DENVER — Even long-term use of oral contraceptives can't nullify the substantially increased risk of endometrial cancer conferred by obesity, results of a case-control study show.
“These results highlight the importance of weight reduction in the primary prevention of endometrial cancer,” Dr. Linda S. Cook observed at the annual meeting of the American Association for Cancer Research.
She presented a study of OC use in 542 endometrial cancer patients enrolled in the population-based Alberta, Canada, cancer registry during a recent 3-year period, as well as in 1,032 randomly selected age-matched controls.
As other studies have shown, OC use protected against endometrial cancer. The benefit was duration dependent. Women who used OCs for less than 5 years had an adjusted 26% reduction in endometrial cancer risk relative to never-users, and women with a history of 5 years or more of OC use had a 43% risk reduction after adjustment for age, body mass index (BMI), parity, menopausal status, and urban versus rural residence, reported Dr. Cook of the University of New Mexico, Albuquerque.
What's new in this study are the findings on how a history of OC use interacts with parity and BMI to affect endometrial cancer risk. Increasing parity and OC use reduced risk in what appeared to be additive fashion. For example, women with a parity of three or more plus a history of at least 5 years on OCs had an 83% reduction in risk of endometrial cancer compared with nulliparous non-OC users. On the other hand, endometrial cancer risk climbed with increasing BMI. Overweight women had a greater risk than normal-weight women, and obese women had a higher risk than overweight ones. Even with a history of at least 5 years of OC use, obese women still had a 2.8-fold greater risk of the malignancy than normal-weight non-OC users.