What can you do to protect yourself against breast cancer?
As we have seen, many of the risk factors involve things you cannot change: your age, your sex, your heredity. Others, like the age at which you marry and have children, depend on a number of psychological, social, and economic factors. Your best bet is to cut down on the risk factors you can control and to follow the recommended guidelines for early detection.
Can you reduce your risk of breast cancer by diet?
Having a diet high in fat may contribute to breast cancer. In fact, having a high-fat diet is not beneficial to your health in other ways. The standard dietary recommendation for general health is to eat five servings of fresh fruits and vegetables every day. The known vitamins in fruits and vegetables and the known fiber content are thought to protect against all kinds of cancer.
The type of fat you eat is at least as important as the total amount. Monounsaturated fats, including olive oil and canola oil, are linked to lower risk, while polyunsaturated fats, such as corn oil and tub margarine, and saturated fats, the kind found in meat, are associated with increased risk.
Although the data are controversial, some researchers believe a substance called lycopene in tomato sauce lowers breast cancer risk. Recently there has been scientific interest in flax seeds. Researchers have experimented with adding ground flax seeds to the diet, though the benefits have not been proven. Soy products seem to have a protective effect. Studies have shown that women from Asian cultures have a much lower incidence of breast cancer than women of Western cultures, but this advantage recedes when Asian women adopt a European or American diet.
Oily fish such as salmon and tuna that contain omega-3 fatty acids seem to be advantageous. Their use in preventing breast cancer cannot be proven, but they have other benefits and are worth emphasizing in your diet.
Does exercise have any influence on breast cancer risk?
This is a relatively new area of research and more work needs to be done. However, some research shows that women who exercise have less breast cancer than women who do not. This is true of both older postmenopausal women and women in the 15-44 age group. Some studies suggest that strenuous exercise in youth has a lifelong protective effect. Certainly obesity increases the risk of breast cancer, and exercise is one way to fight off extra weight.
What about the drug tamoxifen as a cancer preventive?
If you are at high risk for breast cancer, perhaps through your genetic background, talk to your doctor about taking tamoxifen as a cancer preventive. Tamoxifen is an antiestrogen drug used for many years to prevent the recurrence of breast cancer in women who had already had it. An American study completed in 1998 showed that women at high risk for breast cancer, whatever their age, substantially decreased their chances of getting the disease by taking tamoxifen. In fact, tamoxifen’s effectiveness in preventing breast cancer was so obvious that the study was stopped even before the allotted time had elapsed. Interestingly, the findings of European studies were more ambiguous.
The company that manufactures tamoxifen, AstraZeneca, has promoted a scale for calculating risks called the Gail Model Risk Assessment Test. It factors in a woman’s age, her age when she had her first menstrual period, her age when her first child was born, the number of first-degree relatives who have had breast cancer, the number of previous breast biopsies, and the presence (or absence) of atypia in these biopsies.
My own feeling is that every woman considering this preventive therapy should sit down with her physician and have a thorough discussion of all the pros and cons. It is fine to have a risk scale, but you cannot use it arbitrarily to decide who should use tamoxifen and who should not.
Does tamoxifen have side effects?
One side effect is that tamoxifen can put women who are close to menopause (peri-menopausal) into premature menopause. Tamoxifen blocks the action of estrogen, and estrogen is important at many sites in a premenopausal woman’s body.
A second side effect is it slightly increases the risk of uterine cancer. Women with a strong family history of uterine cancer or other risk factors for this disease must take these risks into consideration before starting tamoxifen. Every woman taking tamoxifen should have a gynecological exam at least every year and perhaps every six months.
Another risk is the development of deep-vein thrombophlebitis (inflammation of the veins and the formation of blood clots there). These clots can move through the circulatory system to the lungs, where they can be life threatening. So if a woman has a tendency to this condition or has had it previously, she should carefully consider whether tamoxifen is right for her.
How long can you take tamoxifen?
The standard recommendation for women who have had breast cancer is five years of therapy. Researchers are currently trying to develop a timetable for preventive tamoxifen therapy.
Does it matter when in your life you start tamoxifen?
This is a very important question, and the answer depends heavily on childbearing priorities. If a woman wants children, she should not use tamoxifen until she has finished her family.
Are there drugs other than tamoxifen that might help prevent breast cancer?
Current drug trials are comparing tamoxifen with a close relative, raloxifene, in terms of breast cancer prevention. Raloxifene was designed to prevent osteoporosis and has only been studied in postmenopausal women. The results of these trials are yet to come, so at present tamoxifen is the drug of choice.