What question did this study set out to answer?

This study evaluates the efficacy of neoadjuvant endocrine therapy combined with CDK4/6 inhibitors compared to chemotherapy in early HR+/HER2- breast cancer.

May 30, 2026

Chemotherapy-free neoadjuvant strategy in HR+/HER2− early breast cancer: Efficacy of CDK4/6 inhibitors plus endocrine therapy compared to chemotherapy-sequenced approach.

Key Points

This study evaluates the efficacy of neoadjuvant endocrine therapy combined with CDK4/6 inhibitors compared to chemotherapy in early HR+/HER2- breast cancer.
Retrospective analysis of 63 patients with HR+/HER2- breast cancer across 11 hospitals in China.
Comparison of two treatment groups: neoadjuvant endocrine therapy with CDK4/6 inhibitors (n=38) and chemotherapy followed by endocrine therapy with CDK4/6 inhibitors (n=25).
Statistical analyses included logistic regression and other tests to compare objective response rates.
Overall objective response rate (ORR) was 62%, with better responses in patients with Ki-67≤20% (67% vs. 58%).
No significant difference in ORR was found between the ET+CDK4/6i group (68%) and the chemotherapy group (52%) (OR: 0.41, 95% CI: 0.10–1.56; P=0.200).
Treatment was well-tolerated across groups, supporting chemotherapy-free options for selected patients.

Abstract

e12671 Background: In HR+/HER2- breast cancer (BC), neoadjuvant chemotherapy (NACT) remains a standard in many regions despite low pathological complete response (pCR) rates (7.5%–16.2%) and significant toxicity. The emergence of CDK4/6 inhibitors (CDK4/6i) has transformed management, with trials like CORALLEEN and WSG-ADAPT suggesting that neoadjuvant endocrine therapy (ET) plus CDK4/6i may offer comparable efficacy to NACT with improved tolerability. This study evaluates the feasibility of chemotherapy-sparing strategies by comparing the objective response rate (ORR) and safety of neoadjuvant ET+CDK4/6i versus NACT followed by ET+CDK4/6i in a real-world setting. Methods: We retrospectively analyzed 63 patients (aged 18–70 years) with HR+/HER2- BC across 11 tertiary hospitals in China. Patients were divided into two groups: those receiving neoadjuvant ET+CDK4/6i (n = 38; ribociclib, abemaciclib, dalpiciclib, or palbociclib) and those receiving NACT followed by ET+CDK4/6i (n = 25). ORR was defined by RECIST 1.1. Statistical analyses included Mann-Whitney U,X 2 , or Fisher’s exact tests, and logistic regression. Results: Baseline characteristics (age, Ki-67, T/N stage, and menopausal status) were well-balanced between groups ( P > 0.05). The overall ORR was 62%, with higher responses observed in patients with Ki-67≤20% (67%) compared to those with Ki-67 > 20% (58%). No significant difference in ORR was observed between the ET+CDK4/6i group (68%) and the chemo-sequenced group (52%) (OR: 0.41, 95% CI: 0.10–1.56; P = 0.200). In the Ki-67 > 20% subgroup, ET+CDK4/6i maintained a comparable ORR to the chemo-sequenced approach (63% vs. 53%, OR: 0.91, 95% CI: 0.64-1.29; P = 0.683). Among non-chemotherapy patients, ribociclib and abemaciclib showed similar efficacy (ORR 71% vs. 69%, OR: 1.07, 95% CI: 0.21-5.21; P = 0.936), while the dalpiciclib cohort achieved an ORR of 25% (n = 4, P = 0.121). Treatment was generally well-tolerated across cohorts. Conclusions: Neoadjuvant ET plus CDK4/6i achieves short-term ORR comparable to chemotherapy-sequenced regimens in HR+/HER2- early BC, even in patients with high Ki-67. These findings support the feasibility of chemotherapy-free neoadjuvant strategies for clinically selected patients, potentially mitigating toxicity without compromising initial treatment response.

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Cite This Study

Chen et al. (Thu,) studied this question.

synapsesocial.com/papers/6a1a81bf0307b78509433957 https://doi.org/https://doi.org/10.1200/jco.2026.44.16_suppl.e12671

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