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."
The finding didn't surprise Roberta B. Ness, MD, MPH, of the University of Pittsburgh Graduate School of Public Health. Last year, she presented her own research at the annual meeting of the Society of Gynecologic Oncologists suggesting that women with endometriosis did have an increased risk of ovarian cancer.
"This finding is not surprising at all," Ness tells WebMD. "The data continues to be very consistent: Overall, there's an increased risk of ovarian cancer in women who have endometriosis. And for women with longstanding endometriosis that is specifically affecting the ovaries -- that is, the abnormal cells are found on the ovarian surface -- the risk is even higher."
Because Berglund's study adds to previous evidence that hysterectomy seems to protect women with endometriosis against ovarian cancer, "I would say the more critical take-home message is that women who had hysterectomy had a reduction in (ovarian cancer) risk," says Ness, who is currently researching how women with endometriosis can reduce their cancer risk.
"We know there are things to reduce risk in women -- oral contraceptives, having babies, tubal ligation. What we don't know is, specifically, are these risks also preventative in women who have endometriosis?"