The endometrium is the inner layer of tissue lining the uterus. In a healthy, pre-menopausal woman, the endometrium thickens in the weeks leading up to ovulation. If a pregnancy occurs, the fertilized egg uses the nutrients in the lining to grow and develop until the umbilical cord is established. If the egg is not fertilized (no pregnancy), the lining is shed (menstruation).
Endometrial cancer is a type of cancer that develops in abnormal cells of the endometrium. According to the American Cancer Society, about 43,470 cases will be diagnosed in the U.S. this year. Roughly 7,950 women will die from it. The cancer is most common in women 50 and older.
Estrogen exposure may play a role in development of endometrial cancer. Rates are higher in women who take estrogen therapy or tamoxifen for breast cancer (the drug acts like estrogen on the uterus), those who start menstruation at a young age and/or undergo menopause at a later age, women with a certain type of ovarian tumor (granulose-theca, which can make estrogen), and those with polycystic ovarian syndrome.
Health experts sometimes divide endometrial cancer into two types. Type 1 cancers are typically slow to grow and spread. They are usually caused by exposure to excessive levels of estrogen. Type 2 endometrial cancers are much more aggressive and likely to spread. The cancer cells look very different from normal endometrial cells. It is much less common than type 1.
The Breast Cancer/Endometrial Cancer Link
Researchers have known that women with breast cancer have a higher risk of developing endometrial cancer. This is particularly true for patients who have taken the medication, tamoxifen. In the breast, tamoxifen acts as an anti-estrogen agent, thus helping to prevent and treat breast cancer. But in the uterus, it acts like estrogen, thus exposing the endometrium to more estrogen. However, according to the American Cancer Society, the risk for endometrial cancer in women taking tamoxifen is small, about one in 500.
There are usually few warning signs for endometrial cancer. In spite of this, health experts currently do not recommend routine endometrial biopsies or transvaginal ultrasound for women who have taken tamoxifen. However, those who develop unusual symptoms (like abnormal vaginal bleeding, pelvic pain or unexplained weight loss), should see a physician for a further diagnostic workup.
A New Concern
Researchers at Arizona Cancer Center and the University of Arizona in Tucson, AZ, say there’s another concern for women with breast cancer- some of these patients may develop a highly aggressive form of endometrial cancer. The investigators looked at medical records of breast cancer patients over approximately a ten-year span. Researcher Wenxin Zheng, M.D., says about 20 percent of the women were eventually diagnosed with type 2 endometrial cancer, the type that is more likely to spread. Normally, only three percent of women develop type 2 endometrial cancer. Since there are rarely symptoms associated with the cancer, the disease has often already spread by the time it is diagnosed. Thus, the women need much more aggressive therapy. Five-year survival rate for those with advanced cancer is only about 40 percent.
Gynecologist Setsuko Chambers, M.D., says the link was especially strong in women who were diagnosed with breast cancer before 55. However, further studies need to be done to validate the findings. At this point, routine screening for asymptomatic patients is not recommended. However, breast cancer patients who have taken tamoxifen and have other risk factors for endometrial cancer should be aware of their risk for type 2 endometrial cancer.
AUDIENCE INQUIRYFor general information on endometrial or breast cancer:
American Cancer Society, http://www.cancer.org
National Cancer Institute, http://www.cancer.gov
BIBLIOGRAPHYBulun, Serdar, et al., “Aromatase Excess in Cancers of Breast, Endometrium and Ovary,” The Journal of Steroid Biochemistry and Molecular Biology, 2007, Vol. 106, No. 1-5, pp. 81-96.
Kim, Ho Sung, et al., “The Effect of Adjuvant Hormonal Therapy on the Endometrium and Ovary of Breast Cancer Patients,” Journal of Gynecologic Oncology, December 2008, Vol. 19, No. 4, pp. 256-260.
Noh, Soo-Kyung, et al., “A Case of Report of Quadruple Cancer in a Single Patient Including the Breast, Rectum, Ovary, and Endometrium,” Journal of Gynecologic Oncology, December 2008, Vol. 19, No. 4, pp. 265-269.
Polin, Sandra, and Susan Ascher, “The Effect of Tamoxifen on the Genital Tract,” Cancer Imaging, June 30, 2008, Vol. 8, pp. 135-145.