Headlines internationally have warned of an increased risk of cancer associated with taking angiotensin converting enzyme  (ACE) Inhibitor medications such as enalapril and lisinopril  ( commonly used to treat hypertension and protect against heart attack and stroke) .  Researchers in Canada published the results of a large cohort study in the British Medical Journal. Previous studies looking at ACE Inhibitors and lung cancer have had mixed results.

The study included almost a million patients who were prescribed blood pressure medication in 1995 the patients were followed through their records until December 2016. People who took ACE inhibitors were 14% more likely to develop lung cancer during the follow-up period than those who took angiotensin receptor blocker (ARB)s, such as candesartan. Both medications lower blood pressure, they target different proteins and can have different side-effects as a result

This 14% increase risk represents a very small increase in absolute risk in people getting cancer ( there were 1.2 lung cancers for every 1000 people per year in the ARB group and 1.6 cancers for every 1000 people per year the ACE inhibitor group). This increased risk is very small and outweighed by known risk factors for lung cancer such as smoking and occupational exposure to certain dusts and chemicals. 

How lung cancer and ACE Inhibitor medication is linked is not fully understood. One theory is that ACE Inhibitors lead to an increase in naturally occurring substance called bradykinin in the lung, which causes blood vessel dilation and this may be linked to cancer growth.

The researchers identified people who had taken ACE Inhibitors, ARBs, or other blood pressure drugs with at least one year of health records before and after their first prescription. They then calculated the number of people who developed lung cancer during the follow-up ( average 64 years) in the ACE inhibitor and the ARB group. There was no increased risk for people who had been taking ACE Inhibitors for up to five years, the risk increased the longer the medications were taken after this.

They identified as many confounding factors as possible,  such as age, smoking, weight, lung disease, use of other drugs, but possibly not all the health and lifestyle factors that could have differed between people taking the two drugs nor taken into account other differences such the increase in cough those on ACE Inhibitors experience and the possibility this group had cancer discovered due to an increase in chest X-rays ordered.

Untreated high blood pressure has been unequivocally linked to heart attack, stroke and death with the risk being far greater than any threat posed by the link between taking ACE Inhibitor medication and lung cancer.

Your GP is well-placed to discuss the relative risks and benefits of the medication and your health outcomes before ceasing ACE Inhibitors due to an increased risk in lung cancer.

Hicks BM, Filion KB, Yin H, et al. Angiotensin converting enzyme inhibitors and risk of lung cancer: population based cohort study. BMJ. Published online October 24

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