Early skeletal muscle loss during target therapy is a prognostic biomarker in metastatic renal cell carcinoma patients

Skeletal muscle depletion is common in patients with advanced cancer and may be associated with a poor outcome. To investigate whether the changes in skeletal muscle in metastatic renal cell carcinoma (mRCC) patients receiving targeted therapy are associated with clinical outcome, we undertook an observational cohort study using data from a number of randomized clinical trials previously conducted at the Fudan University Shanghai Cancer Center. The muscle mass was evaluated by comparing computed tomography images obtained at baseline with those obtained after 3–4 months of treatment. A total 101 patients were included in the study. The mean skeletal muscle area reduced from 41.6 cm(2)/m(2) to 39.9 cm(2)/m(2) after 3–4 months of targeted therapy. In multivariable analyses adjusted for the number of baseline covariates, muscle loss ≥5% was shown to be a significant prognostic factor for both progression-free (hazard ratio [HR]: 1.744, 95% confidence interval [CI]: 1.077–2.826, P = 0.024) and overall survival (HR: 2.367, 95%CI: 1.253–4.469, P = 0.008). The addition of muscle loss to the Heng model significantly improved its discriminative ability. In summary, early skeletal muscle loss is frequently observed in mRCC patients and can add prognostic information to current clinical risk scores.