Heart disease and cancer are the top two causes of death in the U.S., according to the Centers for Disease Control and prevention. But cancer survivors may understand that many years after they are used, lifesaving cancer treatments—including chemotherapy and radiation therapy—can become a central issue in heart disease and, possibly, fatal heart attacks. Apart from a second cancer, heart disease is the main cause of lifetime illness and death in cancer survivors.

The good news is that with newer, innovative therapies, cancer patients are living longer. According to the American Cancer Society, there are approximately 17 million cancer survivors in the U.S. as of January 2019. This statistic means 5 percent of the nation’s population (or one in 20 people) have survived cancer. The number is expected to rise to about 30 million  by January 2030.

The bad news is that up to 50 percent will show some degree of heart dysfunction, or increased risk of a heart problem, within 20 years of treatment. Five percent will develop heart failure, and 40 percent will experience heart rhythm problems. The risk of death because of heart disease is eight times higher in cancer survivors as compared with the general population.

As a practicing cardio-oncologist, who takes care of cancer patients with heart disease, and director of the cardio-oncology program at Rush University Medical Center, I see heart disease risk in cancer patients and survivors as a health concern. Cardio-oncology is a newer and developing cardiac specialty that studies and manages these issues.

Researchers have found that in twins, an individual twin who had cancer and went through treatment has a higher risk of developing heart disease, as compared with his tor her sibling—almost as high for the cancer survivor as that same person’s risk of developing a second cancer.

The occurrence of heart disease caused by cancer treatment is possible because heart cells are very active. A person with an average pulse of 80 beats per minute has 115,200  per day and more than 42 million per year.

Obviously, no one could live without a heart, which pumps blood to all the other organs (including itself) to keep them working. To do this, the activities in the heart cells have to be very organized.

So anything that disturbs this orderliness—such as chemotherapy, radiation therapy, other heavy drugs or diseases—could lead to a heart not working properly in many ways. And that condition could then, in turn, lead to heart issues, including heart failure, attacks or rhythm problems, disease of the heart valves, hypertension or strokes.

Undoubtedly, it is necessary for patients to receive treatment to help them survive their cancer. Researchers have come a long way since the 1930s, when they began to formally use modern radiation therapy to treat cancer, and the 1950s, when they first employed chemotherapy to treat and cure it. Today immunotherapy is available that allows the body’s own immune system to target and kill cancer cells. This innovation has enabled patients who have cancers that would have been a death sentence in the past to live longer.

Yet it is very important for cancer patients to be educated on the risks to their heart after cancer treatments so they can work with their doctors to live heart healthy lives as cancer survivors. They need to know what to watch out for so any heart disease risk developed during treatment can be managed before it becomes a problem.

As cancer patients live longer, it is the duty of physicians within relevant specialties to learn more about survivors and how best to manage and treat them to help them have a good quality of life. Knowing more about the connections between cancer treatment and the heart in order to identify and arrest any future heart problems before they happen is crucial.

I believe we are obligated not only to educate our patients but also other physicians around us—especially primary care doctors—so they will have all the necessary tools to help prevent future illness and death because of heart disease after cancer treatment.