The standard therapy for hormone-receptor-positive, human epidermal growth factor receptor 2-negative advanced breast cancer includes the use of cyclin-dependent kinase 4/6 inhibitors (CDK4/6i) with endocrine therapy. The optimal post-CDK4/6i treatment sequence is unclear. This cohort study evaluated the initiation, characteristics, and outcomes of chemotherapy following CDK4/6i-based treatment. Among the 227 patients who began CDK4/6i therapy, 114 completed it. Seventy-nine female patients received further treatment, including 55 receiving chemotherapy. The average age was 60.1 years. Post-CDK4/6i chemotherapy was typically (69.1%) first-line due to an impending visceral crisis. The median progression-free survival (mPFS) was 3.0 months (range 0.5–18.9), and the median overall survival (mOS) was 8.3 months (0.5–26.1). The median OS from the end of CDK4/6i treatment was 12.4 months (1.5–26.8). In univariate analysis, neither mPFS nor mOS was associated with age, tumor grade, receptor status, Ki67 status, time from diagnosis to CDK4/6i cessation, therapy line, or CDK4/6i type. Dose reduction occurred in 12 patients (21.8%), and chemotherapy was ceased due to adverse events in 8 patients (14.6%). Chemotherapy showed limited benefit regardless of the regimen. The role of chemotherapy may evolve with broader CDK4/6i use in adjuvant treatment.
激素受体阳性、人表皮生长因子受体2阴性晚期乳腺癌的标准治疗方案包括使用细胞周期蛋白依赖性激酶4/6抑制剂联合内分泌治疗。目前尚不明确CDK4/6抑制剂治疗后的最佳后续治疗方案。本队列研究评估了基于CDK4/6抑制剂治疗后化疗的启动时机、患者特征及临床结局。在开始CDK4/6抑制剂治疗的227例患者中，114例完成治疗。79例女性患者接受了后续治疗，其中55例接受化疗。患者平均年龄为60.1岁。因面临内脏危象风险，69.1%的患者将CDK4/6抑制剂治疗后化疗作为一线方案。中位无进展生存期为3.0个月（范围0.5-18.9），中位总生存期为8.3个月（0.5-26.1）。自CDK4/6抑制剂治疗结束后的中位总生存期为12.4个月（1.5-26.8）。单变量分析显示，中位无进展生存期和中位总生存期与年龄、肿瘤分级、受体状态、Ki67状态、从确诊至停用CDK4/6抑制剂的时间、治疗线数或CDK4/6抑制剂类型均无显著关联。12例患者（21.8%）需要降低化疗剂量，8例患者（14.6%）因不良事件终止化疗。无论采用何种化疗方案，其临床获益均有限。随着CDK4/6抑制剂在辅助治疗中的广泛应用，化疗的作用定位可能发生演变。
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