Oct. 27, 2011 -- Women who undergo ovarian stimulation as part of IVF (in vitro fertilization) treatment may be more likely to develop "borderline" ovarian tumors, but not invasive ovarian tumors, later in life, Dutch researchers report.
The researchers defined borderline ovarian tumors as low-grade ovarian cancer that is far less aggressive than invasive ovarian cancer.
The new study is published online in Human Reproduction. It's the first study to compare ovarian cancer rates among women with fertility problems who had gotten IVF and those who had not.
It's not yet clear if ovarian stimulation causes those borderline tumors, or if the risk applies to current IVF treatment.
Meanwhile, the researchers aren't calling for any changes in IVF use.
"We are talking about an increase in a special type of tumor that has an excellent prognosis," Flora van Leeuwen, PhD, a professor at The Netherlands Cancer Institute, tells WebMD. "The wish to have a child dominates the fear of a rare tumor that does not cause death."
Tracking Ovarian Tumors
The new study included more than 25,000 Dutch women who had been unable to conceive for at least one year. All but about 6,000 of them had undergone IVF treatment at least once between 1983 and 1995.
The women filled out surveys. The researchers also tracked the medical records of the women for 15 years, on average. During that time, women who had gotten IVF were twice as likely as the other women to develop any type of ovarian cancer -- particularly borderline ovarian tumors.
"Borderline tumors have low malignant potential. They are not what patients consider ovarian cancer. They are very different from 'real' ovarian cancer. That's a really important distinguishing factor," says Carolyn Runowicz, MD, a gynecologic oncologist and past president of the American Cancer Society. Runowicz was not involved with the Dutch study.
Borderline tumors do not spread to the surrounding tissue like invasive, or metastatic, cancers do. The tumors grow and must be surgically removed, but they would not require chemotherapy or lead to death, Runowicz tells WebMD.
Borderline tumors make up 15% to 30% of all ovarian cancers in the general population, according to the study. This was also true in the non-IVF group followed in the study. But in the IVF group, borderline tumors made up nearly 50% of the ovarian cancers.
Still, the odds of getting any type of ovarian cancer were low, even with IVF. The risk is similarly low in the U.S. Most U.S. women diagnosed with ovarian cancer are older than 60, and it accounts for only 3% of all women's cancers. About 12 in 100,000 women were diagnosed with ovarian cancer in the U.S. in 2006.
Never having children increases the risk for ovarian cancer, so women with fertility problems are already at greater risk. Researchers have questioned for some time whether IVF treatment increases that risk.
Role of IVF
There is still the possibility that something about fertility issues, rather than IVF treatment, makes women more likely to develop borderline ovarian tumors.
"You could easily reason that the ovaries of the women in the IVF group are more resistant to pregnancy than the other subfertile [women with fertility problems] group. It could be that there is some connection between severity of infertility and risk for a tumor," says Joe Leigh Simpson, MD, a gynecologist and past president of the American Society for Reproductive Medicine.
The results of the Dutch study are also based on IVF treatments used before 1995. Today's IVF treatments are different. "Enormous changes have occurred in the last 10-15 years. It's not necessary to stimulate women's ovaries as heavily as we did at one time," Simpson says.