Relationship between overall survival and progression-free survival with 18 F-FDG PET/CT metabolic parameters in metastatic breast cancer patients treated with CDK 4/6 inhibitors

BACKGROUND: Combining CDK 4/6 inhibitors with endocrine therapy (ET) extends progression-free survival (PFS) and overall survival (OS) in hormone receptor (HR) positive, human epidermal growth factor receptor-2 (HER2) negative metastatic breast cancer. We aimed to explore the relationship between metabolic tumor volume (MTV), total lesion glycolysis (TLG), and PFS/OS in these patients. METHODS: MTV and TLG were measured from baseline 18 F-fluorodeoxyglucose (18-FDG) positron emission tomography/computed tomography (PET/CT) of 87 HR-positive/HER2-negative metastatic breast cancer patients and their effects on survival were analyzed using Kaplan-Meier methods. RESULTS: (p = 0.001). The median OS was 40.3 months for patients with TLG < 732.4 g and 24.6 months with ≥ 732.4 g (p = 0.006). The median OS for patients with an ECOG score of 0 was 53.6 months, while for those with an ECOG score of 1-2, it was 26.4 months (p = 0.005). Age ≥ 60 years (HR = 5.11, p = 0.002) and ECOG score > 0 (HR = 3.38, p = 0.011) are independent predictors of PFS. CONCLUSIONS: Baseline 18 F-FDG PET/CT may provide prognostic insights in HR+/HER2- metastatic breast cancer. High MTV and TLG are associated with poorer OS in univariate analyses but not in multivariable analyses. ECOG score > 0 and age ≥ 60 years are independent predictors of PFS.