Heterogeneity of Body Phenotype in Patients with Colorectal Cancer According to Therapeutic Strategy: A Cross-Sectional Observational Study

Background: Body composition may be a relevant determinant of metabolic and fun-ctional vulnerability in patients with colorectal cancer. This study aimed to investigate the association between different therapeutic strategies and body composition parameters. Methods: An observational, analytical, cross-sectional study was conducted in adult pa-tients with colorectal adenocarcinoma receiving active antineoplastic treatment at Hospital Universitario de Badajoz, Spain, consecutively recruited between November 2023 and June 2024. Nutritional status was assessed using the Patient-Generated Subjective Global Assessment (PG-SGA), and body composition was evaluated by multifrequency bio-electrical impedance analysis (BIA). Fat mass, fat-free mass, skeletal muscle mass, bone mass, protein mass, total body water, visceral fat, and basal metabolic rate were assessed. Patients were stratified according to treatment modality: surgery alone, FOREST protocol, neoadjuvant chemotherapy, adjuvant chemotherapy, and combined neoadju-vant-adjuvant chemotherapy. Between-group differences were assessed using ANOVA and association tests, complemented by regression models. Statistical significance was set at p< 0.05. Results: A total of 91 patients were included, with a mean age of 64.97±9.92 years; 56 (61.5%) were men. Significant differences between treatment modalities were observed in bone mass (p=0.023), protein mass (p=0.002), skeletal muscle mass (p=0.022), fat-free mass (p=0.022), and basal metabolic rate (p=0.039). Patients receiving adjuvant chemotherapy alone exhibited the lowest values for protein mass, skeletal muscle mass, fat-free mass, and basal metabolic rate, whereas those receiving combined neoadju-vant-adjuvant chemotherapy showed the highest values. No significant differences were observed in the remaining body composition parameters. Conclusions: Body composition differs significantly according to therapeutic modality, particularly in parameters related to skeletal muscle mass and physiological reserve. These findings support incorporating body composition assessment into comprehensive clinical and nutritional evaluation to identify patients with reduced physiological reserve and potentially greater treatment vulnerability. However, the cross-sectional design precludes causal inference. Prospective longitudinal studies are warranted to determine changes in body composition and their impact on treatment-related toxicity and clinical outcomes.