A new, long-term analysis of breast cancer patients treated with Herceptin (trastuzumab) and chemotherapy shows that the percentage of women who suffer heart failure due to treatment doesn't increase over time. What's more, many of them recover much of the heart function they initially lose because of the drug.

The findings, presented at the annual meeting of the American Society for Clinical Oncology, are good news for women who have been treated with Herceptin, experts said.

"We're encouraged that we found no increase in heart failure risks long-term," said study researcher Priya Rastogi, MD, assistant professor at the University of Pittsburgh School of Medicine and assistant director of medical affairs for the National Surgical Adjuvant Breast and Bowel Project (NSABP), which organized the study. "While we need to continue monitoring patients closely for late cardiac effects, this is reassuring news for women taking this drug."

Herceptin is a relatively new drug for breast cancer. It blocks receptors for a protein called HER2/neu, which is present in abnormally high amounts in about 20%-25% of breast tumors. These tumors tend to be more aggressive. A clinical trial organized by the NSABP showed that adding Herceptin to standard chemotherapy for women with these tumors cut recurrences in half and helped women live longer.

However, that study also showed that Herceptin can cause heart failure in some women. In the first 3 years of follow-up, 4.1% of women treated with Herceptin plus chemotherapy developed congestive heart failure, compared to 0.8% of women on standard chemotherapy alone.

At the cancer conference, Rastogi presented data from the 5-year follow-up of those patients. The incidence of heart failure was "essentially unchanged," she said. After 5 years, 3.8% of women treated with Herceptin and 0.9% of women on chemotherapy alone had developed congestive heart failure.

The new analysis also showed that many of the women who initially developed problems with heart function while on Herceptin seemed to get much of it back over time. Heart function even improved in some of the 3.8% of women classified as having congestive heart failure.

"It's reassuring for women who had an early cardiac event that the majority of them will have a recovery," Rastogi said.

Using information from the study, Rastogi and her colleagues pinpointed factors that make a woman more likely to develop heart failure if she uses Herceptin. Being 50 or older, having low heart function already, and using medication for high blood pressure all raise the risk.

The research team is developing a formula doctors can use to calculate an individual woman's risk using these criteria. The model could help doctors decide which Herceptin regimen to use, Rastogi said.

For instance, for women at very high risk of heart problems, doctors might use different chemotherapy drugs along with the Herceptin (the anthracyclines typically used are also known to cause heart problems), or give Herceptin on a different schedule to lower the risk to the heart.

Citation: " Five year update of cardiac dysfunction on NSABP B-31, a randomized trial of sequential doxorubicin/cyclophosphamide (AC) -->paclitaxel (T) vs. AC -->T with trastuzumab." Presented June 4, 2007 at the annual meeting of the American Society of Clinical Oncology. First author: Priya Rastogi. MD, University of Pittsburgh School of Medicine.