4196 - Ribociclib (RIBO) + letrozole (LET) in male patients (pts) with hormone receptor-positive (HR+), human epidermal growth factor receptor-2–negative (HER2–) advanced breast cancer (ABC) and no prior endocrine therapy (ET) for ABC: Preliminary subgroup results from the phase 3b CompLEEment-1 trial

Background

CDK4/6 inhibitor RIBO is approved for use in combination with an aromatase inhibitor for the treatment of HR+, HER2– ABC in postmenopausal women with no prior therapy for ABC, based on the significantly prolonged progression-free survival versus placebo + LET observed in the pivotal phase 3 MONALEESA-2 trial (Hortobagyi et al. NEJM 2016). However, relatively rare pt subsets such as men with HR+, HER2– ABC were not included in that trial. Here, we report early safety results for men enrolled in CompLEEment-1, an open-label, phase 3b trial evaluating RIBO+LET as first-line therapy in an expanded pt population.

Methods

Pts with HR+, HER2– ABC, ≤1 line of prior chemotherapy, and no prior ET for ABC received RIBO (600 mg/day, 3 wk on/1 wk off) + LET (2.5 mg/day); men and premenopausal women received concomitant goserelin (3.6-mg subcutaneous implant every 28 days). The primary outcome was safety and tolerability. A pre-planned interim analysis was conducted ~15 months after first pt first visit.

Results

Of the first 1,008 pts enrolled who completed 56 days of follow-up or discontinued before the data cut-off, 20 were men. Median age was 63.5 years and all had an Eastern Cooperative Oncology Group performance status ≤1; 45.0% had stage IV disease at diagnosis. The most common sites of metastasis were lung (75.0%), lymph nodes (40.0%), and liver (20.0%). The most frequent adverse events (AEs) were hot flush (30.0%), neutropenia (20.0%), and constipation (20.0%). Grade ≥3 AEs included neutropenia (4 pts, 20.0%), increased alanine aminotransferase (2 pts, 10.0%), and increased aspartate aminotransferase (1 pt, 5.0%). QT prolongation was infrequent, occurring in 3 (15.0%) men; all events were grade 1/2. Dose reduction or interruption due to AEs occurred in 35.0% of men; 2 discontinued treatment due to AEs.

Conclusions

Preliminary results from the CompLEEment-1 study demonstrate the safety and tolerability of first-line RIBO+LET+goserelin in male pts, consistent with previous reports in female pts. NCT02941926.

Clinical trial identification

NCT02941926

Editorial Acknowledgement

Financial support for medical editorial assistance was provided by Novartis Pharmaceuticals. We thank Holly C. Cappelli, PhD, ProEd Communications, Inc., for her medical editorial assistance with this abstract.