WHICH cancer treatments may cause cardiac side effects?
Recently I had the privilege to chair a session at the annual convention of the Philippine Heart Association, discussing how cancer chemotherapy may weaken the heart muscle (cardiomyopathy) and cause rhythm disturbance (arrhythmia), even in previously normal hearts of young cancer patients.
Dr. Emil Canonigo, senior consultant at Cardinal Santos Memorial Hospital, and Dr. Maria Katrina Cruz Tan, head of the Cardio-Oncology section of St. Luke’s Medical Center, updated the audience—mostly heart specialists from all over the country—on how patients with heart failure, either due to cancer therapy or other causes, could be managed with drugs like candesartan. This drug is usually prescribed for people with high blood pressure and/or heart failure.
Ideally, cancer patients undergoing treatment, either by chemotherapy or radiation, should be evaluated by a heart specialist and monitored during the cancer treatment for side effects. Dr. Tan presented a clinical trial called the PRADA study, in which administering the drug candesartan helped prevent weakening of the heart muscles.
The different types of chemotherapy also have variable effects on the heart. Some anticancer drugs may have a dose-dependent irreversible damage on the heart, while other drugs may cause temporary side effects which resolve with discontinuation of treatment.
Some drugs may also increase the risks of heart attack. So, the cancer specialist should discuss these possible side effects with the patient before initiating treatment.
Cardiac side effects
Anticancer treatments that may cause cardiac side effects include:
• A class of drugs known as anthracyclines (doxorubicin, daunorubicin, others)
• Newer medications, such as trastuzumab and pertuzumab, which are drugs designed to attack certain cells (the HER2 protein) seen in some breast and other types of cancer
• Another class of drugs called taxanes, which can cause irregular heartbeat or arrhythmia. Symptoms include feeling light-headed or fainting, with or without palpitations.
Old anticancer drugs like fluorouracil can induce spasms of the coronary arteries that may lead to heart attack. The patient usually complains of chest pains or shortness of breath. However, this is easily reversible with prompt discontinuation of treatment.
Aside from the weakening of the heart muscles, these are some of the other potential side effects of cancer treatment on the heart:
• Stiffness of the heart muscles, preventing them from relaxing adequately during the resting phase (diastole) of the heart cycle
• Swelling or inflammation of the protective covering around the heart, called pericarditis. This could lead to scarring, called pericardial fibrosis.
• Thickened or leaky heart valves called valvular stenosis or insufficiency.
In cancer patients with preexisting heart disease, the oncologist or cancer specialist will have to choose an anticancer regimen that is least toxic to the heart.
During the Q&A of the session, Professor Nanette Wenger from the United States, who was a guest speaker in another session of the annual convention, said that although cancer chemotherapy affects primarily the rapidly dividing cells, normal cells like the heart cells can be “stunned,” similar to what happens during a heart attack.
This ventricular stunning may only be temporary, though, in the US experience.
It would indeed be unfortunate if cancer patients get cured of cancer but subsequently die due to heart failure, said Professor Wenger.