In breast cancer presurgical trials, the Ki-67 labeling index predicts disease outcome and offers clues to the preventive potential of drugs. We conducted a placebo-controlled trial to evaluate the activity of exemestane and celecoxib before surgery. The main endpoint was the change in Ki-67. Secondary endpoints were the modulation of circulating biomarkers. Postmenopausal women with histologically confirmed estrogen receptor-positive breast cancer were randomly assigned to exemestane 25 mg/day (n = 50), or celecoxib 800 mg/day (n = 50), or placebo (n = 25) for 6 weeks before surgery. Changes in biomarkers were analyzed through an ANCOVA model adjusting for baseline values. Exemestane showed a median absolute 10% reduction in Ki-67 [from 22 (interquartile range, IQR, 16-27), to 8 (IQR 5-18)], and a 15% absolute reduction in PgR expression [from 50 (IQR 3-90) to 15 (IQR -0-30)] after 6 weeks of treatment. Exemestane significantly increased testosterone [median change 0.21 ng/mL, (IQR 0.12-0.35)], decreased SHBG [median change -14.6 nmol/L, (IQR -23.1 to -8.6)], decreased total and HDL cholesterol by -10 mg/dL (IQR -21-2) and -7 mg/dL, (IQR -14 to -2), respectively. Triglycerides were reduced by both agents [median change -0.5 mg/dL (IQR -17.5-13.5) and -8 mg/dL (IQR -28-9) for celecoxib and exemestane, respectively]. Exemestane showed a remarkable antiproliferative effect on breast cancer, whereas celecoxib did not affect breast cancer proliferation. Given the proven preventive efficacy of exemestane, these findings support the use of Ki-67 to explore the optimal exemestane dose and schedule in the prevention setting. Cancer Prev Res; 9(5); 349-56. ©2016 AACR.
©2016 American Association for Cancer Research.