INFERTILITY AND NULLIPARITY AS RISK FACTORS FOR ENDOMETRIAL CANCER

NEW YORK (Reuters Health) - Infertility and nulliparity each contribute independently to endometrial cancer risk, new findings suggest.

Nulliparity has been linked to increased endometrial cancer risk in epidemiological studies, but many studies showing the association have not accounted for infertility, Dr. H.P. Yang of the National Cancer Institute in Bethesda, Maryland, and colleagues note in a report published March 3 in the British Journal of Cancer.

Also, they point out, there are many possible causes of infertility, and few studies have looked at endometrial cancer risk based on the cause of infertility.

To investigate, the researchers performed a pooled analysis of 8,153 cases and 11,713 controls from two cohort and 12 case-control studies. All information on infertility and infertility cause was self-reported, aside from one study using national registry data.

After adjusting for infertility, Dr. Yang and colleagues found that nulliparous women had significantly increased risk of endometrial cancer compared to parous women (odds ratio, 1.76).

Women who had problems with infertility had a 22% increase in the odds of endometrial cancer compared with women who did not. But when the researchers analyzed risk by specific infertility cause, none were associated with endometrial cancer.

Nulliparity could contribute to increased endometrial cancer risk because these women have a longer duration of estrogen exposure, the researchers write. The increased independent risk associated with nulliparity is higher than that linked to infertility, they add, which is consistent with other studies.

"Additional information about primary vs. secondary infertility might help clarify how infertility-associated endometrial cancer risk may vary by different parity categories as previous studies have reported differential risk for primary vs secondary infertility as it relates to endometrial cancer risk," the researchers add.

"Studies with large numbers of infertile and treated women, with improved measures of infertility parameters are needed," they conclude. "An international pooled analysis of data from large infertility clinics, which would have well-documented information about various parameters, including ages at pregnancies and infertility diagnosis and treatment modalities, is warranted."

SOURCE: http://bit.ly/1M5Swkf

Br J Cancer 2015;112:925-933.