RT Journal Article SR Electronic T1 Clinical Trial of Acolbifene in Premenopausal Women at High Risk for Breast Cancer JF Cancer Prevention Research JO Cancer Prev Res (Phila) FD American Association for Cancer Research SP 1146 OP 1155 DO 10.1158/1940-6207.CAPR-15-0109 VO 8 IS 12 A1 Fabian, Carol J. A1 Kimler, Bruce F. A1 Zalles, Carola M. A1 Phillips, Teresa A. A1 Metheny, Trina A1 Petroff, Brian K. A1 Havighurst, Thomas C. A1 Kim, KyungMann A1 Bailey, Howard H. A1 Heckman-Stoddard, Brandy M. YR 2015 UL http://cancerpreventionresearch.aacrjournals.org/content/8/12/1146.abstract AB The purpose of this study was to assess the feasibility of using the selective estrogen receptor modulator (SERM) acolbifene as a breast cancer prevention agent in premenopausal women. To do so, we assessed change in proliferation in benign breast tissue sampled by random periareolar fine-needle aspiration (RPFNA) as a primary endpoint, along with changes in other risk biomarkers and objective and subjective side effects as secondary endpoints. Twenty-five women with cytologic hyperplasia ± atypia and ≥2% of breast epithelial cells staining positive for Ki-67, received 20 mg acolbifene daily for 6–8 months, and then had benign breast tissue and blood risk biomarkers reassessed. Ki-67 decreased from a median of 4.6% [interquartile range (IQR), 3.1%–8.5%] at baseline to 1.4% (IQR, 0.6%–3.5%) after acolbifene (P < 0.001; Wilcoxon signed-rank test), despite increases in bioavailable estradiol. There were also significant decreases in expression (RT-qPCR) of estrogen-inducible genes that code for pS2, ERα, and progesterone receptor (P ≤ 0.026). There was no significant change in serum IGF1, IGFBP3, IGF1:IGFBP3 ratio, or mammographic breast density. Subjective side effects were minimal with no significant increase in hot flashes, muscle cramps, arthralgias, or fatigue. Objective measures showed a clinically insignificant decrease in lumbar spine bone density (DEXA) and an increase in ovarian cysts but no change in endometrial thickness (sonography). In summary, acolbifene was associated with favorable changes in benign breast epithelial cell proliferation and estrogen-inducible gene expression but minimal side effects, suggesting a phase IIB placebo-controlled trial evaluating it further for breast cancer prevention. Cancer Prev Res; 8(12); 1146–55. ©2015 AACR.