Increasing adipose burden in young men with metastatic testicular cancer following front-line cytotoxic chemotherapy

525 Background: Exposure to cytotoxic chemotherapy (CC) has been observed to be associated with significant changes in body composition, namely marked lean muscle mass losses, with implications for treatment-related toxicity and oncologic outcomes. However, prior studies predominately include elderly patients who, a priori, are at risk for sarcopenia or severe skeletal muscle deficiency. To date, the impact of CC on body composition in young men with testicular cancer remains undefined. Methods: A retrospective analysis of 19 patients with metastatic testicular cancer treated with CC was performed (2015-17). Lumbar skeletal muscle index (SMI), visceral (VAI), subcutaneous (SCAI), and intramuscular adipose (IMAI) indices (cm2/m2), as well as fat-free mass (FFM, kg) and fat mass (FM, kg) were calculated using cross-sectional soft tissue area measurements on pre- and post-CC computed tomography (CT) axial scans and compared using paired Wilcoxon Signed Rank Tests. Results: Median age was 29 years. According to the NHANES FMI-based classification, 5 (26.3%), 9 (47.4%), 4 (21.1%), and 1 (5.3%) patients had normal, excess, class I, and class II obesity, respectively. Median pre- and post-CC BMI was 27.7 vs. 29.6 kg/m2(p = 0.03). Median pre- and post-CC SMI, VAI, SAI, and IAI were 63.5 vs 57.8 (p = 0.14), 19.9 vs 30.8 (p = 0.01), 47.9 vs 58.2 (p = 0.03), and 3.0 vs 5.2 (p = 0.002), respectively. Median muscle density pre- and post-CC were 47.0 vs 43.6 HU (p = 0.002). Pre- and post-chemotherapy FFM were 21.5 vs 19.5 kg, representing an overall median loss of 2.8%, (IQR -10.1, +4.7; Range -49.5 - +16.3; p = 0.14). Conversely, pre- and post-CC FM were 6.6 vs 7.5 kg, representing an overall median gain of 13.3% (IQR -3.3, +17.0; -24.9 - +50; p = 0.01). Median time between imaging assessments was 121 days. Specific median measures of adiposity each increased significantly, such that VIA increased by 29% (p = 0.01), SCAI increased by 39.7% (p = 0.03), and IMIA increased by 39.7% (p = 0.002). Conclusions: While lean muscularity remained stable, we observed significant increases in total body adipose mass with decreased muscle density in this consecutive case series of testicular cancer patients following CC.