Linear Muscle Segmentation for Metastatic Renal Cell Carcinoma: Changes in Clinic-Friendly Estimation Predict Survival Following Cytoreductive Nephrectomy

Introduction Baseline sarcopenia and postoperative changes in muscle mass are independently associated with overall survival (OS) in patients with metastatic renal cell carcinoma (mRCC) undergoing cytoreductive nephrectomy (CN). Here we examine the relationships between preoperative (baseline), postoperative changes in muscle quantity, and survival outcomes following CN as determined by linear segmentation, a clinic-friendly tool that rapidly estimates muscle mass. Materials and Methods Our nephrectomy database was reviewed for patients with metastatic disease who underwent CN for RCC. Linear segmentation of the bilateral psoas/paraspinal muscles was completed for baseline imaging within 60 days of surgery and imaging 30 to 365 days postoperatively. Kruskal-Wallis for numerical and Fisher's exact test for categorical variables were used to test for differences between groups according to percent change in linear muscle index (LMI, cm2/m2). Multivariable Cox proportional hazards models evaluated associations between LMI percent change and cancer-specific (CSM) and all-cause mortality (ACM). Kaplan Meier curves estimated cancer-specific (CSS) and overall survival (OS). Results From 2004-2020, 205 patients were included of whom 52 demonstrated stable LMI (25.4%; LMI change < 5% [0Δ]), 60 increase (29.3%; LMI +5% [+Δ]), and 92 decrease (44.9%; LMI -5% [-Δ]). Median time from baseline imaging to surgery was 18 days, and time from surgery to postoperative imaging was 133 days. Median CSS and OS were highest among patients with 0Δ LMI (CSS: 133.6 [0Δ] vs. 61.9 [+Δ] vs. 37.4 [-Δ] months; P = .0018 || OS: 67.2 [0Δ] vs. 54.8 [+Δ] vs. 29.5 [-Δ] months; P = .0007). Stable LMI was a protective factor for CSM (HR 0.48; P = .024) and ACM (HR 0.59; P = .040) on multivariable analysis. Discussion Change in muscle mass after CN, as measured by the linear muscle segmentation technique, is independently associated with OS and CSS in patients following CN. Of note, lack of change was associated with longer survival.