Long or irregular menstrual cycles may be a signal of a woman’s risk for ovarian cancer, according to a recent study conducted by researchers at the Fred Hutchinson Cancer Research Center.
The study, which was published in the International Journal of Cancer, included 2041 women with epithelial ovarian cancer and 2100 controls to study whether menstrual cycle characteristics and self-reported polycystic ovary syndrome (PCOS) were related to ovarian cancer occurrence. Participants were interviewed about their menstrual cycle length, regularity or irregularity, and their PCOS status.
Results showed that there was no increase in ovarian cancer for women with regular menstrual cycles or with menstrual cycles that lasted over 35 days. Although there was no association between PCOS and ovarian cancer, researchers did find that there was a significant difference in the association between menstrual cycle irregularity and the risk of ovarian subtypes, as well as body mass index (BMI) and oral contraceptive (OC) use.
“Hormonal abnormalities among women with PCOS or menstrual cycle irregularity could be an explanation for the association observed in some studies,” Holly Harris, ScD, a researcher with the Fred Hutchinson Cancer Research Center in Seattle, said in an interview with Oncology Nursing News. “Conversely, there is also evidence that women who ovulate less frequently, which would be expected among women with long/irregular cycles, might have protection against ovarian cancer.” Harris added that women who take OCs have a reduced risk of ovarian cancer.
Harris explained that this study sought out to examine multiple subtypes of ovarian cancer because the term “ovarian cancer” actually describes what is thought to be multiple tumor types involving the ovary. Risk factors for each can vary.
Women who had irregular menstrual cycles saw a decreased risk of high-grade serous tumors, the most common type of ovarian cancer, but an increased risk of borderline serous tumors. However, the association between irregular menstrual cycles and serous borderline subtype was only statistically significant in women with irregular cycles who have never used OCs or were overweight, with a BMI at or above 25.
The study was not able to determine why risk levels differ when patients were stratified by BMI or OC use, so authors noted that the findings point toward the need for further research in the field.
“This observation may help us learn more about the different mechanisms that lead to the development of specific types of ovarian cancer,” Harris said. “Ovarian cancer is a rare cancer, so this study should not cause women to be overly concerned about their individual risk.” While most irregular menstrual cycles may not lead to cancer, it is important that a woman who is concerned about her periods see her healthcare provider, Harris explained.
“Future research in a larger collaborative study that includes more cases of ovarian cancer will help us clarify these associations, and that research is currently underway.”
Harris HR, Titus LJ, Cramer DW, Terry KL. Long and irregular menstrual cycles, polycystic ovary syndrome, and ovarian cancer risk in a population-based case-control study. Int J Cancer. 2017;140(2):285-291.