CDK4 and breast cancer: In the CDK4/6 inhibitor treatment cohort, high baseline NLR (>2.98) demonstrated significant association with shorter progression-free survival (PFS) and OS, which was confirmed by multivariate cox regression analysis [HR = 2.38, (95% CI: 1.23-4.6)], suggesting NLR could functions as a predictive marker for breast cancer patients receiving CDK4/6 inhibitor therapy (30).