that ACE inhibitors and ARBs may have a protective effect against colorectal cancer. “Our study provided additional insights into the potential chemopreventive effects of ACE inhibitors/ARBs against [colorectal cancer] development, apart from their known cardiovascular and renal benefits,” the investigators wrote.

Disclosure: Several study authors declared affiliations with the pharmaceutical industry.

Please see the original reference for a full list of authors’ disclosures.

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