Taking the Good With the Bad: Mitigating Heart Problems With Breast Cancer Medication

Herceptin has improved survival for women with HER2-positive breast cancer. Now, scientists are exploring ways to mitigate the heart problems the drug can cause.
When told by an oncologist that her breast cancer tested HER2-positive in June 2011, Margaret Isley didn’t quite understand the magnitude of such a diagnosis. And perhaps she partly wanted to keep it that way, for her own peace of mind. Normally, HER2 (human epidermal growth factor receptor 2) proteins play a key role in healthy breast cell development and repair. In about one in five patients with breast cancer, the cells make too many HER2 proteins, leading to uncontrolled growth and division. These HER2-positive breast cancers tend to be more aggressive, growing more quickly and spreading more rapidly than their HER2-negative counterparts.

Isley, a 65-year-old resident of Edmonton, Alberta, in Canada, found out about her HER2 status two months after an initial diagnosis of breast cancer. Her doctors broke the news to her, but also made it clear that she had a promising treatment option: Herceptin (trastuzumab), a monoclonal antibody that prevents the HER2 proteins from receiving growth signals.

“When my oncologist presented the whole HER2-positive information to me, he said it was fortunate that I didn’t have this before 2005, when Herceptin was first approved in Canada,” says Isley. “I’m thankful that the medical profession has progressed to such a level.”

At the same appointment, she decided to participate in a double-blind randomized trial headed by clinician scientist Edith Pituskin, Ph.D., of the University of Alberta, who described the risk of cardiac toxicity for patients treated with Herceptin and explained that she wanted to find a way to prevent this side effect.

As helpful as Herceptin is, it can cause decreases in the heart’s muscle function. While only 1 to 4 percent of patients experience symptoms from this, and while most patients recover, 10 to 15 percent may undergo a delay or halt in treatment due to this problem. Isley’s mother had died at 85 of an acute cardiac issue, and so the possibility of heart failure due to the drug remained a concern for her.

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