Neoadjuvant Therapy of Cyclin-Dependent Kinase 4/6 Inhibitors Combined with Endocrine Therapy in HR+/HER2- Breast Cancer: A Systematic Review and Meta-Analysis

Background: Cyclin-dependent kinase (CDK) 4/6 inhibitors have been advocated for adjuvant therapy of metastatic hormone receptor (HR)+/human epidermal growth factor receptor 2 (HER2)- breast cancer (BC). However, the efficiency of adding CDK 4/6 inhibitors to neoadjuvant therapy was not unequivocal.

Objective: The aim of the study was to evaluate the efficiency and toxicity of neoadjuvant CDK 4/6 inhibitors + endocrine therapy (ET) versus neoadjuvant endocrine monotherapy or standard neoadjuvant chemotherapy in HR+/HER2- BC.

Method: We searched PubMed, the Cochrane Library, Web of Science, and Embase online databases for randomized controlled trials and single-arm studies written in English until April 2021.

Results: Five studies comparing CDK 4/6 inhibitors + ET as neoadjuvant treatments to ET alone and 2 studies comparing neoadjuvant CDK 4/6 inhibitors + ET to neoadjuvant chemotherapy were analysed. Neoadjuvant CDK 4/6 inhibitors + ET improved the rate of complete cell cycle arrest (CCCA: central Ki67 < 2.7%, odds ratio [OR] = 7.91, 95% confidence interval [CI] = 4.81-13.03, p < 0.001), increased the risk of adverse events (AEs; especially ≥3 AEs; AEs of all grades: OR = 9.10, 95% CI = 2.39-34.58, p = 0.001; AEs ≥3: OR = 12.24, 95% CI = 4.17-35.88, p < 0.001), led to no significant differences in pathological complete response (pCR) in patients with BC (OR = 0.34, 95% CI = 0.04-2.85, p = 0.318) compared to endocrine monotherapy. Moreover, subgroup analysis showed that the 3 types of CDK 4/6 inhibitors all improved the rate of CCCA (ribociclib: OR = 10.31, 95% CI = 3.59-29.61, p < 0.001; palbociclib: OR = 7.39, 95% CI = 1.26-43.40, p = 0.027, and abemaciclib: OR = 8.28, 95% CI = 3.41-20.11, p < 0.001). Compared to neoadjuvant chemotherapy, neoadjuvant CDK 4/6 inhibitors plus ET decreased the risk of AEs ≥3 (OR = 0.50, 95% CI = 0.29-0.87, p = 0.015) and showed similar ability to reach pCR (OR = 0.50, 95% CI = 0.12-2.07, p = 0.342) and reduce the residual cancer burden (RCB, RCB 0-1: OR = 0.47, 95% CI = 0.18-1.22, p = 0.121; RCB 2-3: OR = 2.30, 95% CI = 0.89-5.91, p = 0.084).

Conclusions: The results suggested that combination therapy had increased efficacy and toxicity compared to endocrine monotherapy and showed similar efficacy to and better safety than neoadjuvant chemotherapy.

Related Products

Cat.No.	Product Name	Information
S7440	Ribociclib	Ribociclib is an orally available, and highly specific inhibitor of CDK4 and CDK6 with IC50 of 10 nM and 39 nM. Phase 3.

Related Targets

CDK