According to a new study by researchers in the U.S., oral contraceptives and intrauterine devices (IUD) appear to provide long-term protection against endometrial cancer.

The researchers, led by Dr. Xiao Ou Shu of Vanderbilt University, Nashville, Tennessee conducted a study of 1,204 women from Shanghai with newly diagnosed endometrial cancer and compared them to 1,212 healthy women.

The women were matched according to various characteristics.

The endometrium is the lining of the uterus, or womb and endometrial cancer involves a cancerous growth in that area which mainly occurs after menopause and causes vaginal bleeding.

A hysterectomy (surgical removal of the uterus) is generally performed to treat the disease.

It is the most common gynecologic cancer in the United States, and over 35,000 women are diagnosed with it each year.

Effective screening has meant it is now the third most common cause of gynecologic cancer deaths (behind ovarian and cervical cancer).

Endometrial cancer is often referred to as uterine cancer, however the uterus may harbor other malignancies, including cervical cancer, sarcoma, and trophoblastic disease.

The team found that overall, 223 of the cancer patients (18.5 percent) and 302 of the controls (24.9 percent) reported using an oral contraceptive.

After accounting for other known risk factors or protective factors for endometrial cancer, the use of oral contraceptives was associated with a 25 percent reduced risk.

That risk decreased with long-term use and after 72 months, the cancer risk was reduced by 50 percent.

This protective effect was maintained, even 25 years or longer after oral contraceptives were discontinued.

IUD use was associated with a 47 percent lower risk of endometrial cancer and the duration of IUD use, and age when it was first and last use did not significantly alter the association.

The researchers suggest that the progestin component of oral contraceptives may help reduce the overgrowth of cell in the endometrium, while the protective effect of IUDs may be prompted by “inflammatory actions” that eliminate abnormal and precancerous endometrial cells.

The study is published in the International Journal of Cancer, November 2006.