Researchers have known for years that people who are active and maintain a healthy weight are
less likely to develop cancer, and cancer survivors who exercise and keep a healthy weight are less likely to relapse. Only recently, however, have scientists begun to understand how staying active helps prevent cancer from developing or relapsing. Could this be the key to healthy aging?
According to Patricia Ganz, a breast cancer specialist at UCLA’s Jonsson Comprehensive Cancer Center, while exercise may not change the inner workings of a tumor cell, physical activity may change the cell's “neighborhood”—the surrounding tissue, blood vessels and immune cells —known as the "microenvironment.”
“Healthy neighborhoods are as important to cells as they are to children”, says William Li, president of the Boston-based Angiogenesis Foundation, which funds research in cancer and other diseases.
He compares a lone tumor cell to a "bad kid" living in a good neighborhood. Even an aspiring juvenile delinquent won't be able to cause much trouble if he's surrounded by watchful parents, neighbors and local police. Exercise helps improve the neighborhood, keeping cancers in check, Li says. Failing to exercise—and putting on a lot of weight—damages the neighborhood, making it easier for cancers to grow out of control.
In particular, exercise helps to prevent chronic inflammation, a process that can fuel cancers by changing the neighborhood around a tumor cell. Exercise helps lower levels of both insulin and sex hormones, such as estrogen, which release growth factors that let tumor cells survive and spread, Li says. And, as Dr. Ganz points out, exercise also helps relieve psychological stress, which may further reduce inflammation.
While these discoveries are exciting, there are still many unknown causes of cancer. “We don't want women with breast cancer to feel like they caused their breast cancer or that they caused it to come back”, says Pamela Goodwin, professor of medicine at Mount Sinai Hospital, University of Toronto.
Still, doctors are discovering more and more ways that a tumor’s environment can stop cancers before they start or spread. Doctors already target the tumor neighborhood with drugs such as Avastin, which cut off a cancer's blood supply.
“Learning more about the microenvironment may provide new tools, such as drugs that curb inflammation to prevent cancer or treat it more effectively”, Ganz says.