June 14, 2010 -- A group of medications commonly used to treat high blood pressure, heart failure, and kidney damage caused by diabetes have been linked to a small increase in the risk of developing cancer, according to a study.
Angiotensin-receptor blockers (ARBs) work by blocking angiotensin II, a hormone that increases blood pressure.
A study published online in The Lancet Oncology states that although there are no major safety concerns associated with ARBs, a previous trial had reported a significantly increased risk of fatal cancers in patients receiving the ARB candesartan compared with a placebo.
Researchers from Case Western Reserve University School of Medicine in Cleveland examined data from previous trials of ARBs. They also looked at new cancer data in five trials involving 61,590 patients, common types of cancers (lung, prostate, breast) in another five trials of 68,402 patients, and cancer deaths in eight trials involving 93,515 patients.
Most of the patients in these trials (85.7%) had received the ARB telmisartan.
The researchers report that, overall, those who had taken ARBs had a significantly increased likelihood of new cancer diagnosis compared with patients in comparison groups (7.2% as opposed to 6%).
Among the solid-organ cancers examined, only the risk of lung cancer was significantly increased in patients taking ARBs compared with the comparison groups (0.9% as opposed to 0.7%).
Further Investigation Needed
The researchers say they did not find any evidence of a significant increase in death rates from cancer among those who had taken ARBs, although they caution that the short follow-up period in the trials makes that conclusion hard to judge.
Lead researcher Ilke Sipahi, MD, and colleagues write, “Given the limited data, it is not possible to draw conclusions about the exact risk of cancer associated with each ARB.”
They conclude that “the increased risk of new cancer occurrence is modest but significant. [However] the finding of a 1.2% increase in absolute cancer risk over an average of 4 years needs to be interpreted in view of the estimated 41% background lifetime cancer risk.”
Mike Rich, executive director of the U.K. charity the Blood Pressure Association, tells WebMD by email: "The increased risk identified in this study really is very modest, however it does bear more study. What is important to remember is that this kind of drug saves countless lives by allowing the good management of high blood pressure in people who may otherwise be at a greater risk of having a stroke or heart attack."
Martin Ledwick, head information nurse at Cancer Research UK, says in an emailed statement: “It’s important that we try to understand all the side effects of drugs so that people can make an informed choice about their treatment. At the moment there isn’t enough evidence to draw any firm conclusions about how blood pressure drugs might affect cancer risk and this will need further investigation.
“People shouldn’t stop taking these drugs on the basis of this research; if they’re concerned they should speak to their [primary care doctor].”