Preoperative endocrine therapy for HER2-negative hormone receptor–positive breast cancer

Preoperative endocrine therapy may be an option for postmenopausal women with hormone receptor–positive breast cancer when chemotherapy is not a suitable option because of comorbidities or performance status. Although the toxicity profile of preoperative hormonal therapy over the course of 3 to 6 months is favorable, the pCR rates obtained (1%–8%) are far lower than have been reported with chemotherapy in unselected populations.[18][Level of evidence B3]

Longer duration of preoperative therapy may be required in this patient population. Preoperative tamoxifen was associated with an overall response rate of 33%, with maximum response occurring up to 12 months after therapy in some patients.[19] A randomized study of 4, 8, or 12 months of preoperative letrozole in older patients who were not fit for chemotherapy indicated that the longer duration of therapy resulted in the highest pCR rate (17.5% vs. 5% vs. 2.5%, P-value for trend < .04).[20][Level of evidence B3]

Aromatase inhibitors (AIs) have also been compared with tamoxifen in the preoperative setting. Overall objective response and breast-conserving therapy rates with 3 to 4 months of preoperative therapy were either statistically significantly improved in the AI-treated women [18] or comparable to tamoxifen-associated outcomes.[20]

The use of preoperative endocrine therapy in premenopausal women with hormone-responsive breast cancer remains investigational.