Hong Kong—Angiotensin converting enzyme (ACE) inhibitor or angiotensin II receptor blocker (ARB) medications are commonly prescribed for conditions such as heart failure, high blood pressure or heart disease. Now, a new study suggests those drugs might also be protective against colorectal cancer in some situations.

The research published in Hypertension, an American Heart Association journal, describes how ACE inhibitors and ARBs block angiotensin, a chemical that causes arteries to narrow.

“The roles of ACE inhibitors and ARBs on cancer development are controversial and, in some cases, study findings are conflicting. Results of previous studies have been limited by several factors including a small number of patients and data only on short-term follow-ups. Our results provide new insights on a potential role of these medications for colorectal cancer prevention,” explained study author Wai K. Leung, MD, clinical professor of medicine at the University of Hong Kong in Hong Kong. “This is the first study to show the potential beneficial effects of ACE inhibitors and ARBs on colorectal cancer development, based on a large group of patients who were colorectal cancer-free at the beginning of the study.”

Researchers sought to determine the association between the drugs’ use and colorectal-cancer risk after a negative baseline colonoscopy. The territory-wide retrospective cohort study recruited patients aged 40 years and older who had undergone colonoscopy between 2005 and 2013. Exclusion criteria included colorectal cancer detected within less than 6 months of index colonoscopy, prior colorectal cancer, inflammatory bowel disease, and prior colectomy.

Defined as the primary outcome was colorectal cancer diagnosed between 6 and 36 months after index colonoscopy. The study team categorized sites of colorectal cancer as proximal (proximal to splenic flexure) and distal cancer.

The study derived the adjusted hazard ratio of colorectal cancer with ACE inhibitor/angiotensin receptor blocker use (≥180-day use within 5 years before index colonoscopy) by propensity score regression adjustment of 23 covariates.

These included factors such as demographics, concurrent medication use, and endoscopy center’s performance.

Of 187,897 eligible patients, 30,856 (16.4%) were found to be ACE inhibitor/angiotensin receptor blocker users. Of those, 854 (0.45%) developed colorectal cancer between 6 and 36 months after index colonoscopy (proximal cancer: 147 [17.2%]).

Researchers report that ACE inhibitor/angiotensin receptor blocker use was associated with lower risk of colorectal cancer that developed less than 3 years after index colonoscopy (adjusted hazard ratio, 0.78; 95% CI, 0.64-0.96), but not colorectal cancer that developed more than 3 years later (adjusted hazard ratio, 1.18; 95% CI, 0.88-1.57). In fact, the authors write that each single-year increase in the use of the drug was associated with 5% reduction in adjusted hazard ratio risk, explaining, “ACE inhibitors/angiotensin receptor blocker were associated with a lower colorectal cancer risk in a duration-response manner.”

“While ACE-i and ARBs are taken by patients with high blood pressure, heart failure and kidney diseases, the reduction in colorectal cancer risk may be an additional factor for physicians to consider when choosing anti-hypertensive medications,” Dr. Leung said.

Noting that theirs was a retrospective study, the researchers say their results should be verified with a prospective randomized, controlled study.

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