Radiation therapy and a number of commonly used chemotherapy drugs can impair heart function, says Anju Nohria, MD, a cardiologist who leads the cardio-oncology program at Dana-Farber/Brigham and Women’s Cancer Center (DF/BWCC). The drugs can also worsen heart conditions that patients had prior to their cancer treatment.
Chemotherapy drugs known as anthracyclines, including doxorubicin (Adriamycin), used in treating breast, lung, and ovarian cancer, and some leukemias and lymphomas, can damage heart muscles. Trastuzumab (Herceptin), a breast cancer drug, can also be toxic to the heart. Ibrutinib, a blood cancer drug, may cause atrial fibrillation, and there is a risk of high blood pressure from treatment with certain targeted drugs. The newer class of immunotherapy agents called checkpoint inhibitors can cause myocarditis, an inflammation of the heart muscle. These conditions may lead to heart failure, when the heart is too weak to supply the body with sufficient oxygen.
Recently, the American Society of Clinical Oncology (ASCO) issued guidelines to clarify best practices for preventing and monitoring heart problems in survivors of adult-onset cancers. These guidelines suggest avoiding cardiotoxic treatments, including those mentioned above, for patients with heart disease or cardiac risk factors, if alternatives can be substituted without compromising patient outcomes.
When alternatives can’t safely be used, oncologists are advised to take steps to minimize the heart’s exposure to certain drugs and to radiation. One strategy is to use lower doses of cancer drugs, in combination with medications to help protect the heart. Radiation therapy can also be modified to avoid radiating the whole chest in some cases. Another measure during radiation is for patients to take deep breaths and hold them, which keeps the heart out of the direct path of the radiation beam. Nevertheless, “you have to make sure the cancer is appropriately treated,” Nohria stresses.
With more people living longer following cancer treatment, survivors should be monitored for signs that their heart is not functioning normally as a result of treatment, Nohria says. Recent studies suggest that in most cases, damage from anthracycline chemotherapy drugs is likely to appear within the first post-treatment year. Therefore, cardiologists recommend heart function be tested with an echocardiogram before treatment starts and again one year following treatment.
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