Endometriosis Ups Risk of Other Cancers

July 2, 2003 -- Women with endometriosis face an increased risk of ovarian and three other types of cancer, but they seem to have a lower risk of developing cervical cancer, according to a new Swedish study.

These findings, presented today at the annual meeting of the European Society for Human Reproduction and Embryology, also indicate a small increase in risk for non-Hodgkin's lymphoma, endocrine cancers, and brain tumors among women with endometriosis, a common gynecological condition that affects at least 5 1/2 million Americans and can cause infertility and pelvic pain. They also found that women with endometriosis who had undergone a hysterectomy had no higher rates of ovarian cancer.

"It is very important to keep these findings in perspective," researcher Anna-Sofia Berglund, MD, says in a prepared statement. "The overall risk of cancer does not increase after endometriosis, and where there are slightly increased risks, they are in some of the less common cancers."

Her findings result from reviewing records of women who had been discharged from a hospital with a diagnosis of endometriosis between 1969 and 2000 -- nearly 64,500 women. Their rates of cancer were then compared to all women listed in the National Swedish Cancer Register.

Berglund found that being diagnosed with endometriosis between ages 20 and 40 resulted in higher ovarian cancer rates than other age groups.

In the U.S., about 1 in 70 women will develop ovarian cancer during their lifetime, making it the most common of the four cancers in Berglund's study.

What Is Endometriosis?

Endometriosis affects between 7%-10% of all women and about 50% of premenopausal women, according to the American College of Obstetrics and Gynecology. Symptoms include painful cramps, heavy menstrual cycles, and pain during sex or during bowel movements; however, many women show no symptoms. It occurs when tissue that lines the inside of the uterus grows outside of it -- typically on the surface of organs in the pelvic and abdominal areas. Endometriosis can be treated with surgery or hormone therapy.

Michael Thun, MD, head of epidemiological research for the American Cancer Society, says that Berglund's finding is intriguing -- and possibly important -- for several reasons.

"For one thing, there's been surprisingly little epidemiologic study done on endometriosis, even though it's a condition that afflicts a lot of women," says Thun, who was not involved in the study.

"But from a scientific point of view, one of the interesting things about endometriosis is that it is non-malignant tissue than can invade other tissue -- it's tissue that is benign but behaves in a malignant way. Another interesting thing is that many aspects of endometriosis are like those of chronic inflammation, and there's a big interest in the relation of chronic inflammation and cancer."