Association between the psoas muscle index and disease progression and mortality in testicular germ cell tumours

Background and objectives The relationship between sarcopenia and prognosis in patients undergoing chemotherapy for testicular germ cell tumours remains underexplored. We aimed to evaluate the impact of sarcopenia on disease progression and overall survival in these patients. Methods This retrospective multicentre study included patients who received chemotherapy for testicular germ cell tumours between January 2010 and December 2023. The psoas muscle index was calculated by measuring the cross-sectional area of the psoas muscle at the third lumbar vertebral level and was divided by the square of the height. Patients were divided into two groups based on changes in PMI (before and after chemotherapy): Group 1 (<10% change) and Group 2 (≥10% change). Results A total of 159 patients were analysed. Of these, 113 (71.1%) were in Group 1 and 46 (28.9%) in Group 2. Group 2 showed higher rates of disease progression (26.1% vs. 10.6%) and mortality (8.7% vs. 1.8%) (P=0.023 and P=0.038, respectively). In multivariable analysis, ≥10 % decrease in psoas muscle index [Hazard Ratio (HR)=6.499, P<0.001], rete testis invasion (HR=3.459, P=0.007), and non-seminomatous/mixed histology (HR=5.777, P=0.020) were identified as independent predictors of disease progression. For mortality, only a ≥10 % decrease in psoas muscle index was found to be a significant predictor (HR=5.994, P=0.049). Interpretation and conclusions A reduction in PMI is an independent prognostic factor for both disease progression and mortality in patients undergoing systemic chemotherapy for testicular germ cell tumours.