Myxofibrosarcoma (MFS) is a rare, aggressive soft tissue sarcoma with a high local recurrence rate, mostly affecting elderly patients. Sarcopenia, the progressive loss of skeletal muscle mass, and its CT-related assessment is an emerging prognostic factor in cancer care, yet its role in MFS remains unclear.

We conducted a retrospective longitudinal study of 55 patients with high-grade MFS who underwent surgical resection and had at least two CT scans between 2010 and 2024 with a mean scan-interval of 13.2 ± 2.1 months. CT-derived morphometric parameters, including skeletal muscle index (SMI), paraspinal muscle index (PSMI), psoas muscle index (PMI), skeletal muscle density (SMD), and visceral adipose tissue (VAT), were measured at the L3 vertebral level. We analyzed changes in body composition over time and their associations with chemotherapy, radiotherapy, tumor recurrence, postoperative complications, survival and functional status.

SMI, PSMI, PMI, and VAT declined significantly during the disease course, while SMD remained stable. Chemotherapy and local tumor recurrence were associated with greater muscle and fat loss, whereas radiotherapy showed no significant impact. A ≥ 15% decrease in SMI was associated with shorter median overall survival (32 vs. 80 months, p = 0.02). Although pre-treatment sarcopenia did not affect survival it was linked to longer hospital stays (p = 0.03) and increased risk for postoperative wound infections (p = 0.01).

CT-based body composition analysis offers a practical approach for risk stratification in MFS patients. Routine assessment of sarcopenia using existing imaging can help identify those at higher risk for poor survival, extended hospitalization, and wound complications. Incorporating these metrics into preoperative planning may guide early supportive measures, such as nutritional and wound care interventions. Prospective multicenter studies are needed to confirm these findings and assess whether targeted strategies can reduce sarcopenia-related morbidity and improve outcomes in this rare sarcoma.