Women who receive ovarian stimulation for assisted reproductive technology (ART) procedures don’t have an increased risk of developing ovarian cancer when compared to subfertile women who don’t undergo ART, according to a new study.
The results suggest that nulliparity is likely responsible for the increased risk of ovarian cancer observed in patients treated with ART, the researchers said.
Earlier, shorter studies had only compared ART-treated women with women from the general population.
“Subfertile women differ from women in the general population according to several ovarian cancer risk factors. Therefore, to estimate the risk of ovarian cancer associated with ART, it was important to include a comparison group of women who were subfertile and not treated with ART,” said senior study author Flora E. van Leeuwen, PhD, of Netherlands Cancer Institute in Amsterdam.
She and her colleagues conducted a nationwide cohort study of 30,625 women who received ovarian stimulation for ART during 1983-2000 and 9,988 women who received fertility treatments other than ART.
Incident invasive and borderline ovarian tumors were ascertained through linkage with the Netherlands Cancer Registry and the Dutch Pathology Registry. Ovarian tumor risk in ART-treated women was compared with risks in the general population and the subfertile non-ART group.
The researchers reported the results in the Journal of the National Cancer Institute.
Risk of ovarian cancer
Women treated with ART were no more likely to develop ovarian cancer than subfertile women not treated with ART (adjusted hazard ratio, 1.02), but the ART group did have an increased risk of ovarian cancer when compared to the general population (standardized incidence ratio, 1.43).
“This, however, turned out to be due to the fact that the women who had received ART were less likely to have children. Not having children is a known risk factor for ovarian cancer,” Dr. van Leeuwen said.
Women with more ART procedures that resulted in the birth of a child were at lower risk of developing ovarian cancer, compared with women without any successful cycle (Ptrend = .001). However, women who had only cycles not resulting in a birth were not at higher risk of ovarian cancer when they had a greater number of cycles.
“These results indicate that parity decreases the risk of ovarian cancer, also in ART-treated women. But more unsuccessful ART cycles do not increase the risk of ovarian cancer,” Dr. van Leeuwen said.
Risk of borderline ovarian tumors
The risk of developing borderline ovarian tumors was roughly twice as high in women who had received ART, both compared with women who had received other fertility treatments (hazard ratio, 1.84) and women from the general population (standardized incidence ratio, 2.20).
However, the risk of developing borderline ovarian tumors did not increase in women who had received multiple ART procedures.
“If there was a causal association between ART and increased risk of borderline ovarian tumors, we would expect to see this risk increase with a greater number of ART procedures from more hormones and more stimulation of the ovaries. This makes the direct link between ART and increased risk of borderline tumors a bit uncertain. It might be caused by other factors, such as the severity of infertility,” Dr. van Leeuwen said.
Borderline ovarian tumors are rare in the general population in the Netherlands, and women who develop these tumors generally have a good prognosis, she said.
The risk of developing a borderline tumor before the age of 55 for women in the Netherlands is approximately 0.2%. After ART, the study found a risk of approximately 0.3%.