Early menarche and late menopause lead to an increased total lifetime number of menstrual cycles. If women who experience menopause between the ages of 45 and 55 are used as the reference group, then a 50% higher relative risk of subsequently developing breast cancer is present in women who experience menopause at 55 or older. A 30% lower relative risk of breast cancer is present in women who cease menstruating at age 45 or younger.

Common questions about your risk for breast cancer
Breast cancer is the second leading type of cancer in women, with roughly 175,000 new cases of invasive cancer diagnosed annually in the United States, and 44,000 women who die of the disease. Do not take to heart what you hear about an American woman’s “1 in 8” lifetime chance of developing breast cancer; it tells you little about your own personal risk. Whether you’re overestimating or underestimating your risk of developing breast cancer, keeping up important self-examinations and regularly scheduled screening mammographies remains the best advice for everybody.

Although most women greatly overestimate their risk of breast cancer and overlook their far greater likelihood of dying from heart disease, others do underestimate their personal, individual risk. How do you know where you stand? To give you - not a perfect - but a ballpark idea, the National Cancer Institute (NCI) is now offering its Breast Cancer Risk Assessment tool, an easy-to-use and free 3¹/₂-inch floppy “risk disk” to help you and your obstetrician-gynecologist try to sort out your risk (see “The risk disk: putting the numbers into perspective” for a sample calculation of how the program works). If your risk appears to be high, you may benefit from taking a drug that appears to prevent breast cancer.

Other risk factors for breast cancer (in descending order) include:

• Age older than 60 years

• Living in a developed country

• Previously having atypical breast hyperplasia

• Previously diagnosed lobular carcinoma in situ of the breast

• Having cancer in the contralateral breast

• Beginning menarche before age 11

• Having first child in early 40s

• Being exposed to abnormal levels of ionizing radiation as a young female after age 10

• First-degree relative whose breast cancer was diagnosed before age 40

• Using diethylstilbestrol during pregnancy

• Having postmenopausal body mass index greater than 35

• High intake of saturated fat

• Using HRT for 10 years or more

• Consuming too much alcohol

No Link Between Breast Cancer Risk, Abortion

Although women have a lifetime reduction in breast cancer risk if they have a full-term pregnancy before the age of 35, those who have a spontaneous or induced abortion are not at higher risk of developing the disease compared with the general female population, according to the results of a study published in the April 23 issue of the Archives of Internal Medicine.

Karin B. Michels, Ph.D., of Harvard Medical School and Brigham and Women’s Hospital in Boston, and colleagues conducted a study of 105,716 women aged 29 to 46 years old who were followed up from 1993 until 2003. During the follow-up period, there were 1,458 newly diagnosed cases of invasive breast cancer.

Among the study cohort, 16,118 women (15 percent) had a history of induced abortion, and 21,753 (21 percent) had a history of miscarriage. There was no association between single or multiple abortions and the likelihood of developing breast cancer.

“We observed associations in two subgroups, an association between induced abortion and progesterone receptor-negative breast cancer and an inverse association between spontaneous abortion before the age of 20 years and breast cancer incidence,” the authors write. They caution that “subgroup analyses have to be interpreted cautiously, especially if the strata are small. No obvious mechanisms can be provided for these subgroup findings; thus, chance has to be considered as a possible explanation.”

REFERENCES
_{1. Clemons M, Goss P. Estrogen and the risk of breast cancer. N Engl J Med. 2001;344:276-285.}

2. McPherson K, Steel CM, Dixon JM. ABC of breast diseases: breast cancer-epidemiology, risk factors, and genetics. BMJ. 2000;321:624-628.

Trudy Bush, Frederick Naftolin, Dahlia Sataloff. Breast cancer and the postmenopausal woman. Contemporary Ob/Gyn 2002;3:80-94.