Associations of psoas muscle index and inflammatory markers with FDG PET/CT-derived metabolic response after total neoadjuvant therapy in locally advanced rectal cancer

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Objective: Total neoadjuvant therapy (TNT) is increasingly used for locally advanced rectal cancer, but factors associated with metabolic tumor response remain unclear. This study aimed to explore correlations between fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT)-derived metabolic tumor response and patient-related factors, including body composition, systemic inflammatory markers, and imaging-based biomarkers, in patients receiving TNT. Materials and Methods: This retrospective single-center study included 15 patients with locally advanced rectal cancer who underwent baseline and post-treatment FDG PET/CT imaging. Metabolic tumor parameters, including maximum standardized uptake value (SUVmax), standardized uptake value normalized to lean body mass mean (SULmean), total lesion glycolysis (TLG), and metabolic tumor volume (MTV), were extracted, and percentage changes were calculated. Psoas muscle area, psoas muscle index (PMI), and subcutaneous fat were measured from the CT component, while spleen-to-liver ratio (SLR), liver-to-rectus femoris ratio (LRF), and laboratory inflammatory indices, including neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), albumin, and C-reactive protein (CRP), were assessed as host-related variables. Results: Significant reductions were observed in all metabolic PET/CT parameters after treatment. Psoas muscle area and PMI showed significant negative correlations with percentage changes in all four metabolic parameters, with correlation coefficients ranging from −0.614 to −0.879, suggesting that higher psoas-derived muscle measurements may be associated with greater metabolic reduction after treatment. Albumin change was significantly correlated with TLG and MTV response. In contrast, NLR, PLR, CRP, and subcutaneous fat showed no significant associations with metabolic tumor response. The SLR correlated modestly with MTV change only. Conclusion: Baseline psoas-derived muscle measurements, particularly PMI, may be associated with metabolic tumor response after TNT in locally advanced rectal cancer. These findings should be considered preliminary and hypothesis-generating and may support further evaluation of body composition assessment during pre-treatment evaluation of this patient population.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.