Leuprorelin combined with letrozole with/without everolimus in ovarian-suppressed premenopausal women with hormone receptor-positive, HER2-negative metastatic breast cancer: The LEO study

Purpose: In the randomised phase II LEO trial, we investigated the effect of adding everolimus (EVE) to letrozole (LET) in ovarian-suppressed premenopausal women with hormone receptor-positive (HR+), HER2-negative (HER2-) recurrent/metastatic breast cancer. Methods: Patients with progression or prior exposure to tamoxifen with or without gonadotropin-releasing hormone agonists, either sequentially or concurrently, in adjuvant or metastatic setting were randomly assigned (2 : 1) to the EVE arm (leuprorelin + LET + EVE) or the LET arm (leuprorelin + LET) until disease progression or unacceptable toxicity. The primary end-point was progression-free survival (PFS). Secondary end-points included overall survival (OS), objective response rate (ORR), clinical benefit rate (CBR) and safety. Results: Between January 2014 and October 2018, 137 patients were enrolled (median age, 44 years [range, 24-56]). Of them, 75% had endocrine-sensitive disease, and 61% had visceral metastasis. With the median follow-up of 32.4 months, the median PFS was 18.1 months in the EVE arm and 13.8 months in the LET arm (HR 0.73, P = 0.137). Among patients with visceral metastases, the median PFS was significantly longer in the EVE arm (16.4 versus 9.5 months, P = 0.048). The median OS was not reached in both arms. The CBR was significantly higher in the EVE arm (83% versus 62%, P = 0.010). The ORR was similar between the two arms. The most common grade 3/4 adverse events in the EVE arm were neutropenia, alanine aminotransferase elevation and anaemia. Conclusions: EVE plus LET with ovarian-suppression resulted in longer PFS in tamoxifen-exposed HR+, HER2- metastatic breast cancer patients with visceral metastasis. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

This study showed that adding everolimus to letrozole with ovarian suppression can lead to longer progression-free survival in tamoxifen-exposed HR+, HER2- metastatic breast cancer patients, especially those with visceral metastasis.