Every week our journalist answers scientific questions from readers.
Published at 2:55 am. Updated at 7:00 a.m.
Why is there no heart cancer?
Claire Boissonneault
Heart cancer does occur, but it is very rare. This is because cells in the heart reproduce less than in other parts of the human body.
“Cancer arises in cells that can grow and divide regularly,” explains Nathaniel Bouganim, an oncologist at McGill University Health Center (MUHC). “The skin, mucous membranes, lungs, blood, for example. But once the heart is formed, there is almost no cell division. This reduces the likelihood of mutations and aberrations that occur during cell division. »
PHOTO PROVIDED BY THE AUTHOR
Nathaniel Bouganim
One of the most common tumors of the heart – although very rare – is rhabdomyosarcoma. “It is muscle cancer that can occur anywhere in the body, including the heart,” says Dr. Bouganim. It is often caused by radiation therapy near the heart. Or through a mutation present from birth that is activated over time. »
Another cancer, leiomyosarcoma, can affect the inner lining of the heart, but is even rarer. And it can happen that metastases from cancers from other organs contaminate the heart.
Difficult to treat
Heart cancer is very difficult to treat, says Dr. Bouganim.
These are primarily sarcomas, which are types of cancer for which there are only a few medications. Radiation therapy or surgery is required. Surgery on the heart is of course riskier.
Nathaniel Bouganim
Ramy Saleh, a colleague of Dr. Bouganim at MUHC, is one of two Quebec sarcoma specialists. “I see about one or two cases of cardiac sarcomas a year,” says Dr. Saleh.
He is working to build a referral network for sarcomas in Quebec to better treat them. This network currently includes 12 hospitals. “We can also carry out clinical studies more easily,” says Dr. Saleh. In the last two or three years we have seen clinical trials in the United States for five new sarcoma drugs. Unfortunately, it is not suitable for sarcomas of the heart, and medications for one sarcoma do not necessarily work for another sarcoma. »
Sarcomas – there are around a hundred – are, in a sense, the oncological equivalent of “orphan diseases”, and are very rare, says Dr. Saleh.
How are sarcomas defined? “What they all have in common is that they are resistant to chemotherapy because they affect tissues in which there are not many blood vessels that can transport the chemotherapy drugs there,” explains Dr. Saleh. Sarcomas also have fewer mutations, reducing the number of targets for chemotherapy. They are also very aggressive. » A 40-year study found that the proportion of patients who are still alive five years after being diagnosed with cardiac sarcoma is 11%. According to the Canadian Cancer Society, this five-year survival rate is 89% for breast cancer and 22% for lung cancer.
Aren’t there many blood vessels in the heart? “Yes, but heart surgery is very delicate,” says Dr. Saleh. And there are not many molecules available for chemotherapy. »