More research needed on whether blood pressure drugs affect cancer risk

In collaboration with Adfero

A common class of blood pressure drugs called angiotensin-receptor blockers (ARBs) may be linked with a slightly increased risk of developing cancer, US scientists have found.

But Cancer Research UK emphasised that no firm conclusions can be drawn from their study and that people who take ARBs should not stop using their prescribed medicines without first talking to their GP.

ARBs are commonly used to treat people with high blood pressure, heart failure or diabetes-related kidney damage.

They work by blocking the receptor for a hormone called angiotensin II, which increases blood pressure.

Scientists at Case Western Reserve University School of Medicine in Cleveland, US, set out to examine the effect of ARBs on the development of new cancers.

The scientists analysed data contained in five trials on new cancers (involving 61,590 patients), five trials on common solid-organ cancers such as lung, prostate and breast cancer (68,402 patients) and eight trials on cancer deaths (93,515 patients).

Most of the patients involved in the trials - all of which were published before November 2009 - had received an ARB called telmisartan.

Researchers found that patients who took ARBs were more likely to be newly diagnosed with cancer than those who did not (7.2 per cent compared with six per cent).

Among solid cancers, the only one to be associated with an increased risk among ARB users was lung cancer.

The researchers also observed no significant increase in cancer deaths among ARB users, although they pointed out that the trials they looked at only had short follow-up periods.

They also noted that the studies had only looked at three ARBs (telmisartan, losartan and candesartan), meaning that their conclusions cannot be applied to ARBs in general.

Publishing their findings in the Lancet Oncology journal, they concluded: "Given the limited data, it is not possible to draw conclusions about the exact risk of cancer associated with each ARB. Our findings warrant further investigation."

Writing in an accompanying comment, Dr Steven Nissen from the Cleveland Clinic said that the findings raise important questions about the safety of ARBs.

He urged pharmaceutical companies to provide regulators with complete trial data so that the possible link between ARBs and cancer can be investigated properly.

"In the interim, we should use ARBs, particularly telmisartan, with greater caution," Dr Nissen advised, adding that they should be reserved for patients who are unable to take another class of blood pressure-lowering drug called angiotensin-converting enzyme (ACE) inhibitors.

Martin Ledwick, head information nurse at Cancer Research UK, commented: "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 GP."

References

Sipahi, I. (2010). Angiotensin-receptor blockade and risk of cancer: meta-analysis of randomised controlled trials The Lancet Oncology DOI: 10.1016/S1470-2045(10)70106-6