The use of nitrogenous bisphosphonates was associated with a nearly 50% reduction in the incidence of endometrial cancer among women in the PLCO, or Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial.
The endometrial cancer incidence rate among women in the study who reported ever using nitrogenous bisphosphonates was 8.7/10,000 person-years, compared with 17.7/10,000 person-years among those who reported never being exposed to nitrogenous bisphosphonates (rate ratio, 0.49), Sharon Hensley Alford, Ph.D., of the Henry Ford Health System, Detroit, and her colleagues reported online Dec. 22 in Cancer.
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The effect was similar after adjustment for age, race, body mass index, smoking status, and use of hormone therapy (hazard ratio, 0.56). The effect was also similar for both type I and type II disease, although there were only nine cases of type II disease, so the finding did not reach statistical significance, the investigators reported (Cancer 2014 Dec. 22 [doi:10.1002/cncr.28952]).
PLCO study subjects included in the current analysis were 23,485 women aged 55-74 years at study entry between 1993 and 2001, who had no cancer diagnosed prior to year 5 of the study when they completed a supplemental questionnaire to assess bone medication use. The women were followed until last known contact, death, or endometrial cancer diagnosis.
The findings support those of preclinical studies demonstrating antitumor effects of bisphosphonates, and suggest that their use may protect against endometrial cancer, the investigators said.
“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,” they concluded, adding that a trial assessing for endometrial, breast, and colorectal cancer in postmenopausal women would be ideal.
The PLCO trial was funded by the National Institutes of Health. The authors reported having no relevant financial disclosures.