Phase II trial with letrozole as neoadjuvant treatment in postmenopausal and premenopausal patients with highly endocrine responsive operable breast cancer.

Abstract

e12125 Background: Neoadjuvant endocrine therapy (NET)is effective in postmenopausal patients with breast cancers expressing oestrogen receptor. However, the therapeutic benefit of NET in premenopausal population is not fully characterized. We aimed to assess the efficacy and safety of endocrine therapy between the postmenopausal and premenopausal patients with highly endocrine responsiveoperable breast cancer for primary systemic therapy. Methods: Previously untreated patients with operable breast cancer and highly endocrine responsive breast cancer (ER/PR≥50% and Her2-) were recruited. Patients were assigned to receive letrozole 2.5mg daily (combined with triptorelin in premenopausal patients) for a period of at least 6 months. The primary end point of the study was the objective response rate (ORR) measured by breast ultrasound. Secondary end points included safety, pathologically complete response (pCR) rate, breast conservative surgery (BCS) rate. Results: Between September 2012 and December 2016, 41 patients were enrolled in the study (16 postmenopausal, 25 premenopausal ). The total ORR of this study was 73.2% (30 of 41). No significant differences were seen in the ORR, 76.0% (19 of 25 premenopausal patients) and 68.8% (11 of 16 postmenopausal patients) (P = 0.723). The pCR rate was 8% (2 of 25) for the premenopausal and 0%(0 of 16) for the postmenopausal (p=0.512). The BCS rate was 40% (10 of 25) for the premenopausal and 37.5%(6 of 16) for the postmenopausal (P = 0.873). No treatment-related grade 3/4 adverse events were recorded in both groups. Conclusions: Letrozole shows a high activity and excellent tolerability as neoadjuvant therapy in both postmenopausal and premenopausal patients with highly endocrine responsive operable breast cancer.