Breast cancer patients treated with trastuzumab chemotherapy are at an increased risk for heart failure and/or cardiomyopathy (HF/CM) compared to women not treated with chemotherapy, according to a study published in the Journal of the National Cancer Institute.

Breast cancer is one of the most common cancers found in the U.S., with over 232,000 new diagnoses reported in 2011.

Although trastuzumab has been heralded as a step forward in personalised oncology, concerns about safety, namely regarding risk of congestive heart failure, have emerged.

Previous studies have shown that women treated for breast cancer with trastuzumab or anthracycline-based chemotherapy, are at an increased risk for HF/CM, but those clinical trials excluded older women and those with comorbidities, making it difficult to generalise about the overall breast cancer patient population.

In order to determine the risk for HF/CM in women treated for breast cancer, Erin J. Aiello Bowles M.P.H., lead author from the Group Health Research Institute in Seattle, conducted a population-based, retrospective cohort study which looked at 12,500 women with a mean age of 60, who were diagnosed with invasive breast cancer between January 1999-December 2007.

They assessed risk of HF/CM associated with anthracycline alone, trastuzumab alone, anthracycline followed by trastuzumab, and other chemotherapy compared with no chemotherapy usage, and results were adjusted for age at diagnosis, stage, Cancer Research Network site, year of diagnosis, radiation therapy, and comorbidities.

One of the study’s aims was also to gauge the actual use of trastuzumab and anthracycline-based chemotherapy, and the researchers found that women receiving anthracycline, with or without trastuzumab, tended to be younger and without comorbidities. Women on trastuzumab alone tended to be older and have more comorbidities.

“These results suggest substantial individualization of adjuvant chemotherapy administration by age and comorbidity in community practice,” the authors write. Furthermore, “The overall risk of incident HF/CM was statistically significantly increased among women who used anthracycline alone compared with no chemotherapy, but the overall risk of HF/CM was even greater among women who used trastuzumab.”

They add that while the risk with anthracycline alone had been previously reported by other studies, the risk associated with anthracycline plus trastuzumab was greater than previously reported.

In an accompanying editorial, Ann M. Geiger, M.P.H., Ph.D., of the Division of Public Health Services at the Wake Forest School of Medicine in Salem, North Carolina writes that the results of the study adds to the evidence that anthracycline or trastuzumab increases the risk of HF/CM as a long-term effect, particularly in the case of trastuzumab, saying that the study, “justifies long-term surveillance for congestive heart failure in women who have received trastuzumab, as well as extended follow-up of women enrolled in trials.”

Geiger adds that the Bowles study, which was observational, also “illustrates how observational studies complement randomised controlled trials by capturing valuable information about treatment outcomes for the vast majority of women who are unable to access a trial.”

Source: JNCI