Heart cancer: Insights on diagnosis, treatment and research
The heart pumps blood to send vital oxygen throughout the body. It’s a maze of four chambers: two on the left and two on the right. Blood enters the heart at the upper right chamber, which is called the right atrium. It’s pumped into the lower chamber, known as the right ventricle, which then sends blood into the lungs for oxygenation. The now oxygen-rich blood returns to the heart through the left atrium and moves to the left ventricle. From there, the blood is pumped across the entire body.
“The lion’s share of the pumping happens in the left ventricle, which is why the wall of the left ventricle is thicker than the other chambers,” says Vinod Ravi, M.D. He specializes in treating the rare tumors that grow in the heart.
Most cardiac tumors are benign, but some cancers can spread to the heart. And some tumors, called cardiac sarcomas, start in the heart.
Cardiac angiosarcoma is the most common primary cardiac sarcoma
Although sarcomas of the heart are rare, most cases are a subtype called cardiac angiosarcoma. They tend to develop from the cells that line the right atrium and rarely occur in the left chambers of the heart. Cardiac sarcomas that tend to occur on the left side of the heart include:
spindle cell sarcoma
undifferentiated pleomorphic sarcoma
Compared with left-sided cardiac sarcomas, cardiac angiosarcoma is typically more aggressive.
Although there are about 1.7 million new cancer cases yearly, only about 25 are cardiac angiosarcoma diagnoses. “It’s extraordinarily rare,” Ravi says. It’s also typically seen in adults younger than age 65.
Cardiac angiosarcoma symptoms mirror other heart or lung problems
Symptoms of cardiac angiosarcoma are typical of someone with a heart or lung problem. Most patients have some degree of chest pain and shortness of breath. “People note that they’re quick to get winded when doing routine activities,” Ravi says.
When experiencing these symptoms, patients often go to an emergency room and typically receive an electrocardiogram to check their hearts. However, an electrocardiogram can’t detect a mass, and because cardiac sarcomas are so rare, patients’ symptoms are often misdiagnosed. “A 30- or 40-year-old patient will have their symptoms written off as anxiety,” Ravi says. A mass in the heart can also be detected with an echocardiogram, but it requires a trained eye and further testing to differentiate it from more common things like a blood clot, Ravi says.
He advises patients to push their care providers to dig deeper to find explanations for the symptoms. “If you aren’t seeing anything with an echocardiogram, ask for a cardiac MRI. It can be very useful in diagnosing this condition,” Ravi says.
Vascular endothelial growth factor may fuel cardiac angiosarcoma growth
The blood that enters the right side of the heart is very different from the blood entering the left side. Since it hasn’t been oxygenated by the lungs yet, it has low oxygen levels.
It’s hypothesized that tumors on the right side of the heart may be fueled by vascular endothelial growth factor (VEGF), Ravi says. VEGF is a protein that helps grow blood vessels. The body typically produces it when there’s low oxygen to help increase blood flow and, therefore, oxygen supply.
“It’s very curious, but there hasn’t been a study to confirm the correlation,” Ravi says. “Unfortunately, because of the rarity of these tumors and the challenges with taking tumor tissue from the heart, there isn’t a lot of research explaining why these tumors grow more in the right atrium and what growth regulatory genes promote tumor growth. That’s the work in front of us,” he says.
Treatment takes on cardiac angiosarcoma
Because the heart is the source of our blood flow, cancer cells from cardiac tumors can move throughout the body. So, at the time of diagnosis, cancer has often already spread. Most commonly, cardiac angiosarcoma spreads to the lungs, bones, liver and brain.
“Unfortunately, one in four patients sees cancer spread to the brain, so that has to be addressed first,” Ravi says. He notes that sometimes brain metastasis doesn’t have symptoms, but still must be treated to avoid complications later such as seizures or bleeding in the brain. “If a brain lesion is identified, it has to be treated with stereotactic radiosurgery right away,” Ravi says.
If cancer hasn’t spread to the brain, treatment typically starts with a combination of the chemotherapy drugs doxorubicin and ifosfamide. Patients older than 65 may receive a less intensive combination of doxorubicin and dacarbazine. The goal is to have chemotherapy shrink the primary heart tumor as well as treat sites of metastasis throughout the body.
If the chemotherapy has reduced the primary tumor at the heart and there’s no evidence of disease elsewhere, Ravi says the patient’s body is allowed to rest. During that recovery period, the patient will ideally receive surgery to remove the primary tumor. “These tumors are notoriously hard to deal with surgically and require an expert team with experience operating on these tumors,” Ravi says.
After surgery, patients continue chemotherapy to help keep cancer from recurring.
Immunotherapy may extend survival
A team at MD Anderson is exploring immunotherapies to treat patients with angiosarcoma, including cardiac angiosarcoma. “We’re using immunotherapies to stimulate the immune system to help keep cancer from coming back,” Ravi says.
A recent study led by Ravi investigated the immune checkpoint inhibitor pembrolizumab in patients with cardiac angiosarcoma. “We saw that pembrolizumab pushes cancer to a more chronic disease state,” Ravi says. “Even without curative benefit, the drug appears to slow cancer’s progression substantially.”
Ravi says the key will be to monitor survival and see if immune checkpoint inhibitors extend patients’ lives. The next step in research will be to investigate immunotherapy combinations to make them more effective.
“These tumors are very challenging to treat, especially after they’ve spread, but we’re working to improve the survival numbers and bring the best results to patients,” Ravi says.