Every week, our journalist answers scientific questions from readers.
Why doesn’t heart cancer exist?
Claire Boissonneault
Heart cancers exist, but are very rare. This is because cells in the heart reproduce less than those in other parts of the human body.
“Cancers occur in cells capable of growing and dividing regularly,” explains Nathaniel Bouganim, oncologist at the McGill University Health Center (MUHC). “The skin, mucous membranes, lungs, blood, for example. But the heart, once formed, has almost no cell division. This gives less chance of mutations and aberrations, which occur during cell divisions. »
PHOTO PROVIDED BY THE AUTHOR
Nathaniel Bouganim
One of the most common tumors of the heart – although very rare – is rhabdomyosarcoma. “It’s a muscle cancer that can occur anywhere in the body, including the heart,” says Dr.r Bouganim. It is often caused by radiation therapy near the heart. Or by a mutation present from birth, which is activated over time. »
Another cancer, leiomyosarcoma, can strike the lining of the heart, but is even rarer. And it can happen that metastases of cancers from other organs contaminate the heart.
Difficult to treat
Heart cancers are very difficult to treat, says Dr.r Bouganim.
These are mainly sarcomas, which are types of cancer for which there are few medications. Radiotherapy or surgery is required. In the heart, obviously, surgery is riskier.
Nathaniel Bouganim
A colleague of the Dr Bouganim at the MUHC, Ramy Saleh, is one of two Quebec sarcoma specialists. “I see about one or two cases of heart sarcoma per year,” says Dr.r Saleh.
He is working to set up a Quebec reference network for sarcomas, in order to better treat them. This network currently includes 12 hospitals. “We will also be able to more easily carry out clinical studies,” says Dr.r Saleh. Over the past two or three years, we have seen clinical studies in the United States for five new drugs for sarcomas. Unfortunately, it is not for sarcoma of the heart, and medications for one sarcoma do not necessarily work for another sarcoma. »
Sarcomas – there are around a hundred – are in a way the oncological equivalent of “orphan diseases”, very rare, according to Dr.r Saleh.
How are sarcomas defined? “What they have in common is that they are resistant to chemotherapy, because they strike tissues where there are not many blood vessels that can carry chemotherapy drugs there,” explains D.r Saleh. Sarcomas also have fewer mutations, which reduces the number of targets for chemotherapy. They are also very aggressive. » A 40-year study showed that the proportion of patients still alive five years after the diagnosis of cardiac sarcoma is 11%. This five-year survival rate is 89% for breast cancer and 22% for lung cancer, according to the Canadian Cancer Society.
Aren’t there many blood vessels in the heart? “Yes, but it is very delicate to operate in the heart,” said Dr.r Saleh. And there are not many molecules available for chemotherapy. »