Evaluation of the relationship between body composition and local response to neoadjuvant therapy in patients with locally advanced rectal carcinoma

Gundogdu, M. Evaluation of the Relationship Between Body Composition and Local Response to Neoadjuvant Therapy in Patients with Locally Advanced Rectal Carcinoma, Eskişehir Osmangazi University, Faculty of Medicine, Department of Radiology, Medical Specialization Thesis, Eskişehir, 2025. The aim of this study is to evaluate the relationship between body composition parameters and treatment response following neoadjuvant chemoradiotherapy in patients with locally advanced rectal cancer. This retrospective study included 67 patients diagnosed between 2015 and 2024 with complete imaging data. Body composition measurements obtained at the level of the L3 vertebra using computed tomography included psoas muscle area (PMA), skeletal muscle area (SMA), visceral and subcutaneous adipose tissue areas (VAT, SAT), and mean skeletal muscle radiodensity (MSMR). PMA was indexed to height to calculate the psoas muscle index (PMI). Based on these parameters, patients were grouped as sarcopenic or non-sarcopenic according to PMI; with or without myosteatosis according to MSMR; and low or high visceral adipose tissue area according to VAT. Treatment response was assessed using magnetic resonance imaging-based tumor regression grade (mrTRG) and categorized into good and poor response groups. The visceral adipose tissue area was found to be significantly higher in the poor response group (p=0.042). No significant correlation was found between other body composition parameters and treatment response. The results suggest that visceral adiposity may serve as an independent predictor of treatment response and that body composition analysis may have potential prognostic value in the pre-treatment evaluation. Key Words: Rectal cancer, neoadjuvant therapy, visceral adipose tissue, sarcopenia, body composition