SRS355 - Sarcopenia and outcomes in retroperitoneal and intra-abdominal sarcoma: a 10-year retrospective study

Abstract Introduction Assessment of sarcopenia has emerged as a prognostic indicator in several malignancies, including lung cancer, resectable colorectal cancer, and urological cancer (Suzuki et al., 2016; Yang et al., 2019; Li et al., 2019). These findings suggest sarcopenia may also serve as a prognostic marker in patients with retroperitoneal sarcoma, but evidence in this population is limited. Methods A retrospective analysis was conducted on patients diagnosed with sarcoma at a single trust over ten years (2014–2024). Psoas Muscle Index (PMI) was calculated from cross-sectional computed tomography (CT) imaging. Published PMI cut-offs (524 mm²/m² for males and 385 mm²/m² for females; Prado et al., 2008) were applied to identify sarcopenic patients. Mortality and cancer recurrence were the primary outcomes. To explore whether cohort-specific thresholds better predicted outcomes, sex-specific PMI cut-offs were also derived using receiver operating characteristic (ROC) analysis and Youden’s J statistic. Results Of 145 patients diagnosed with retroperitoneal or intra-abdominal sarcoma, six were excluded due to missing data, leaving 139 for analysis. 42 patients (30.2%) were sarcopenic and 97 (69.8%) non-sarcopenic. Mortality did not significantly differ between groups (23.8% versus 24.7%). Application of ROC/Youden’s J-derived thresholds did not meaningfully alter these findings. Recurrence rates were comparable (4.8% versus 3.1%). Discussion In this cohort, sarcopenia defined by PMI was not associated with increased mortality or recurrence in patients with retroperitoneal or intra-abdominal sarcoma. Further research incorporating more robust measures of skeletal muscle mass and function is required to clarify its prognostic value in this population.