Longitudinal PET/CT-Derived Body Composition Changes During Systemic Therapy in Patients with Lung Cancer

Purpose: Host metabolic status may affect outcomes in lung cancer, but longitudinal changes in body composition and systemic metabolism remain incompletely understood. We examined whether paired 18F-FDG PET/CT-derived host features were associated with progression-free survival (PFS) during systemic therapy. Methods: Fifty-three patients with confirmed lung cancer who underwent baseline and post-treatment 18F-FDG PET/CT were retrospectively included. Tumor metabolic burden, body composition, organ metabolism, and brain metabolism were quantified. Delta values were defined as post-treatment minus baseline measurements. Associations with PFS were assessed using Kaplan–Meier analysis, adjusted Cox regression and exploratory metabolic network analysis. Results: During follow-up, 31 patients experienced disease progression, and median PFS was 7 months. SM volume (p = 0.001) decreased, and MedF volume (p < 0.001) increased at follow-up after FDR adjustment, whereas the numerical increases in SAT and TF volumes did not remain statistically significant after correction for multiple comparisons. Higher delta torso fat (TF) volume was associated with a lower risk of progression after adjustment (HR = 0.64, 95% CI: 0.43–0.97, p = 0.033). In the temporally aligned analysis of 29 patients whose follow-up PET/CT preceded progression, delta TF volume was not associated with subsequent PFS (HR, 1.84; 95% CI, 0.91–3.68; p = 0.087). Total network perturbation strength decreased after treatment (p = 0.002) but was not associated with PFS. Conclusions: Paired 18F-FDG PET/CT characterized longitudinal changes in body composition during systemic therapy. Delta TF volume showed an adjusted association with PFS in the exploratory full-cohort model, but its prognostic relevance requires further validation.