While a personal history of endometrial cancer—cancer of the uterine lining—has been linked to a higher risk of breast cancer, a new study finds that a family history of breast cancer does not increase the chances that women will develop endometrial cancer. The study, which followed nearly 38,000 women over a 14-year period, should help ease concerns about endometrial cancer among women whose families have been affected by breast cancer.

Endometrial cancer is a disease affecting the lining of the uterus. The American Cancer Society estimates that approximately 39,300 women will be diagnosed with uterine cancer in 2002, and 95% of these diagnoses will be endometrial cancer. Approximately 6, 600 Americans will die from uterine cancer this year. Eighty-four percent of women diagnosed with endometrial cancer live five or more years after their diagnosis.

To examine the relationship between endometrial cancer and a family history of breast cancer, Neely Kazerouni of the National Cancer Institute and colleagues followed 37,583 women from 1979 to 1998. The researchers collected information on the breast cancer history of the women’s mothers, sisters, daughters, aunts, and grandmothers. A total of 648 women were diagnosed with endometrial cancer during the follow-up.

After taking into consideration established risk factors for endometrial cancer (see bulleted list below), the researchers determined that a family history of breast cancer did not increase the risk of endometrial cancer in the study. However, they did find a personal history of breast cancer increased endometrial risk by 30%.

The results confirm two previous studies which also failed to find an association between endometrial cancer and a family history of breast cancer. A study published in 1972 did find a link between endometrial cancer risk and a family history of breast cancer, but Kazerouni’s team commented that the study included women with two or more relatives with breast cancer; thus, the families may have had a higher than average predisposition to cancer.

The current study did find a non-significant increased risk of endometrial cancer among women with a first-degree family member (mother and/or sisters) with bilateral breast cancer (cancer in both breasts). However, because other factors typically associated with inherited cancer (such as an early age at diagnosis) were not seen in these cases, the researchers are not inclined to believe that genetics played a key role in these cases.

Thus, a family history of breast cancer does not seem to be an important endometrial cancer risk factor; although a personal history of breast cancer does increase the risk of developing endometrial cancer. The researchers suggest that environmental, hormonal and/or genetic risk factors may be responsible for this link.

Risk factors for endometrial cancer include:

• Advancing age
• Family history
• Early onset of menstruation (before age 12) or late menopause (after age 50)
• Never having children
• Use of the breast cancer drug tamoxifen
• Estrogen therapy among women with intact uteruses (progesterone counteracts risk)

Risk factors for breast cancer include:

• Advancing age
• Family history
• Genetic predisposition (such as mutations of BRCA1 or BRCA2 gene)
• Early onset of menstruation (before age 12) or late menopause (after age 50)
• Never having children or having a first child after age 30
• Long term hormone replacement therapy (more than five years)

• The report, "Family history of breast cancer as a determinant of the risk of developing endometrial cancer: a nationwide cohort study," is published in the November 2002 issue of the Journal of Medical Genetics, http://jmg.bmjjournals.com/
• To learn more about endometrial cancer, please visit the American Cancer Society website at http://www.cancer.org/