Postoperative loss of skeletal muscle mass and visceral fat predicts survival and morbidity after surgically treated non-metastatic chondrosarcoma: a longitudinal CT morphometric study.

backgroundChondrosarcoma is the second most common malignant primary bone tumor in adults. Surgical resection is the mainstay of treatment. However, outcomes remain heterogeneous even after complete (R0) resection within its oncologic margins. The prognostic relevance of CT-based body composition, both preoperatively and over the disease course, has not been defined in chondrosarcoma.

methodsA retrospective cohort study including 79 adults with histologically confirmed, non-metastatic (N0M0) chondrosarcoma treated by complete (R0) resection between 2010 and 2024 was conducted. Each patient had two evaluable CT examinations acquired on the same scanner, a preoperative baseline (tCT1) and a follow-up scan approximately one year postoperatively (tCT2; mean interval 13.3 ± 2.2 months). At the L3 level, skeletal muscle and visceral fat indices (Skeletal muscle index (SMI), Paraspinal Muscle Index (PSMI), Psoas Muscle Index (PMI), Skeletal Muscle Density (SMD), Visceral adipose Tissue (VAT)) were derived and compared over time. Changes were analyzed in relation to tumor localization and grade. Survival was assessed using Kaplan-Meier and Cox regression models. ROC analysis/Youden J Index identified prognostic thresholds (SMI loss ≥ 30%; VAT loss ≥ 25%). Preoperative sarcopenia was defined using established sex-specific SMI cutoffs.

resultsA marked postoperative deterioration in SMI, PSMI, PMI, and VAT was observed, whereas muscle density (SMD) largely remained unchanged. Losses were most pronounced in trunk-localized tumors (e.g., SMI - 41.3 ± 20.4%) and in high-grade disease (SMI: G1 - 22.5 ± 13.2%, G2 - 36.3 ± 20.6%, G3 - 52.1 ± 15.6%). Patients with SMI loss ≥ 30% showed reduced median overall survival (64 vs. 116 months; p = 0.02), and VAT loss ≥ 25% was associated with similarly poor survival (42 vs. 88 months; p < 0.01). In multivariable analysis, both SMI loss ≥ 30% (HR 1.44, 95% CI 1.10-2.33; p = 0.02) and VAT loss ≥ 25% (HR 1.40, 95% CI 1.20-2.41; p = 0.01) independently predicted worse survival. Preoperative sarcopenia was associated with shorter median survival (42 vs. 116 months; p < 0.0001), higher surgical site infection rates (27% vs. 2%; p < 0.001), and prolonged hospitalization across anatomical sites (all p < 0.001), and remained an independent prognostic factor on adjusted analysis (HR 1.31, 95% CI 1.19-2.45; p < 0.01).

conclusionsIn R0-resected, non-metastatic chondrosarcoma, both preoperative sarcopenia and postoperative declines in muscle and adipose tissue, particularly SMI loss ≥ 30% and VAT loss ≥ 25%, are independent predictors of reduced survival and worse postoperative outcomes. Leveraging routinely acquired staging CTs for morphometric analysis may enable early risk identification and guide personalized perioperative management.