Study Explores Correlations Among Irregular Menstrual Cycles, PCOS, and Ovarian Cancer Risk

Long or irregular menstrual cycles may be a marker of an increased risk for developing certain subtypes of ovarian cancer, according to the results of a recent study published in the International Journal of Cancer.

The study evaluated menstrual cycle characteristics and self-reported polycystic ovary syndrome (PCOS) in 2041 women with epithelial ovarian cancer to see if any of these characteristics were related to ovarian cancer occurrence.

The results showed no elevation in ovarian cancer risk for women who reported periods that were never regular or for those reporting a menstrual cycle length of >35 days with odds ratios of 0.87 (95% CI&thinsp;=&thinsp;0.69-1.10) and 0.83 (95% CI&thinsp;=&thinsp;0.44-1.54), respectively. The researchers in this study also observed no overall association between self-reported PCOS and ovarian cancer (OR&thinsp;=&thinsp;0.97; 95% CI&thinsp;=&thinsp;0.61-1.56). However, the authors did find significant differences in the association between menstrual cycle irregularities and risk of ovarian cancer subtypes (p_{heterogeneity} &thinsp;=&thinsp;0.03) as well as by body mass index (BMI) and oral contraceptive (OC) use (p_interaction &thinsp;<&thinsp;0.01).

Menstrual cycle irregularity was also found to be associated with a decreased risk of high grade serous tumors, and at the same time, correlated with an increased risk of serous borderline tumors among women who had never used OCs and those who were overweight.

However, the association between irregular menstrual cycles and serous borderline subtype was only shown to be statistically significant in patients with irregular cycles who have never used OCs or were overweight, with a BMI >25.

“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 OncLive. “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 explained that this study was meant to examine multiple subtypes of ovarian cancer because the term “ovarian cancer” actually encompasses what is thought to be multiple tumor types involving the ovary. Moreover, risk factors for each subtype can vary.

This research was not able to determine why risk levels differ when patients are stratified by BMI or OC use. Thus, the study authors noted that their findings highlight 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.

Harris went on to say that a larger collaborative study that includes more cases of ovarian cancer would help to 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.