BACKGROUND: Sarcopenia, characterized by loss of skeletal muscle mass and strength, is prevalent in patients undergoing treatment for colorectal cancer. Sarcopenia's prevalence in patients with cancer can reach up to 50% and is known to exacerbate postsurgical complications and affect long-term oncological outcomes. This study examined whether minimally invasive surgery (MIS) offers protective benefits against postoperative sarcopenia compared with open surgery in patients undergoing rectal cancer resection.

METHODS: This retrospective analysis included 145 patients who underwent open or minimally invasive (laparoscopic or robot-assisted) rectal resections at the University Hospital Dresden between 2013 and 2021. Confounding variables were adjusted using propensity score matching. The skeletal muscle index (SMI) and psoas muscle thickness per height (PMTH) were analysed in preoperative and postoperative computed tomography scans to measure changes in skeletal muscle mass. Potential risk factors for muscle loss were evaluated, and oncological long-term outcome was analysed.

RESULTS: The results indicate that oncological rectal resection did not result in pronounced postoperative muscle loss. No significant difference between the open and MIS groups in terms of postoperative muscle loss over 3 years postoperatively could be detected. Wound healing disorders were identified as the most significant independent risk factors for muscle loss (SMI loss > 10%). In contrast, neither the type of surgical technique nor the presence of a protective loop ileostomy significantly influenced the development of postoperative muscle loss. Patients who experienced a > 10% SMI loss within the first year had significantly poorer overall and disease-free survival. The 1-year survival rate was 93.3% in the group with high SMI loss compared with 100.0% in the group with low SMI loss (p = 0.435). The 3-year (66.7% vs. 95.6%, HR 8.75, 95% CI 1.855-41.286, p = 0.006) and 5-year (44.4% vs. 93.3%, HR 11.072, 95% CI 2.414-50.782, p = 0.002) survival rates were significantly lower in patients with high SMI loss. Patients with high SMI loss had an increased likelihood of recurrence and metastasis.

CONCLUSIONS: Although MIS did not confer a protective advantage against postoperative muscle loss in patients with rectal cancer, the findings highlight the critical role of maintaining muscle mass in improving survival outcomes. Postoperative muscle loss appears to be a marker of aggressive tumour behaviour, and interventions aimed at minimizing muscle loss, such as enhanced nutritional support, may improve the long-term patient prognosis. Future studies should explore interventional strategies to mitigate sarcopenia in this population.