Body Composition and Survival in Locally Advanced Rectal Cancer Patients Treated with Neoadjuvant Radiochemotherapy

<b>Background:</b> Nutritional status is a recognized determinant of treatment tolerance and clinical outcomes in oncology. This study aimed to assess body composition using computed tomography (CT) and to evaluate its association with progression-free survival (PFS) and overall survival (OS) in patients with locally advanced rectal cancer (LARC) undergoing curative multimodal therapy. <b>Methods:</b> A total of 216 patients with LARC who underwent neoadjuvant chemoradiotherapy (CRT) were retrospectively assessed. Two radiochemotherapy protocols were used: long-course chemoradiotherapy (lcCRT) (radiation therapy administered daily at doses of 1.8 or 2.0 Gy, for a total dose of 50.4-55.8 Gy) with concurrent chemotherapy: either 5-FU with leucovorin or capecitabine and total neoadjuvant chemoradiotherapy (tnCRT)-short-course radiotherapy (5 × 5 Gy) followed by sequential chemotherapy with CAPOX or FOLFOX. Surgery was performed 6.5 weeks after completing CRT. Radiotherapy was delivered using linear accelerators based on the Intensity-Modulated Radiation Therapy technique. CT scans were used to assess nutritional status. Survival analyses were performed. Data on food consumption frequency were collected using the Dietary Habits and Nutrition Beliefs Questionnaire (KomPAN^®). Non-Healthy-Diet-Index-14 (nHDI-14) was calculated. <b>Results:</b> Median observation time was 58 months (range 4-118 months). VATI level and OS (HR: 0.4618 95% CI: 0.2194-0.9719, <i>p</i> = 0.0419), as well as SATI and OS (HR: 0.4707 95% CI: 0.2286-0.9693, <i>p</i> = 0.0409) were significantly associated. This association was not significant for PFS (VATI: HR: 0.7084 95% CI: 0.4055-1.2376, <i>p</i> = 0.2259; SATI: HR: 0.6864 95% CI: 0.3932-1.1981, <i>p</i> = 0.1855). SMI and PMI values were not significantly related either PFS (SMI-HR: 0.6728, 95% CI: 0.4031-1.1231, <i>p</i> = 0.1295; PMI-HR: 0.7385, 95% CI: 0.4628-1.1785, <i>p</i> = 0.2036) or OS (SMI-HR: 0.9128, 95% CI: 0.4703-1.7720, <i>p</i> = 0.7876; PMI-HR: 0.6592 95% CI: 0.3684-1.1794, <i>p</i> = 0.1603). No significant association was found between sarcopenia development and PFS (HR: 1.2733 CI: 0.7589-2.1363; <i>p</i> = 0.3602) or OS (HR: 1.1207; CI: 0.5681-2.2107; <i>p</i> = 0.7424). Significant differences between men and women in alcohol intake and nHDI-14 were observed. <b>Conclusions:</b> Low visceral and subcutaneous adipose tissue index were significantly associated with worse OS in patients with LARC undergoing multimodal treatment. The nHDI-14 was negatively correlated with the duration of observation and patients' age.