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….randomly assigned (2:1) to the EVE arm (leuprorelin + LET + EVE) or the LET arm (leuprorelin + LET)...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)....EVE plus LET with ovarian-suppression resulted in longer PFS in tamoxifen-exposed HR+, HER2- metastatic breast cancer patients with visceral metastasis.