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Published on November 10, 2020

You’re done with chemo, but could another problem emerge?

Chemo Heart

Cancer patients who rejoice at surviving chemotherapy and radiation may have something else lurking in their futures: heart issues.

Research, including a recent study of breast cancer survivors who took the chemo drug trastuzumab, known under the brand name Herceptin, showed that some of the powerful drugs that fight cancer can also lead to decreased heart function, high blood pressure or clotting. And radiation can damage arteries near the heart, leading to increased cardiac issues among breast cancer patients years after they have finished treatment, according to studies.

“I think the important thing would be for cancer survivors to realize they might be at higher risk of cardiac events in the long term,” said John C. Hostetter, MD, FACC, a cardiologist with Cape Cod Healthcare Cardiovascular Center in Falmouth. “I think the tendency is to focus on the cancer and do everything you can in that regard. People lose track of the fact that cardiovascular disease is still the number one killer of men and women.” 

The good news? More people are surviving cancer and there’s increasing awareness among cardiologists and oncologists of the long-term negative effects of treatment on the cardiovascular system, Dr. Hostetter said. And there are steps cancer survivors can take to help reduce their own cardiac risk.

What’s My Risk?

“Cancer survival has probably improved by 20 percent or so in the last 25 years with these new therapies,” Dr. Hostetter said. “The overall effect is positive. But, certainly, as people are living longer and there’s increasing numbers of cancer survivors, we’re seeing more cardiovascular effects.”

HER2 receptor blockers like trastuzumab, which are used to treat patients with HER2 positive tumors, is just one class of drug that can cause heart issues. One problem is that the drugs that attack cancer cells don’t always discriminate, creating issues in healthy cells, as well. The following are examples of other drugs that have been problematic for the heart, according to Dr. Hostetter and researchers:

  • Tyrosinase inhibitors, which help limit the blood supply to tumors, can raise blood pressure.
  • Tamoxifen, a hormone therapy for estrogen-positive breast cancer, can lead to a higher risk of blood clots.
  • Immune checkpoint inhibitors, used for several types of cancer, may lead to higher risk of myocarditis, or inflammation of the heart.
  • Imatinib, or Gleevec, used to fight leukemia, can lead to a drop in heart function.

Chemotherapy and radiation, particularly older, less-precise radiation therapy, can weaken the arteries near the heart, Dr. Hostetter said, as measured by ejection fraction, or how well your left ventricle is pumping, according to an echocardiogram. Typically, an ejection fraction number of 55 percent and above is considered healthy, Dr. Hostetter said.

What Can I Do?

People who are taking certain chemotherapy drugs that can affect the heart should be aware of possible side effects, such as swelling, shortness of breath, chest pain or sudden increase in blood pressure, Dr. Hostetter said. Any of those symptoms should trigger a referral to a cardiologist, he said. Patients who undergo combined chemotherapy and radiation can be at higher cardiovascular risk, as well.

The patients most at risk for treatment-related heart issues are those who are over 65 or who already have a co-condition - diabetes, for example - or a traditional cardiac risk factor like smoking. Patients already on cardiac drugs such as statins need to be vigilant about remembering to take them, he said.

And, cancer survivors need to pay attention to the common healthy-heart guidelines for diet and moderate exercise, he said.

“First of all, it seems that people who have better fitness and more regular exercise actually have a lower risk of certain cancers,” he said. “Then there’s data that patients who exercise have improved survival when they have cancer, although we don’t know exactly how that works.”

His advice translates to at least 30 minutes of aerobic exercise at least three times a week, and possibly additional strength training with weights twice a week. Studies have seen as much as a 30 percent increase in survival rates among cancer patients who exercise, he said.

“We don’t know why that is. It might be that exercise reduces inflammation. It might lower insulin levels. It certainly limits obesity and all the negative effects that come with that. In addition, it gives people more energy, less fatigue, better balance and even mental health.”

Dr. Hostetter is optimistic that early awareness of cardiac risks associated with cancer treatment will pay off for patients.

“There’s always something that when you treat one thing, there’s a risk down the road,” he said. “But cancer treatment is definitely a risk worth taking when you look at the short vs. the long term. Oncologists and cardiologists and patients will do better if we can at least be aware of the risks and recognize them earlier.”