Original Investigation

Bireociclib Plus Fulvestrant in Advanced Breast Cancer After Endocrine Progression

JAMA Oncology 10.1001/jamaoncol.2026.0318

March 19, 2026 at 11:00 AM EDT

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In hormone receptor (HR)–positive, human epidermal growth factor receptor 2 (; previously )–negative advanced breast cancer (ABC) after endocrine progression, does bireociclib improve outcomes?In this phase 3 randomized clinical trial including 305 patients, bireociclib plus fulvestrant prolonged median progression-free survival compared with placebo (14.7 months vs 7.3 months).In this trial, bireociclib with fulvestrant was a viable option for HR-positive, -negative ABC after endocrine progression.

Corresponding Author: Binghe Xu, MD, Department of Medical Oncology and State Key Laboratory of Molecular Oncology, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, No. 17 Panjiayuan St, Beijing 100021, China (xubh@cicams.ac.cn).

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