CEE + MPA doubles the risk of breast cancer in women with baseline breast tenderness
TUESDAY, Nov. 22 (HealthDay News) -- For women, use of conjugated equine estrogen (CEE) and medroxyprogesterone (MPA) is associated with new-onset breast tenderness, which correlates with increased breast cancer risk, according to a study published online Nov. 1 in Breast Cancer Research and Treatment.
Carolyn J. Crandall, M.D., from the University of California in Los Angeles, and colleagues investigated the association between breast tenderness and breast cancer risk among women taking CEE alone or in combination with MPA therapy. Data were analyzed for women enrolled in the Women's Health Initiative trials, which included 16,608 women on combination therapy and 10,739 women taking estrogen alone. Mammography and clinical breast examinations were performed at baseline and annually, and self-reported breast tenderness was assessed at baseline and at 12 months.
The investigators found that women assigned to active therapy had a significantly increased risk of new-onset breast tenderness after 12 months compared with those assigned to placebo (CEE alone versus placebo risk ratio [RR], 2.15; CEE + MPA versus placebo RR, 3.07). For women with baseline breast tenderness, CEE + MPA was associated with a significantly increased risk of invasive breast cancer (hazard ratio [HR], 2.16); whereas the effect was smaller for women without baseline breast tenderness (HR, 1.17; 95 percent confidence interval [CI], 0.97 to 1.41). New-onset tenderness during active treatment correlated with increased breast cancer risk for women taking CEE + MPA (HR, 1.33), but not for women taking CEE alone (HR, 0.98; 95 percent CI, 0.62 to 1.53).
"New-onset breast tenderness during use of CEE + MPA was associated with increased subsequent breast cancer risk," the authors write.
Two authors disclosed financial ties to the pharmaceutical industry. One author provided expert testimony on behalf of the Fred Hutchinson Cancer Research Center.