An exceptionally well-done study on mice shows how exercise can be an important part of the treatment for cancer. Mice implanted with breast cancer cells who were given chemotherapy and exercise had much smaller and fewer tumors than those given the same chemotherapy but no exercise. Mice who ran but did not receive chemotherapy also had smaller tumors and signs of increased cancer cell death.
Cancers Grow Without Oxygen
Solid cancerous tumors produce a large number of new blood vessels around themselves, much more than normal tissues do. These new blood vessels become so numerous that they crowd each other and curl around and pinch the blood vessels to actually block the oxygen-rich flow of blood to the tumors. Tumors grow faster without oxygen, so the extra blood vessels produced by cancerous tumors actually deprive the cancers of oxygen to make them grow faster. Since lack of oxygen harms normal cells and helps cancerous cell to grow, lack of oxygen helps cancers grow faster so they may invade and destroy normal cells.
Why Cancers Can Grow Without Oxygen and Normal Tissue Cannot
Inside of every normal cell (except mature red blood cells) are tiny areas called mitochondria. All normal cells get their energy from two chemical pathways:
• the Krebs Cycle (inside mitochondria – uses oxygen), and
• glycolysis (outside the mitochondria but inside the cell – does not need oxygen).
The main source of energy for normal cells is the Krebs cycle, inside the mitochondria. Cancer cells have defective mitochondria, so their main source of energy is glycolysis, the turning of sugar into energy without needing oxygen. The extra blood vessels that overcrowd each other to block the flow of oxygen around a tumor actually cause the cancer to grow and the normal cells to die. This can spread the cancer.
Chemotherapy drugs are all poisons that kill normal cells as well as cancerous ones. Doctors using chemotherapy hope that most of the chemotherapy poisons will go to the cancers without killing the patient.
How Exercise Can Help Cancer Treatment
Exercise increases the flow of blood to all areas of the body, so if a patient exercises while being given chemotherapy, more blood will flow to and around the cancer. This increases the amount of oxygen and chemotherapy drugs brought to the cancer cells. The extra oxygen nourishes normal tissue and helps it to grow, while interfering with the cancerous tissue. Furthermore, the extra oxygen can help to revive the damaged mitochondria in the cancerous cells, which could turn the cancerous cells back into normal cells.
Caution: The American Cancer Society recommends exercise for all cancer patients who can tolerate it. However, they should check with their doctor before starting a new exercise program or continuing an existing program.