Ovarian and Uterine Clinical Resource Area - Disease Overview

Uterine Cancer

Normal Anatomy and Physiology

• Body of Uterus - The uterus, or womb, is the main female internal reproductive organ. The fertilized egg, or zygote, implants in the uterus and thus becomes an embryo. This is where the embryo develops into a fetus and finally into a baby. The uterus is lined with powerful muscles to push the child out during labor.
• Perimetrium - The outer layer of the uterus is called the epimetrium or perimetrium.
• Myometrium - This is the middle layer of the uterus which is composed of smooth muscle.
• Endometrium - This is the inner most layer of the uterus that is very thin and vascular. This layer is shed during menstruation. There is a collection of blood in the endometrium due to hormones in the body prior to menstruation. When the egg does not get fertilized, the body sheds the layer of blood that is vital for the fertilized egg to implant and grow.

Epidemiology
Endometrial cancer is both the most common type of uterine cancer and the most common cancer of the female reproductive system, accounting for approximately 6 percent fo all cancers in women. It is estimated that approximately 39, 080 women will be diagnosed in 2007 with uterine cancer accounting for 6% of all new cancers in women.

While the mortality rate has declined slightly over the past 20 years among white women, it has remained stable among other racial and ethnic groups. Although the incidence rate of endometrial cancer is lower for African American women than whites, the mortality rate is nearly twice as high. An estimated 7,400 women will die in 2007 from uterine cancer accounting for 3% of all cancer deaths in women.

Endometrial cancer occurs in both premenopausal (25%) and postmenopausal women (75%). The most commonly affected age group is between 50 and 59 years of age. Most endometrial cancer is diagnosed at an early stage because of postmenopausal bleeding. The five year survival rate is 96% if diagnosed at an early stage.

Risk Factors

• Age - Cancer of the uterus occurs mostly in women over age 50.
• Endometrial hyperplasia - The risk of uterine cancer is higher if a woman has endometrial hyperplasia.
• Hormone replacement therapy (HRT) - HRT is sometimes used to control the symptoms of menopause, to prevent osteoporosis (thinning of the bones), and to reduce the risk of heart disease or stroke.

Women who use estrogen without progesterone have an increased risk of uterine cancer. Long-term use and large doses of estrogen seem to increase this risk. Women who use a combination of estrogen and progesterone have a lower risk of uterine cancer than women who use estrogen alone. The progesterone protects the uterus.

• Obesity and related conditions. The body makes some of its estrogen in fatty tissue. Therefore, high levels of estrogen may be the reason that obese women have an increased risk of developing uterine cancer. The risk of this disease is also higher in women with diabetes or high blood pressure (conditions that occur in many obese women).
• Tamoxifen. Women taking the drug tamoxifen to prevent or treat breast cancer have an increased risk of uterine cancer. This risk appears to be related to the estrogen-like effect of this drug on the uterus.

The benefits of tamoxifen to treat breast cancer outweigh the risk of developing other cancers. Therefore, it is important to monitor women taking tamoxifen for possible signs or symptoms of uterine cancer.

• Race - White women are more likely than African-American women to get uterine cancer.
• Colorectal cancer - Women who have had an inherited form of colorectal cancer have a higher risk of developing uterine cancer than other women.

Other risk factors are related to how long a woman's body is exposed to estrogen. Women who have no children, begin menstruation at a very young age, or enter menopause late in life are exposed to estrogen longer and have a higher risk.

Most women with endometrial cancer have a history of unopposed and increased levels of estrogen. One of estrogen's normal functions is to stimulate the buildup of the endometrial lining of the uterus. Excess estrogen administered to laboratory animals can produce endometrial hyerplasia, which is a precursor for cancer.

Prevention and Screening
The addition of progestin to estrogen therapy used as hormone replacement therapy will decrease the risk of developing endometrial cancer or precancerious lesions such as atypical hyperplasia.

The use of oral contraceptives by premenopausal women is associated with a decreased risk of developing endometrial cancer ranging from a 50% decrease after 4 years of use, to a 72 % decrease after 12 or more years of use.

A the risk of developing endometrial cancer is increase in women who are obese, eating a diet low in saturated fats, high in fruits and vegetables, and rich in soy products may have a reduced risk of endometrial cancer. Also, women who exercise regularly tend to have a reduced risk of endometrial cancer.

Having children and breastfeeding children may be associated with a reduced risk of developing endometrial cancer.