Letrozole as Neoadjuvant Treatment in Postmenopausal and Premenopausal Patients With Highly Endocrine Responsive Operable Breast Cancer

Estrogen receptor (ER) positive constitutes about 75% of all breast cancer(BC). Neoadjuvant endocrine therapy(NET) plays an important part in primary therapy of the hormone receptor (HR) -positive and HER2 -negative breast cancer. Recent studies revealed that the third-generation aromatase inhibitors (AIs) have superior ORR than tamoxifen in the HR-positive BC post-menopausal patients. The Z1031 trial showed that Letrozole obtained better ORR than the other two AIs anastrozole and exemestane after 16-18 weeks NET, although without any statistically significance.

In spite of these findings, the optimal duration of NET has not been fully elaborated, Although prolonged treatment might further reduce the tumor size. Further clinical benefits were achieved when the period of treatment of neoadjuvant letrozole prolonged more than three to four months. The 2015 St. Gallen International Consensus Conference recommended continuing neoadjuvant therapy in highly hormone-sensitive breast cancer for a minimum of 4-8 months. However, most studies aim to identify the excellent efficacy of the AIs compared with other drugs but not the duration of NET therapy. Antonio et al. suggest that the time to maximum clinical efficacy may be the optimal period of treatment for the patients; And the median time to maximum efficacy was 4.2 months (95% CI, 4.0-4.5). The present study evaluated the time to CR/PR and the ORR after 6 months of NET.

Previous clinical studies investigating NET mainly focused on post-menopausal women, data on pre-menopausal women is still relatively lacking due to the widely perception that more benefit may be achieved from neoadjuvant chemotherapy (NCT) among younger patients. The result of Z1031 trial showed superiority of neoadjuvant of AIs and promoted wider application of AIs as NET in the HR-positive post-menopausal women, and the clinical response rate (CRR) of letrozole was 74.8% after 16-18 weeks of treatment. The combination of AIs and GnRH analogue may be alternative for selected pre-menopausal patients. The STAGE trial showed the overall response rates of anastrozole plus goserelin in pre-menopausal patients was 70.4% after 6 months of NET. However, studies comparing the ORR and optimal duration of NET between pre-menopausal and post-menopausal patients were rare.

The purpose of the our research was to compare the duration to CR/PR and the ORR after 6 months of NET between pre-menopausal and post-menopausal women with highly endocrine responsive operable BC.