Understanding endometrial cancer - the basics

What is endometrial cancer?

Various conditions, both benign and cancerous (malignant), can affect the uterus, the hollow, pear-shaped organ in which a baby grows. Fibroid tumours on the uterine wall are benign (non- cancerous), and women who have them are not at increased risk of uterine cancer. Abnormal growth of cells in the lining of the uterus - called the endometrium - is known as endometrial hyperplasia. It is the most serious benign uterine condition and in some women it evolves into endometrial cancer.

Most uterine cancers arise in the endometrium and are called endometrial cancer or endometrial carcinoma. A more aggressive form, uterine sarcoma, develops in the wall of the uterus and accounts for fewer than 5% of all cases.

If left untreated, endometrial cancer can penetrate the wall of the uterus and invade the bladder or rectum, or it can spread to the vagina, fallopian tubes, ovaries and more distant organs. Fortunately, endometrial cancer grows slowly and is usually detected before spreading very far.

What causes it?

Endometrial cancer is a disease of older (usually post-menopausal) women. More than 95% of these cancers occur in women over the age of 40, with an average age of 63 years at the time of diagnosis. Post-menopausal women are at high risk of endometrial cancer if they:

• Began menstruating early
• Went through the menopause late
• Are overweight/obese
• Have diabetes or high blood pressure
• Have a history of inherited colorectal cancer
• Have few or no children
• Have a history of infertility, irregular menstrual periods or endometrial hyperplasia

Women taking the drug Tamoxifen to treat breast cancer are at a very slightly increased risk of endometrial cancer, however, this risk is outweighed by the benefit tamoxifen provides in preventing breast cancer.

Women who have taken contraceptive pills are only half as likely to develop the disease after menopause as those who have not.

The risk of endometrial cancer is linked to the amount of the female hormone oestrogen the endometrium has been exposed to during the woman's lifetime, since oestrogen stimulates cell formation. Women who have had a long span of menstruation have a higher risk of endometrial cancer.

Modern post-menopausal hormone replacement therapy (HRT) contains very low doses of oestrogen and progesterone, another female hormone that suppresses cell formation. Women using oestrogen only without progesterone have an increased risk of endometrial cancer. This is why oestrogen-only HRT is only recommended for those women who have had a hysterectomy.

Rare ovarian tumours can produce oestrogen and increase a woman’s chance of developing cancer of the uterus.

Being overweight increases the risk of endometrial cancer by three times, and being obese increases the risk by a factor of six. This is because being overweight and obese increases the amount of oestrogen in the body.

Can endometrial cancer be prevented?

In the majority of cases, endometrial cancer cannot be prevented. Staying healthy, eating well and watching your weight may help to reduce the risk of this cancer. You may also want to be supervised by a doctor to assess the risk of endometrial cancer when taking specific menopausal therapy.

If women need contraception, certain contraceptive pills can decrease the risk of endometrial cancer. It is important to stress that this should not be the primary use of the Pill and before making any decisions about contraception you should talk the pros and cons over with your doctor.

Many of the endometrial cancers develop over a period of several years, so early detection and evaluation of any abnormal postmenopausal bleeding may lead to an earlier diagnosis.