Impact of Body Composition on Progression-Free Survival in Patients with Metastatic Breast Cancer Treated with Ribociclib.

Purpose: This study aims to determine whether body composition parameters affect progression-free survival (PFS) in patients with hormone receptor positive and HER-2 negative metastatic breast cancer treated with ribociclib as first-line therapy.

Materials and methods: It was designed as a single-center, retrospective study; therefore, its generalizability is limited. At the start of treatment, ¹⁸F-FDG PET/CT scans were performed on patients, and subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT) volume, SAT and VAT SUV (standardized uptake value) mean, SAT and VAT index, skeletal muscle index (SMI), and skeletal muscle radiodensity (SMD) were calculated at the L3 vertebra level. The albumin-myosteatosis gauge (AMG) was defined as SMD × albumin.

Results: The study included 73 participants. Increased SAT and VAT volumes were associated with worse PFS (23.4 vs. 35.5 months, p: 0.015; 25.4 vs. 33.3 months, p: 0.114). However, in the multivariable cox regression analysis for progression free survival (PFS), an increase in SAT volume [HR 4.96; p: 0.038)] and SAT SUV mean [HR 2.99; p: 0.016)] were identified as independent risk factors.

Conclusions: It should be noted that in patients treated with ribociclib, increases in SAT volume and SAT SUV mean are independent risk factors for PFS.