Nitrogenous bisphosphonate use may reduce risk for endometrial cancer

Exposure to nitrogenous bisphosphonates appeared to have a protective effect on the incidence of endometrial cancer in women who never had the malignancy, according to study results.

“Other studies have shown that bisphosphonates may reduce the risk of certain cancers, but we are the first to show that the risk for endometrial cancer may also be reduced,” researcher Sharon Hensley Alford, PhD, of the Henry Ford Health System, said in a press release. “This study suggests that women who need bone strengthening medications and who have increased risk for endometrial cancer may want to choose the nitrogen form of bisphosphonates because this form may reduce the risk of endometrial cancer.”

Alford and colleagues reviewed data from 23,485 women without a cancer diagnosis who were enrolled in the Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial. About one-third (30%) of women were aged 65 to 69 years, and 92% were non-Hispanic white.

The women completed a supplemental questionnaire which included data on current or former nitrogenous bisphosphonate use during year 5 of the trial.

The analysis included data from 66,645 person-years of observation.

Overall, 97 cases of endometrial cancer occurred since the time of the questionnaire. Seventy-seven of these cases occurred among women who had never used bisphosphonates, whereas 20 occurred in bisphosphonate ever-users.

Researchers calculated a 0.48 (95% CI, 0.29-0.8) incidence rate ratio (IRR) for endometrial cancer among women who had used bisphosphonates. Data indicated these women had approximately one-half the risk for endometrial cancer as women who had not used bisphosphonates.

The risk for type I endometrial cancer also was significantly lower among bisphosphonate users (IRR=0.51; 95% CI, 0.31-0.86). However, the reduced risk for type II endometrial cancer did not reach statistical significance due to the low proportion of patients who had this disease type (IRR=0.23; 95% CI, 0.02-1.88).

In an analysis adjusted for age at study entry, race, BMI and use of hormone replacement therapy, the protective effect of bisphosphonate use persisted for all cases of endometrial cancer (HR=0.56; 95% CI, 0.34-0.93) and type I endometrial cancer (HR=0.58; 95% CI, 0.34-0.98).

“The results of the current study suggest that nitrogen-containing bisphosphonates may reduce the risk of endometrial cancer,” Alford and colleagues concluded. “However, additional studies are needed that include other potential confounders and a larger sample so that type II endometrial cancer could be assessed more confidently. A randomized trial in postmenopausal women that assessed endometrial, breast and colorectal cancer would be ideal.”

Disclosure: The researchers report no relevant financial disclosures.