The Prognostic Significance of the NOLUS Score in Patients with Metastatic Breast Cancer Receiving CDK 4/6 Inhibitor Therapy

Vollständiger Abstract

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Aim: Breast cancer is the most common cancer, and in the metastatic hormone-positive group, CDK-4-6 inhibitors are used. We aimed to examine the prognostic value of the “NOLUS” score, calculated from the estrogen receptor (ER), progesterone receptor (PR), and Ki-67 index, in patients with breast cancer receiving CDK 4/6 inhibitors.Materials and Methods: This retrospective single-center study included 76 patients with HR+/HER2- metastatic breast cancer who were treated with CDK 4/6 inhibitors (ribociclib or palbociclib) and endocrine therapy between 2018 and 2024. The NOLUS score was calculated using the following formula: −0.45*ER% −0.28*PR% + 0.27*Ki67% + 73. A population-specific cutoff was determined via ROC analysis based on 2-year progression-free survival (PFS), classifying patients into “low-NOLUS” or “high-NOLUS” groups.Results: The median patient age was 58.2 years. Ribociclib and palbociclib were used in 78.9% and 21.1% of the patients, respectively. During a median follow-up of 38.4 months, no significant difference was observed in the median PFS between the low- and high-NOLUS groups (36.6 vs. 27.9 months; p=0.265). Similarly, 48-month overall survival (OS) rates were comparable (50.4% vs. 59.1%; p=0.772). Multivariate analysis revealed that palbociclib use was independently associated with a higher risk of progression than ribociclib use (HR, 2.12; p=0.026). ECOG performance status and Ki-67 index were identified as independent prognostic factors for OS.Conclusion: The NOLUS score was not a significant predictor of survival in patients with metastasis treated with CDK 4/6 inhibitors. However, this study provides real-world evidence regarding the differences in efficacy between CDK 4/6 inhibitors and highlights the prognostic value of ECOG status and Ki-67.