Abstract
BACKGROUND/AIM: Accumulating evidence suggests that muscle mass depletion (sarcopenia) has a negative impact on survival in several malignancies, including biliary tract cancer (BTC). Computed tomography (CT)-measured psoas muscle thickness to height ratio (PMTH) has been reported as a surrogate measure for muscle mass that does not require specialized equipment or software. The aim of this retrospective study was to investigate whether preoperative PMTH predicts oncological outcomes of patients undergoing surgical resection for BTC. PATIENTS AND METHODS: PMTH was assessed in 211 patients by analyzing axial CT images at the level of the umbilicus. The most predictive cutoff of PMTH was determined by survival classification and regression tree analysis. Propensity score-based inverse probability weighting (IPW) was used to balance characteristics between the low and high PMTH groups. RESULTS: Applying a PMTH cutoff of 17.5 mm/m, the low PMTH group comprised 114 patients (54%). Low PMTH was associated with female sex, non-obesity, CA19-9 elevation, and lymph node metastasis. After IPW adjustment, the low PMTH group had a significantly shorter disease-specific survival (p<0.001) and relapse-free survival (p<0.001) than the high PMTH group. IPW-adjusted regression analysis revealed that a low PMTH was independently associated with worse disease-specific survival (hazard ratio=2.98, p<0.001) and relapse-free survival (hazard ratio=2.49, p<0.001), in addition to other factors such as tumor differentiation, perineural invasion, and resection margin status. CONCLUSION: Preoperative PMTH may be a simple and feasible index of sarcopenia for predicting poor survival after resection of BTC.