Ribociclib plus letrozole was found safe and effective for the treatment of hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2−) advanced breast cancer in men. These findings were published in Breast Cancer Research and Treatment.

Men historically have not been included in clinical trials for breast cancer; however, due to the increasing prevalence of breast cancer in men, the United States Food and Drug Administration (FDA) now recommends including men in trials.

The Compleement-1 trial was a single-arm, open-label, multicenter phase 3b study of ribociclib plus letrozole for the treatment of HR+ HER2− advanced breast cancer conducted between 2016 and 2018 and included 3246 patients. For this analysis, data from the 39 men who participated in the trial were evaluated for safety and efficacy.

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The men in this study were median age 62.0 years (range, 33 to 80), 71.8% were White, and 46.2% had an Eastern Cooperative Oncology Group (ECOG) performance score of 1-2.

Most men reported adverse events (97.4%) and treatment-related events (92.3%). Only one male patient reported a serious treatment-related event. Four male patients discontinued treatment due to adverse events, 28 had dose adjustment or interruption due to adverse events, and 30 experienced an event requiring additional therapy.

Neutropenia occurred in 53.8% of male patients, and was grade 3 or higher in 41.0%.

Observed trends in safety and tolerability were similar across the all patients and male patients cohorts.

The overall response (46.9% vs 43.6%), clinical benefit (71.9% vs 69.1%), partial response (43.8% vs 40.9%), and complete response (3.1% vs 2.7%) rates were similar in the all male patients and all patients cohorts, respectively.

This analysis was not prespecified in the trial design.

These data indicate that men with HR+ HER2− advanced breast cancer had similar safety and efficacy profiles as all patients treated with ribociclib plus letrozole.

Disclosure: Some authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of disclosures.


Campone M, De Laurentiis M, Zamagni C, et al. Ribociclib plus letrozole in male patients with hormone receptor‑positive, human epidermal growth factor receptor 2‑negative advanced breast cancer: subgroup analysis of the phase IIIb CompLEEment‑1 trial. Breast Cancer Res Treat. 2022;193(1):95-103. doi:10.1007/s10549-022-06543-1