Take-home message for physicians
Another expert emphasized the observational nature of both studies. Raymond Townsend, MD, director of the Hypertension Program and a professor of medicine at the Hospital of the University of Pennsylvania, Philadelphia, said: “First and foremost, these are observational studies and cannot make inference about causality; they can only show associations.”
He pointed out that, sometimes, associations are truly present, whereas at other times, there is bias or confounding that cannot be controlled for statistically because it is “unknown.” That said, the size of this latest study is a plus, and there is a reasonable follow-up period.
“The take-home [message] for practitioners is that there may be a benefit in keeping older people on ACE inhibitors on the likelihood of developing colorectal cancer if your last colonoscopy was negative,” Dr. Townsend, who was not involved in the study, said in an interview.
But there are some questions that remain unanswered regarding characteristics of the cohort, Dr. Townsend noted. “Who were the people having the colonoscopy in the first place? Were they a group at higher risk? Why were some on an ACE inhibitors/ARBs and many others not?”
There are other conclusions that clinicians can glean from this. “Make a choice of treatment for a patient based on your best estimate of what will lower their blood pressure and prevent hypertension-mediated organ damage,” said Dr. Townsend, who is also an American Heart Association volunteer expert. “Keep in mind that patients hear about these studies and read unreviewed blogs on the web and so have questions.”
He emphasized that it always comes back to two things. “One is that every treatment decision is inherently a risk-benefit scenario,” he said. “And second is that most of our patients are adults, and if they choose to not be treated for their hypertension despite our best advice and reasoning with them, relinquish control and let them proceed as they wish, offering to renegotiate in the future when and if they reconsider.”
Study details
In the latest study, Dr. Leung and colleagues conducted a retrospective cohort study and used data from an electronic health care database of the Hong Kong Hospital Authority. A total of 187,897 individuals aged 40 years and older had undergone colonoscopy between 2005 and 2013 with a negative result and were included in the analysis.
The study’s primary outcome was colorectal cancer that was diagnosed between 6 and 36 months after undergoing colonoscopy, and the median age at colonoscopy was 60.6 years. Within this population, 30,856 patients (16.4%) used ACE inhibitors/ARBs.
Between 6 months and 3 years after undergoing colonoscopy, 854 cases of colorectal cancer were diagnosed, with an incidence rate of 15.2 per 10,000 person-years. The median time between colonoscopy and diagnosis was 1.2 years.
ACE inhibitor/ARB users had a median duration of 3.3 years of use within the 5-year period before their colonoscopy. Within this group, there were 169 (0.55%) cases of colorectal cancer. On univariate analysis, the crude hazard ratio (HR) of colorectal cancer and ACE inhibitor/ARB use was 1.26 (P = .008), but on propensity score regression adjustment, the adjusted HR became 0.78.
The propensity score absolute reduction in risk for users was 3.2 per 10,000 person-years versus nonusers, and stratification by subsite showed an HR of 0.77 for distal cancers and 0.83 for proximal cancers.
In a subgroup analysis, the benefits of ACE inhibitors and ARBs were seen in patients aged 55 years or older (adjusted HR, 0.79) and in those with a history of colonic polyps (adjusted HR, 0.71).
The authors also assessed if there was an association between these medications and other types of cancer. On univariate analysis, usage was associated with an increased risk of lung and prostate cancer but lower risk of breast cancer. But after propensity score regression adjustment, the associations were no longer there.
The study was funded by the Health and Medical Research Fund of the Hong Kong SAR Government. Dr. Leung has received honorarium for attending advisory board meetings of AbbVie, Takeda, and Abbott Laboratories; coauthor Esther W. Chan has received funding support from Pfizer, Bristol-Myers Squibb, Bayer, Takeda, Janssen (a division of Johnson & Johnson); Research Grants Council of Hong Kong; Narcotics Division, Security Bureau; and the National Natural Science Foundation of China, all for work unrelated to the current study. None of the other authors have disclosed relevant financial relationships. Dr. Azoulay has disclosed no relevant financial relationships. Dr. Townsend is employed by Penn Medicine.
A version of this article originally appeared on Medscape.com.
