This study of 1128 women with a mismatch repair gene mutation, 133 of whom were diagnosed with endometrial cancer, reports a protective effect for use of hormonal contraceptives, a later age at menarche and increased parity. The directions of these associations are similar to those reported for the general population, suggesting a possible protective effect of these factors. The authors say that if their findings are replicated, women with a mismatch repair gene mutation may be counselled like the general population in regard to hormonal influences on endometrial cancer risk.
Two other factors that have been associated with endometrial cancer risk in the general population that were not observed in this study include age at menopause and postmenopausal hormone use. The authors note however that most of the women in their cohort were premenopausal (and hence low use of postmenopausal hormones), therefore the study may have lacked statistical power to identify any associations with these variables (unmeasured confounding or information bias may also account for this).
The authors discuss a previous small randomised trial which found oral contraceptive pills or medroxyprogesterone acetate were associated with decreased endometrial proliferation in women with a known mismatch repair gene mutation or a history of Lynch syndrome–associated cancer. They say their findings provide further evidence to support the hypothesis that long-term exposure to hormonal contraceptives may significantly reduce the risk of endometrial cancer in Lynch syndrome. They do however acknowledge the various limitations of their study, mainly those inherent to its retrospective nature.