CDK4 and breast cancer: Our study indicated that this novel therapeutic regimen achieved a pCR and RCB 0-I rate of 16.7%, while neoadjuvant therapies with combination of a CDK4/6 inhibitor and letrozole led to a pCR rate of 0–3.8% and RCB 0-I rate of 6.1–7.7% and treatment with NCT resulted in a pCR rate of 5.8–5.9% and RCB 0-I rate of 11.8–15.7% in HR-positive, HER2-negative breast cancer patients (Ma et al., 2017; Prat et al., 2020).