Prediction of Everolimus Toxicity and Prognostic Value of Skeletal Muscle Index in Patients With Metastatic Renal Cell Carcinoma

Abstract Background The objective of the study was to assess the prognostic role of skeletal muscle index (SMI) in metastatic renal cell carcinoma (mRCC) patients treated with everolimus, and its effect of on everolimus-induced toxicity. Patients and Methods Consecutive mRCC patients treated with everolimus between February 2007 and November 2014 underwent computed tomography scans at a single center performed by the same radiologist. SMI was assessed before everolimus treatment using the L3 cross-sectional area. Overall survival (OS) was analyzed according to SMI value. Results were adjusted using the International Metastatic Database Consortium (IMDC) prognostic group, body mass index (BMI), and/or number of previous tyrosine kinase inhibitor lines (NPL). Results One hundred twenty-four mRCC patients (mean age, 60.21 years) were treated with everolimus as second- or third-line (82.3%) or > third-line (17.7%) therapy. Most patients (87.9%) had clear cell carcinoma. IMDC prognostic group was “favorable” (32.3%), “intermediate” (50%), or “poor” (17.7%). Median SMI was 40.75. OS was longer in patients from the highest versus lowest SMI tercile: 21.9 versus 10 months ( P  = .002). Continuous SMI at baseline was not significantly associated with OS after adjustment for IMDC prognostic group, BMI, or NPL but the highest versus lowest SMI tercile was an independent prognostic factor in multivariate analysis ( P  = .025). There was no difference in everolimus toxicity between SMI tercile groups. Conclusion SMI was an independent prognostic factor for mRCC patients treated with everolimus. Whether this provides additional prognostic value to IMDC criteria needs to be confirmed in a larger cohort. SMI does not seem to be predictive of everolimus-induced toxicity.