Breast Cancer : The Estrogen Connection, Anatomy of a Disease

by Food and Drug Administration (FDA)

(Page 2 of 3)

Of increasing interest is the possible relation of a high-fat diet to breast cancer. The death rate from breast cancer is highest in countries, including the United States, in which the intake of fat and animal protein is high. For instance, Japanese women historically have a low risk for breast cancer, but that risk has been rising dramatically, concurrent with a "Westernization" of eating habits; that is, from a low-fat to high-fat diet. Within Japan, the risk is 8.5 times higher for wealthier women, who eat meat daily, than among poorer women.

When large populations move from a low-incidence area to a high-incidence area and adopt the local lifestyle, they tend to take on the cancer risk patterns of their new homeland. Among immigrants from Asia to the United States, the incidence of breast cancer typically rises somewhat in the first generation, then continues to rise in subsequent generations until it approaches that of the United States.

A study involving nearly 57,000 women, published in the March 6, 1991, Journal of the National Cancer Institute, found an association between breast cancer and fat intake that, the authors say, "appears unlikely to have arisen by chance," even though the link is not strong and two previous studies contradict their results. It could be that the issue is muddled because the difference in fat content between the lower fat and higher fat diets of the women studied may not be great enough to influence breast cancer development. Americans typically consume 40 percent of their calories in fat. A reduction to 30 percent may not be significant in reducing breast cancer risk.

To examine the question further, NCI has approved funding for a 15-year trial that includes 24,000 women aged 50 to 69 who typically eat 38 percent of their calories from fat. Forty percent of the women will be taught how to follow a diet with only 20 percent of calories from fat, and the rest will follow their usual diet. The study will compare the incidence of breast cancer, colorectal cancer, heart disease, and overall mortality between the two groups.

Meanwhile, Bates advises that, "although there is not a definitive answer to the dietary fat hypothesis, the link seems to be plausible, and efforts to alter our diet would appear prudent."

The Estrogen Connection

These risk factors may appear unrelated, but a possible common thread may be estrogen. Estrogen causes breast cells to grow, and there may be times in a woman's life when the breast is more susceptible to cancer-causing substances in the environment.

"Most of the risk factors listed can in some way increase the exposure to estrogen," says Bates. "A longer menstrual history, the additional estrogens from birth control pills or from estrogen replacement at menopause, even a high-fat diet, alcohol, or just being overweight may increase the amount of estrogen in the bloodstream, or may increase the amount available to the woman's breast tissue."

An American Cancer Society study published in 1982 analyzed the contribution of 10 common risk factors by following more than 365,000 white women 30 to 84 years old for six years. One telling conclusion was that three-quarters of all breast cancer cannot yet be attributed to any known specific cause. "From the point of view of the clinician," the authors state, "all women should be treated as being at appreciable risk for breast cancer."

Nevertheless, it is important to remember that having one or more risk factors does not mean that a woman is certain, or even likely, to develop breast cancer. It means only that she may be at statistically greater risk than another woman.

Despite the continuing rise in the incidence of breast cancer, the death rate has remained fairly stable over the past 50 years. This can be attributed largely to earlier detection.

Anatomy of a Disease

The breast is a gland designed to produce milk. Milk ducts leading to the nipple originate from lobules inside 15 or 20 lobes arranged like spokes around a wheel. The spaces around and between the milk-producing lobes are filled with fat. Ninety percent of breast cancers arise from the milk ducts. When ductal carcinoma, as it is called, remains confined to the duct, it is called in situ, or intraductal, cancer. When the cells penetrate the walls of the duct and invade surrounding tissue, it is called invasive ductal cancer. About 5 percent of breast cancers are lobular carcinomas, which originate in the lobules.

Two atypical kinds of breast cancers are inflammatory breast carcinoma and Paget's disease. Whereas most breast cancers are slow growing and painless, inflammatory breast carcinoma progresses very rapidly and is painful, with symptoms resembling an infection. The breast is warm and reddened, and the skin may appear pitted like an orange peel. In Paget's disease the nipple becomes crusted; cancer cells grow upward along the ducts from a malignancy deeper in the breast.

When an abnormality is detected in the breast by mammography, the doctor may recommend a biopsy. If a lump is found by palpation (feeling the mass), a biopsy is almost always necessary, regardless of the results of mammography. Exceptions may be certain lumps found in women who have histories of lumpy or cystic breasts.

The biopsy — surgical removal of all or part of the lump or suspicious area — allows a pathologist to examine the tissue and determine with certainty whether or not the lesion is cancerous. Eighty percent of palpable lumps are benign (not cancerous).

Biopsy does not always require hospitalization. It can be done as an outpatient procedure. Also, some biopsies are done by fine needle aspiration, using a local anesthetic. The doctor inserts a needle into the lump and tries to withdraw fluid. If it is a cyst, it will collapse when the fluid is removed. If it is solid, the doctor may remove some cells with the needle to send to the laboratory for analysis.

The common practice nowadays is to do a biopsy first and then schedule surgery, if necessary, within the next few weeks. Some women may still opt for the one-step procedure that was routine when Joyce Fine had her mastectomy. (Until the late 1970s, it was standard procedure for the patient having a biopsy to sign a consent form permitting the surgeon to remove the breast at the same time if the tumor was found to be cancerous.)

The interval with the two-step procedure, however, allows the woman time to find out about and choose among her treatment options, get a second opinion, and prepare for her hospital stay. The brief delay in treatment does not reduce the chances for a successful outcome. Some states have passed laws requiring that women be told a two-step procedure is their legal right and, in some cases, that they be given specific information about their options.

About the Author

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