Longitudinal Changes in Nutritional, Inflammatory, and CT-Derived Body Composition Markers During Adjuvant Chemotherapy for Stage II/III Colorectal Cancer

Background/Objectives: Evidence on longitudinal changes in nutrition, inflammation, and body composition during adjuvant chemotherapy for Stage II/III colorectal cancer (CRC) remains limited. We therefore evaluated these changes and explored preoperative factors associated with treatment discontinuation and prognosis. Methods: This single-center retrospective study included patients with Stage II/III CRC who underwent curative surgery and adjuvant chemotherapy. Body mass index (BMI), computed tomography (CT)-derived psoas muscle index (PMI), psoas muscle density (PMD), modified intramuscular adipose tissue content (mIMAC), Geriatric Nutritional Risk Index (GNRI), Prognostic Nutritional Index (PNI), hemoglobin–albumin–lymphocyte–platelet (HALP) score, neutrophil-to-lymphocyte ratio (NLR), and platelet-to-lymphocyte ratio (PLR) were assessed preoperatively and 6 months after chemotherapy initiation. Analyses were stratified into oxaliplatin-based doublet therapy (CAPOX/FOLFOX) and fluoropyrimidine monotherapy. Results: Among 142 patients, GNRI, PNI, and HALP score increased, whereas BMI, NLR, and PLR decreased from preoperative assessment to follow-up. Adjuvant therapy was discontinued in 45 patients (31.7%). In the doublet therapy group, discontinuation was associated with lower preoperative GNRI, PNI, and HALP scores and higher NLR and PLR. In the monotherapy group, only older age was associated with discontinuation. Lower preoperative PMD and mIMAC, but not PMI, were associated with poorer overall survival. No other nutritional or inflammatory markers were associated with overall survival. Conclusions: Several nutritional and inflammatory markers improved from preoperative assessment to follow-up. Preoperative nutritional and inflammatory markers were associated with treatment discontinuation, particularly in the doublet therapy group. CT-derived muscle quality markers were associated with overall survival, suggesting prognostic relevance of muscle quality in this setting.