BREAST CANCER: ASSESSING ROLE OF HORMONES
By JANE E. BRODY
Published: June 23, 1986
Breast cancer, a disease that will strike one in 11 American women, has in the last few years forced researchers back to square one in their efforts to understand its causes and develop methods of prevention.
Based on early findings from new studies, some experts now predict that manipulation of a woman's hormones through diet and exercise or perhaps simple drug therapy may help to keep the disease at bay.
The suggested changes involve following a low-fat or low-calorie diet throughout life and pursuing vigorous physical activity, especially during the teens and early adult years.
Although a decade or more of research needs to be completed before the effectiveness of such measures is fully known, the investigators point out that good diet and exercise habits can only help, not hurt.
At the least, they would reduce the risk of developing heart disease and obesity and its attendant health problems.
''We have tended to think of cancer as something that comes from the outside, perhaps from a virus or chemical exposure,'' said Dr. Brian Henderson, a cancer epidemiologist at the University of Southern California in Los Angeles.
''Breast cancer comes from within. It is not caused by smoking, alcohol or exposure to chemicals. It is caused by the amount of hormones a woman produces, and the solution to this problem will depend on what women can do to influence these hormones.''
The new studies are an outgrowth of frustration with the inconsistency of early leads and the failure of those leads to result in reasonable preventives. As Dr. Steven D. Stellman, an epidemiologist with the American Cancer Society, put it, ''It's really very depressing that after all this work we don't know much more about the causes of breast cancer than we did 20 years ago.''Dr. Robert Hoover, chief of environmental epidemiology at the National Cancer Institute, said: ''The ideas of the last 10 or 15 years were too simplistic. Now we have to look at much more complex interactions before we can say who is most likely to get this disease and maybe find some way to stop it.''
For example, a recent study by the American Cancer Society of nearly 366,000 middle-aged and elderly women revealed that the long-established ''risk factors'' for breast cancer, including the fact that a mother or sister had the disease, could account for only about 25 percent of cases. In three-fourths of the women who developed breast cancer during the six years of annual checkups, there was no particular circumstance to suggest they might get it.
In addition to family history, the researchers, Herbert Seidman, Margaret H. Mushinski and Dr. Stellman looked at such widely accepted risk factors as previous surgery for be-nign breast disease, having never married or had children, giving birth for the first time after age 30, starting to menstruate before 12 and undergoing menopause after 50. They concluded that at this stage of research, doctors must consider every American woman at high risk of developing breast cancer, and they recommended periodic examinations of all women in an effort to detect the disease early enough to cure it.
Researchers are particularly eager to sort out the relevant factors in breast cancer risks now that so many millions of women take hormones daily, either to prevent pregnancy or to alleviate the symptoms and aftereffects of menopause. Thus far, several studies have shown no effect of birth control pills on a woman's chances of developing breast cancer. And although postmenopausal estrogens taken for 10 years or longer do double the risk, they lower a woman's overall risk of death because they help to prevent the far more common problem of coronary heart disease and also protect against osteoporosis, a weakening of the bones. Pregnancy After Age 30
Another growing concern researchers are eager to address is whether the large numbers of women who today are having their first child after age 30 are, in the process, significantly increasing their breast cancer risk. In the past, Dr. Stellman pointed out, most such women had late first pregnancies not by choice but because of infertility problems. He said: ''It may have been the hormone imbalance causing their infertility, not the late first pregnancy itself, that increased their breast cancer risk. If that's true, women who deliberately delay childbirth may have nothing to worry about.''
Not everyone is so sanguine about late childbearing. ''The risk of breast cancer increases rapidly for every month that passes before a woman's first full-term pregnancy,'' Dr. Henderson of U.C.L.A. said. Explaining his theory about why this may occur, he said analyses conducted by his group at the university indicate that the protection afforded by an early first pregnancy may result from a temporary turnoff of breast-stimulating estrogen hormones at a time when breast tissue is aging most rapidly.
''If a woman waits until she is 35 or older to have her first child, there's not enough time to get the full benefit of the estrogen turnoff during the second two-thirds of pregnancy,'' Dr. Henderson said. In fact, he said, ''There's a net overall negative effect of having a first child late in life, perhaps because the surge of estrogen during early pregnancy stimulates the growth of precancerous breast tumors, which are more likely to be present in older women.''