<b>Methods:</b> A Markov chain Monte Carlo simulation model estimated the costs and benefits of 3 extended endocrine strategies in a hypothetical cohort of premenopausal women with ER-positive early breast cancer: (1) no further treatment; (2) tamoxifen for 5 years (extended tamoxifen); or (3) OA/AI for 5 years.
<b>Purpose:</b> Estrogen receptor-positive (ER<sup>+</sup>) breast cancers are typically treated with endocrine agents, and dependence on the ER pathway is often retained even after multiple rounds of antiestrogen therapy.
<b>Purpose:</b> Antiendocrine therapy remains the most effective treatment for estrogen receptor-positive (ER<sup>+</sup>) breast cancer, but development of resistance is a major clinical complication.
<b>Purpose:</b> As estrogen receptor-positive (ER<sup>+</sup>) breast cancer in <i>BRCA1</i> mutation carriers arises at an older age with less aggressive tumor characteristics than ER-negative (ER<sup>-</sup>) <i>BRCA1</i>-mutated breast cancer, it has been suggested that these tumors are "sporadic" and not <i>BRCA1</i> driven.
<b>Purpose:</b> In breast cancer models, combination epigenetic therapy with a DNA methyltransferase inhibitor and a histone deacetylase inhibitor led to reexpression of genes encoding important therapeutic targets, including the estrogen receptor (ER).
<b>Purpose:</b> Steroidal androgens suppress androgen receptor and estrogen receptor positive (AR/ER<sup>+</sup>) breast cancer cells and were used to treat breast cancer, eliciting favorable response.
<b>Purpose:</b> This study aimed to identify biomarkers of resistance to endocrine therapy in estrogen receptor-positive (ER<sup>+</sup>) breast cancers treated with prolonged neoadjuvant letrozole.<b>Experimental Design:</b> We performed targeted DNA and RNA sequencing in 68 ER<sup>+</sup> breast cancers from patients treated with preoperative letrozole (median, 7 months).<b>Results:</b> Twenty-four tumors (35%) exhibited a PEPI score ≥4 and/or recurred after a median of 58 months and were considered endocrine resistant.
<sup>18</sup>F-FES and <sup>18</sup>F-FDG PET/CT imaging in vivo revealed that ERα expression in DIS-ZR751 treated with fulvestrant, and tumor activity in DIS-ZR751 treated with combination drugs decreased as early as 7 days after treatment.