Neoadjuvant endocrine therapy in primary breast cancer.

Neoadjuvant chemotherapy has been employed increasingly in operable breast cancer during recent years. Several randomized trials showed that the chances of breast conserving therapy are being enhanced, and that survival was not compromised by primary systemic therapy compared to adjuvant treatment. Apart from the surgical advantages of tumor downstaging and breast conservation, therapy upfront might offer the chance to predict subsequent response of an individual patient to a given agent in the adjuvant setting. Furthermore, by investigating pre- and posttreatment tumor specimens, the neaodjuvant setting might help to evaluate new predictive biological markers, assess biologic effects of new treatments, and gain insight into molecular mechanisms. For postmenopausal patients with receptor-positive disease who cannot tolerate the toxicities of chemotherapy regimens or are not eligible for immediate surgery, endocrine treatment is emerging as an attractive alternative in the neoadjuvant setting. The new third-generation aromatase inhibitors letrozole and anastrozole have been compared to tamoxifen in 3 well-designed randomized neoadjuvant phase III trials (PO24, IMPACT, and PROACT). These studies showed significantly higher response rates for letrozole than for tamoxifen, and comparable ones for anastrozole. Thus, the primary use of an aromatase inhibitor seems a feasible and safe treatment option for postmenopausal women with early-stage breast cancer who do not wish to or are unable to undergo immediate surgery or preoperative chemotherapy. Further neoadjuvant endocrine trials should help us to elucidate the cross-talk between the different signal transduction pathways and their role in endocrine resistance.