Long-tem use of certain widely prescribed blood pressure (BP) drugs may increase the risk of lung cancer, according to a study published Thursday in The BMJ.
Risk for individuals is still low, but could translate into large numbers of patients, said researchers led by Professor Laurent Azoulay from the McGill University in Canada.
Use of angiotensin converting enzyme inhibitor drugs (ACEIs) to lower BP is associated with an increased risk of lung cancer compared with use of another group of blood pressure drugs called angiotensin receptor blockers (ARBs), researchers said.
ACEIs are widely prescribed, so these small relative effects could translate into large absolute numbers of patients at risk for lung cancer, they said.
ACEIs are effective drugs used to treat high blood pressure (hypertension). Evidence suggests that ACEIs may increase the risk of lung cancer through the build-up of protein-like chemicals called bradykinin and substance P in the lung, said researchers.
These chemicals have been found on lung cancer tissue, and bradykinin may directly stimulate the growth of lung cancer.
However, previous observational studies examining this association are limited and report inconsistent results.
To better understand this possible association, Azoulay analysed UK primary care records for nearly one million patients who started taking a new antihypertensive drug between 1995 and 2015.
Patients were at least 18 years of age, with no previous cancer, and were followed up for an average of 6.4 years, during which time 7,952 cases of lung cancer were identified (a rate of 1.3 per 1,000 person years).
After taking account of factors that could potentially influence the findings, including age, sex, weight (BMI), smoking status, alcohol related disorders, and history of lung diseases, use of ACEIs was associated with an overall 14 per cent increased risk of lung cancer compared with ARBs.
Associations were evident after five years of use and increased with longer durations of use, particularly in patients who used ACEIs for more than 10 years (31 per cent increased risk).
Although the magnitudes of the observed estimates are modest, the researchers point out that ACEIs are one of the most widely prescribed drug classes, "so these small relative effects could translate into large absolute numbers of patients at risk."
They say these findings "should be replicated in other settings, particularly among patients exposed for longer durations."
This is an observational study, so no firm conclusions can be drawn about cause and effect, and the researchers cannot rule out the possibility that other unmeasured factors, such as socioeconomic differences, diet, and family history of lung cancer, may have affected the results.
However, this is the largest study to assess this specific association, and findings remained consistent after further analyses to test the strength of the results, researchers said.