Background: In renal cell carcinoma (RCC) and other solid organ malignancies, sarcopenia has been associated with decreased survival and increased perioperative complications. Traditional body composition analysis is an expensive and time extensive process. As a modifiable risk factor, more clinic friendly methods to identify patients with low muscle composition is of interest. Linear segmentation on routine imaging has been proposed as a fast, reliable and reproducible alternative. This study assesses the prognostic ability of linear segmentation in patients with nonmetastatic RCC. Methods: Patients that underwent nephrectomy for nonmetastatic RCC from 2005-2021 at an academic referral center were identified. Linear segmentation of the bilateral psoas/paraspinal muscles was completed on preoperative imaging obtained within 60 days of surgery. Cox proportional-hazards analysis was used to determine association between total muscle index and overall survival. Results: 532 (388 clear cell) patients were analyzed and a median total muscle index was 28.6 (25.8-32.5) for women and 33.3 (29.1-36.9) for men. As a binary variable, lower total muscle index was significantly associated with decreased survival in both the full (HR=1.96, 95% CI 1.32-2.90, p<0.001) and clear cell only cohorts (HR=1.78, 95% CI 1.08-2.75, p=0.022). As a continuous variable, unit increases in total muscle index were significantly associated with improved survival in the full cohort (HR=0.95, 95% CI 0.92-0.99, p=0.006) and the clear cell only cohort (HR=0.95, 95% CI 0.92-0.99, p=0.016). Conclusions: Assessment of muscle composition via linear segmentation on routinely obtained preoperative imaging is a clinically feasible technique with prognostic utility in patients with localized RCC. In this cohort of patients with nonmetastatic RCC, linear segmentation demonstrated significant associations with overall survival as a binary and continuous variable. This simplified technique may allow for routine inclusion of body composition into clinical decision making.

*Total Muscle Index=[Total Muscle Area]/height (m2). Other variables in model include age 60+, gender, race, obesity, ECOG, Nephrectomy type, T-Stage, N-Stage, grade, and histology.