Understanding how family ties relate to breast cancer


March 22, 1994|By Dr. Genevieve Matanoski | Dr. Genevieve Matanoski,Medical Tribune News Service

For women who have watched their female relatives die at young ages from breast cancer, the fear of this disease is almost incapacitating -- it can dominate their lives.

Consider the case of one 30-year-old woman whose mother died at age 42 from breast cancer and who has just learned that her 34-year-old sister has the same disease. What can we tell her when she asks: "Am I going to get breast cancer?"

There is no simple answer to her question -- and her anguish is understandable.

Q: What is the relationship between the risk of developing breast cancer when we have a family member with the disease?

A: I always caution women to avoid the confusion among the terms genetic, familial and heredity. Cancer is the result of genetic changes in cells. We say that because cancer is caused by alterations in the DNA, the material which contains genes and which is the center of cellular information, that does not necessarily mean that a woman inherited those changes in DNA from her parents.

In fact, most changes in DNA occur because of changes in our body, exposure to our environment and our lifestyle. So even though there may be a familial history of cancer, you may not have inherited a susceptibility to the disease. There are common exposures and lifestyle characteristics that occur in families. These, too, may lead to cancer.

Women, especially those who have watched others in their family battle breast cancer, need to remember that they may just be seeing the results of the law of averages. Breast cancer is common in women. Over your whole lifetime, the risk of developing breast cancer is about one in 10. So we need to remember that with women living longer, it is likely that many women will know someone in their family who has had breast cancer.

Q: How can I tell if I have an inherited susceptibility?

A: Right now the only way is to examine your family history. But remember that even though a woman can inherit the gene from either the father or the mother, the chances of her getting it are still only 50 percent.

In looking at susceptibility, we look first at the number of first-degree relatives with either breast or ovarian cancer. Women with mothers and/or sisters with breast cancer are reported to have a 1.6 times to 3 times greater risk of breast cancer. If you have only a second-degree relative with breast cancer, the risk is lower.

If we look at the age of the onset of the disease in family members, we see that the risk is increased four to six times if the relative developed cancer before the age of 50. Breast cancers in close relatives and more than one relative, as well as onset of the disease before the age of 50 in these women, suggest there is a tendency in the family toward an inherited risk of the disease.

Clearly, this combination of circumstances is not common. Remember, too, that most women with family histories have only a slightly elevated risk.

Dr. Genevieve Matanoski is a physician and epidemiologist at the Johns Hopkins School of Hygiene and Public Health. She is a founding director of the school's Institute for Women's Health Research and Policy.

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