Breast cancer drug Herceptin increases heart damage risk, study says

TORONTO, April 20 (UPI) -- Although doctors already monitor older breast cancer patients for heart damage if their treatment includes the drug trastuzumab, researchers suggest all patients on the drug should be monitored based on the results of a recent study.

Researchers in Canada report in a study, published in the Journal of Clinical Oncology, that the drug significantly increased the risk for major cardiac events among all patients, regardless of age.

Trastuzumab, sold as Herceptin, is a cancer drug used for HER2-positive cancers, including those of the breast, stomach and esophagus. The drug already is known to carry risks for congestive heart failure, especially when used with a type of cancer drug called anthracyclines.

"Trastuzumab regimens for breast cancer have greatly improved survival of breast cancer patients," Dr. Douglas Lee, a senior core scientist in the Cardiovascular Research Program at the Institute for Clinical Evaluative Sciences, in a press release. "Although the absolute risk was higher in older patients, younger patients were also at significant risk of major cardiac events with cancer treatment regimens."

For the study, researchers reviewed medical records for 18,540 women treated between 2007 and 2012 with a median age of 54, 79 percent of whom were younger than 65, who were treated with either trastuzumab with nonanthracycline chemotherapy, anthracyclines followed by trastuzumab or chemotherapy without either drug.

Among women treated with anthracyclines followed by trastuzumab, 6.6 percent had a major cardiac event -- four times higher than patients receiving other types of chemotherapy. For patients treated with trastuzumab with nonanthracycline chemotherapy, 5.1 percent had a major cardiac incident, which is 1.76 times higher than the group treated with other chemotherapy.

The researchers said the study is eye-opening because the number of patients receiving trastuzumab was twice as large as the largest previous study they are aware of.

The fact that it shows cardiac event risk as significantly high among all groups of patients suggests that as effective as the drug is against cancer, doctors should monitor all patients for potential cardiac side effects, the researchers said.

"These results suggest the need for equal consideration of surveillance for breast cancer therapy-related cardiac dysfunction in younger patients who have until now been considered at lower risk for cardiotoxicity from these drugs," Lee said.