Summary
Crandall CJ, Aragaki AK, Cauley JA, et al. Breast tenderness and breast cancer risk in the estrogen plus progestin and estrogen-alone Women’s Health Initiative clinical trials. Breast Cancer Res Treat 2011 Nov 1. [Epub ahead of print] Level of evidence: I.
Researchers analyzed data from the Women’s Health Initiative estrogen plus progestin (N = 16,608, 5.6 y intervention) and estrogen-alone (N = 10,739, 6.8 y intervention) clinical trials. Participants underwent mammography and clinical breast exam at baseline and annually, with self-reported breast tenderness assessed at baseline and after 12 months. Medical record review confirmed invasive breast cancer.
Women assigned to active therapy rather than placebo had a significantly higher risk of new-onset breast tenderness after 12 months (conjugated equine estrogen [CEE]-alone vs placebo risk ratio [RR], 2.15; 95% CI, 1.97–2.35; CEE + medroxyprogesterone acetate [MPA] vs placebo RR, 3.07; 95% CI, 2.85-3.30). The risk of invasive breast cancer among women with baseline breast tenderness was doubled by CEE + MPA (hazard ratio [HR], 2.16; 95% CI, 1.29-3.74), but the effect was smaller in women without baseline breast tenderness (HR, 1.17; 95% CI, 0.97-1.41). There was an association between higher risk of breast cancer and new-onset breast tenderness among women using CEE + MPA (HR, 1.33; 95% CI, 1.02-1.72, P = 0.03), but not CEE-alone (HR, 0.98; 95% CI, 0.62-1.53).