Cancer Basics: An Interview with Larry Norton, M.D.

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.

Breast cancer's more common as a woman gets older. Taking extra estrogen, either in the form of birth control pills or hormones after menopause, definitely increases the risk of breast cancer to a small degree but to a significant degree in some individuals.

We've recently learned something very important: that some women are pre-disposed to getting breast cancer at a very high rate because of abnormalities in the genes that they inherit from their mother or their father. Two genes in particular —one called BRCA1 and the other called BRCA2—are definitely implicated in a high risk of developing breast cancer and ovarian cancer sometime in the woman's life.

Women who have menopause very late or start to have their periods very early seem to have a higher risk.

Not bearing a child until you're older—in your thirties—seems to increase your risk to some extent.

Radiation exposure for the few individuals who've had that unfortunate experience increases your risk.

And we're beginning to understand all these things on the basis of the changes in the DNA that lead to the formation of the cancer.

Why is breast cancer an epidemic in the West?

Well, epidemic or endemic, one could argue about the definition, but it's a very common disease, and that is something that we are concerned about and are studying very carefully. Nobody's really sure why this is the case, whether it's something that is related to the diet . . . various other lifestyle factors—not having many children and having your first child later—it's also possible that there are certain environmental chemical that we're exposed to or other environmental factors we're exposed to. All these things are under very careful study right now.

Are girls born today going to be as worried when they grow up as their mothers are today about this killer disease?

Well I find it hard to believe, frankly, that a little girl born today is ever going to have to worry about breast cancer. I mean we're talking about somebody who is going to see a world 35, 40, 45, 50 years from now. It's not going to look anything like this world in terms of medical therapy ...

I mean when I consider what's happened over the last decade, the advances have been so remarkable and the pace of knowledge expansion has been so extraordinary that I think even 10 years from now it's going to be an entirely different world in terms of cancer prevention, cancer diagnosis, and cancer therapy ... I would feel very safe if I were being born today in terms of having to deal with cancer in the future.