PATIENTS are at greater risk of heart damage from the drug Herceptin than had been thought, with a quarter of those prescribed it for late-stage breast cancer suffering from cardiac complications, research suggests.

A study by American scientists shows that 28 per cent of patients with advanced breast cancer who are taking Herceptin suffered heart problems linked to muscle damage.

However, the authors said that the risk was acceptable and that the majority of the heart damage could be reversed with treatment. The drug, now licensed in the UK for early and advanced stages of the disease, was known to weaken the heart muscle and is, therefore, not recommended for those with heart trouble.

The National Institute for Health and Clinical Excellence (NICE) said in June, when approving the drug for early-stage use, that heart function must be assessed beforehand.

It also said that the drug should not be given to those at risk of heart failure and that patients should undergo regular assessments.

Previous research has shown that chemotherapy drugs, which are toxins, can cause damage that leads to cardiac complications. As a result of that damage, the heart is unable to pump enough blood to supply the body with essential oxygen and nutrients.

The latest research — the first analysis of Herceptin in advanced cancer cases outside clinical trials — showed that 49 of 173 patients who had used the drug for at least a year had experienced cardiac events.

The authors of the paper, published in the Journal of Clinical Oncology, emphasised that while heart muscle damage may be an issue for patients taking Herceptin for early-stage disease, the results of the study could not be applied directly.

Herceptin, also known as trastuzumab, was approved for use in 1998 for women whose advanced breast cancer is HER2-positive. About 30 per cent of metastatic breast cancer cells produce an excess amount of the HER2 growth protein on their surface, which makes the cancer more aggressive. Herceptin blocks this action, inhibiting tumour growth.

Other clinical trials testing Herceptin in combination with chemotherapy have found that between 10 and 26 per cent of patients experienced cardiac toxicity, depending on the treatment protocol.

Francisco Esteva, a professor in the Department of Breast Medical Oncology at the University of Texas, said that the latest findings offered an important insight into longer-term use of Herceptin. “The drug substantially prolongs survival, and while we found substantial cardiac toxicity, we also discovered that this side effect can be successfully treated, which was not clearly known before this study,” he said. “If the cardiac side effects of Herceptin treatment can be managed, the drug is safe to use.”

In the study 46 patients experienced cardiac toxicity “potentially associated with heart failure” and there was one heart-related death. All but three patients improved their cardiac function by discontinuing Herceptin and using treatments such as beta-blockers.

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