Impact of Neoadjuvant Chemotherapy on Skeletal Muscle Mass in Colorectal Cancer Patients Undergoing Curative Surgical Resection: A Single-Centre Retrospective Observational Study

Background Neoadjuvant chemotherapy is often given before surgery in colorectal cancer to improve tumour resectability. However, its effects on skeletal muscle mass, which may influence post-operative recovery and functional outcomes, remain unclear. This study evaluates the impact of neoadjuvant chemotherapy on skeletal muscle mass in colorectal cancer patients undergoing curative surgery. Aim The aim of this study is to assess the effect of neoadjuvant chemotherapy on skeletal muscle mass in patients with colorectal cancer undergoing curative surgical resection. Methods A total of 100 patients who underwent surgical treatment for colorectal cancer between 2017 and 2022 were randomised into two groups: a chemotherapy group (n=50) that received neoadjuvant chemotherapy and a control group (n=50) that underwent surgery alone. Skeletal muscle area (cm²) was measured using CT scans both pre- and post-operatively: rectus abdominis at L1 and psoas at L4. Values were normalised for patient height squared to derive the skeletal muscle index (cm²/m²). Post-operative complications were recorded. Results The study enrolled 100 patients (median age 66.7 years, IQR 13.46; 58% male). No significant reduction in rectus or psoas muscle mass was observed pre- and post-chemotherapy in the treatment group (rectus: 4.33±3.8 vs. 4.03±1.96, p=0.567; psoas: 8.85±1.97 vs. 8.91±1.96; p=0.745). Baseline rectus muscle mass was comparable between groups (4.33±3.8 vs. 4.8±2.06; p=0.444). Post-operatively, the chemotherapy group showed lower rectus and psoas muscle mass compared to controls (rectus: 3.77±1.36 vs. 4.52±1.66, p=0.016; psoas: 9.09±1.93 vs. 10.13±2.86; p=0.037). No significant differences in pre- and post-treatment muscle mass change between groups (p>0.05). The chemotherapy group reported a higher incidence of falls (12% vs. 0%, p=0.027) and post-operative muscle weakness (22% vs. 0%, p=0.0004). Conclusion Neoadjuvant chemotherapy did not significantly impact short-term muscle mass loss in colorectal cancer patients undergoing curative surgery. However, a higher incidence of post-operative functional decline was observed, warranting further investigation.