Abstract：
OBJECTIVE: Human epidermal growth factor receptor 2 (HER2)-low breast cancer (BC) is a new entity considered a biologically distinct subtype from HER2-zero BC. However, the importance of HER2 low expression on the activity of cyclin-dependent kinase 4/6 inhibitor (CDK4/6i) remains unclear.
METHODS: We conducted a single-center retrospective study including hormone receptor-positive (HR +) /HER2- metastatic BC (mBC) patients treated with CDK4/6i plus endocrine treatment (ET) as first-line therapy. Clinical outcomes were analyzed according to HER2 expression.
RESULTS: 258 women were analyzed with a median follow-up of 25.4 months; 39.9% had HER2 low, and 60.1% had HER2 zero BC. Median progression-free survival (mPFS) in the HER2-low group was 27.6 months compared with 44.3 months in the HER2-zero group (p = 0.341). In patients receiving ribociclib, the mPFS in the HER2-low group was 24.2 months compared with 53.1 months in the HER2-zero group (multivariate-adjusted HR: 1.981, 95 Cl 1.094-3.586; p = 0.024). The survival probabilities at 24, 36 and 48 months for the HER2 low and HER2 zero groups were 82%, 69%, 69% and 83%, 75% and 69%, respectively (p = 0.336). Objective response rate (p = 0.179) and disease control rate (p = 0.338) did not significantly differ between HER-2-low and HER-2-zero groups.
CONCLUSIONS: The mPFS in the Her2-zero group was almost twice that of the Her2-low group, but the difference was not statistically significant. mPFS was significantly longer in the HER2-zero group compared to the HER2-low group in patients receiving ribociclib. More prospective studies are needed to understand the actual consequences of this biomarker.
METHODS: We conducted a single-center retrospective study including hormone receptor-positive (HR +) /HER2- metastatic BC (mBC) patients treated with CDK4/6i plus endocrine treatment (ET) as first-line therapy. Clinical outcomes were analyzed according to HER2 expression.
RESULTS: 258 women were analyzed with a median follow-up of 25.4 months; 39.9% had HER2 low, and 60.1% had HER2 zero BC. Median progression-free survival (mPFS) in the HER2-low group was 27.6 months compared with 44.3 months in the HER2-zero group (p = 0.341). In patients receiving ribociclib, the mPFS in the HER2-low group was 24.2 months compared with 53.1 months in the HER2-zero group (multivariate-adjusted HR: 1.981, 95 Cl 1.094-3.586; p = 0.024). The survival probabilities at 24, 36 and 48 months for the HER2 low and HER2 zero groups were 82%, 69%, 69% and 83%, 75% and 69%, respectively (p = 0.336). Objective response rate (p = 0.179) and disease control rate (p = 0.338) did not significantly differ between HER-2-low and HER-2-zero groups.
CONCLUSIONS: The mPFS in the Her2-zero group was almost twice that of the Her2-low group, but the difference was not statistically significant. mPFS was significantly longer in the HER2-zero group compared to the HER2-low group in patients receiving ribociclib. More prospective studies are needed to understand the actual consequences of this biomarker.
摘要：
目的：人类表皮生长因子受体2（HER2）-低乳腺癌（BC）是一种新实体，被认为是与HER2-零BC生物学上不同的亚型。然而,HER2低表达对细胞周期蛋白依赖性激酶4/6抑制剂(CDK4/6i)活性的重要性尚不清楚.
方法：我们进行了一项单中心回顾性研究，包括接受CDK4/6i联合内分泌治疗（ET）作为一线治疗的激素受体阳性（HR+）/HER2-转移性BC（mBC）患者。根据HER2表达分析临床结果。
结果：258名女性接受了分析，中位随访时间为25.4个月；39.9%的患者HER2低，60.1%有HER2零BC。HER2低组的中位无进展生存期（mPFS）为27.6个月，而HER2零组为44.3个月（p=0.341）。在接受瑞博西尼治疗的患者中，HER2低组的mPFS为24.2个月,HER2零组为53.1个月(多变量校正HR:1.981,95Cl1.094-3.586;p=0.024).HER2低组和HER2零组在24、36和48个月的生存概率为82%。69%,69%和83%，75%和69%，分别(p=0.336)。HER-2低组和HER-2零组之间的客观反应率（p=0.179）和疾病控制率（p=0.338）没有显着差异。
结论：Her2零组的mPFS几乎是Her2低组的两倍，但差异无统计学意义。在接受ribociclib的患者中，与HER2低组相比，HER2零组的mPFS明显更长。需要更多的前瞻性研究来了解这种生物标志物的实际后果。
方法：我们进行了一项单中心回顾性研究，包括接受CDK4/6i联合内分泌治疗（ET）作为一线治疗的激素受体阳性（HR+）/HER2-转移性BC（mBC）患者。根据HER2表达分析临床结果。
结果：258名女性接受了分析，中位随访时间为25.4个月；39.9%的患者HER2低，60.1%有HER2零BC。HER2低组的中位无进展生存期（mPFS）为27.6个月，而HER2零组为44.3个月（p=0.341）。在接受瑞博西尼治疗的患者中，HER2低组的mPFS为24.2个月,HER2零组为53.1个月(多变量校正HR:1.981,95Cl1.094-3.586;p=0.024).HER2低组和HER2零组在24、36和48个月的生存概率为82%。69%,69%和83%，75%和69%，分别(p=0.336)。HER-2低组和HER-2零组之间的客观反应率（p=0.179）和疾病控制率（p=0.338）没有显着差异。
结论：Her2零组的mPFS几乎是Her2低组的两倍，但差异无统计学意义。在接受ribociclib的患者中，与HER2低组相比，HER2零组的mPFS明显更长。需要更多的前瞻性研究来了解这种生物标志物的实际后果。
