Larry Norton, MD, is attending physician and member, Memorial Hospital, and head of the solid tumor division, Memorial Sloan-Kettering Cancer Center, and president of the American Society of Clinical Oncology.
On a cellular level, what is cancer?
All the tissues in the body know to grow to a certain size and to perform certain functions. When something goes wrong with the instructions in certain cells, they do several things that are abnormal, and these are things that we call cancer. Too many cell divisions occur so you get a lump, a mass. These cells spread into surrounding tissue and develop the capacity—and this is the serious part—to grow in other parts of the body.
So a breast cell, for example, should normally remain a small collection of cells in the breast. If it grows too large you get a lump; if it invades into the surrounding breast tissue you call that invasive breast cancer; and if it spreads to other parts of the body such as the lymph nodes under the arm or to the lung or liver or bone we call that metastasis. Those three things: forming a lump, spreading into surrounding tissue, and spreading to other parts of the body are the behaviors that we associate with cancer.
How does that kill you?
Well, the big problem is that if the cancer cells can spread to another part of the body and can grow to a large size and invade into, surrounding tissues they can destroy the function of those organs. For example, if a breast cell becomes cancerous and spreads to the lung, it can grow its masses in the lung, spread throughout the lung and disturb the function of the lung so the lung can't exchange oxygen with the air anymore, depriving the person of oxygen. . . . That's the real problem with cancer: it's not the local disease, the mass of growth in the local area. For the most part it's the ability of cancer cells to spread to other parts of the body.
Can you summarize the risk factors?
The biggest risk factor for developing breast cancer is being a woman. Women have about a hundred times greater chance of developing breast cancer than a man. We think this is because estrogen promotes the growth of breast cells and can lead to the growth of cancer cells by a variety of mechanisms that we're now just beginning to understand. Certain things increase the risk, however.
