FROM THE JOURNAL OF CLINICAL ONCOLOGY
A large prospective study found that among 89,918 women aged 50-79 years, bisphosphonate use was inversely associated with age-adjusted endometrial cancer risk, investigators reported. The study was published online Feb. 23 in the Journal of Clinical Oncology.
Crude incidence of endometrial cancer was 12 per 10,000 person-years for nonusers and 8 per 10,000 years for bisphosphonate users (bisphosphonate users: HR 0.76, 95% CI 0.61 to 0.94; P = .01). During the median 12.5-year follow up, 1,123 women (1,070 nonusers and 53 users) were diagnosed with endometrial cancer, reported Dr. Polly A. Newcomb and associates (J. Clin. Oncol. 2015 Feb. 23 [doi:10.1200/JCO.2014.58.6842]).
Bisphosphonate use was 2% at baseline and increased to 10% by year 6. It was treated as a time-varying never/ever variable that was updated at 1, 3, and 6 years. Compared with nonusers, bisphosphonate users were slightly older, leaner, more educated, and less likely to smoke.
This observational study is limited by the possibility of confounding factors. Women may have taken oral bisphosphonates because they had high fracture risk due to low endogenous estrogen from low weight, which is associated with low endometrial cancer risk. After the researchers controlled for weight and other confounding factors, such as fracture risk, the statistical analysis yielded similar measures of association (HR 0.80, 0.64 to 1.00; P = .05).
“In summary, our findings suggest that use of bisphosphonates is modestly associated with reduced endometrial cancer risk, a finding consistent with the inverse association between use of this medication and breast cancer risk,” wrote Dr. Newcomb of Fred Hutchinson Cancer and University of Washington Research Center, Seattle, and associates.
Dr. Newcomb and most coauthors had no disclosures. One coauthor reported consulting or advisory roles with Novartis, Pfizer, Genentech, Novo Nordisk, Genomic Health.
