Changes in skeletal muscle and adipose tissue during cytotoxic chemotherapy for testicular germ cell carcinoma and associations with adverse events

• Multiagent chemotherapy is associated with a decline in skeletal muscle index, density, gauge, and an increase in fat mass index in patients with germ cell carcinoma of the testis undergoing chemotherapy. • Decreases in skeletal muscle measures are associated with an increased risk of chemotherapy-associated adverse events. • Neither baseline nor changes in adipose measures are associated with risk of chemotherapy-associated adverse events. To quantify changes in body composition during cytotoxic chemotherapy for germ cell carcinoma of the testis (GCT) and evaluate associations between change in skeletal muscle and adipose tissue and chemotherapy-associated adverse events. This retrospective single-institution study evaluated men with GCT treated with cytotoxic chemotherapy from 2005 to 2018. We measured skeletal muscle index (SMI [cm 2 /m 2 ]), skeletal muscle density (SMD [Hounsfield Units (HU)]), skeletal muscle gauge (SMG [cm²*HU/m²]), fat mass index (FMI [kg/m 2 ]), visceral adipose index (VAI [cm 2 /m 2 ]), and subcutaneous adipose index (SAI [cm 2 /m 2 ]) on axial computed tomography images at the level of the third lumbar vertebra within 75 days before and after chemotherapy. Chemotherapy-associated adverse events (AE) were graded based on the Common Terminology Criteria for Adverse Events (CTCAE v5.0.) Changes in body composition were quantified. Predictors of change in body composition were evaluated with multivariable linear regression. Associations between baseline or change in body composition and AEs were estimated with multivariable logistic regression adjusting for age, comorbidity, performance status, stage, and number/type of chemotherapy cycles. 141 patients (median age, 30 years [IQR 25-39]) including 86 patients (61%) with non-seminomatous GCT were included. Patients received a median of 3 cycles of cisplatin-based chemotherapy, and 124 patients (88%) completed planned chemotherapy. Median observed changes in SMI, SMD, and SMG were -6% ( P <0.0001), -2% ( P =0.07), and -7% ( P <0.0001), respectively, while FMI increased 5.3% ( P <0.0001). Overall, 120 patients (85%) experienced at least one AE including one or more ≥grade 3 AE in 57 patients (48%). Decrease in SMI (OR: 0.89, P =0.02), decrease in SMG (OR: 0.88, P =0.01,) and post-chemotherapy SMG (OR: 0.94, P =0.05) were independently associated with higher incidence of AEs, while pre-chemotherapy skeletal muscle parameters and post-chemotherapy SMI and SMD were not associated with AEs ( P >0.05 for all). Preoperative adipose tissue or change in adiposity was not associated with incidence of AEs. In men with GCT receiving cytotoxic chemotherapy, a decrease in skeletal muscle mass and quality during chemotherapy were associated with a higher incidence of chemotherapy-associated AEs. Adipose tissue was not associated with the incidence of AEs.