Low body mass index and sarcopenia associated with dose-limiting toxicity of sorafenib in patients with renal cell carcinoma

Background: Patients with severe depletion of skeletal muscle (sarcopenia) are prone to dose-limiting toxicity (DLT) during fluoropyrimidine therapy. We hypothesized that sarcopenia may also predict toxicity of targeted therapy drugs. Materials and methods: Metastatic renal cell cancer (RCC) patients (n = 55) received sorafenib 400 mg b.i.d. Weight, height and skeletal muscle cross-sectional area at the third lumbar vertebra were measured by computed tomography (CT). Toxicity was assessed. Results: DLT occurred in 22% of patients overall, of which three-quarters were dose reductions to 400 mg and the remainder entailed termination of treatment. DLT was most common (41%) in sarcopenic patients whose body mass index (BMI) was <25 kg/m ² and least common (13%) in patients who were not sarcopenic and/or overweight or obese (P = 0.03). Toxicity was especially prevalent in sarcopenic male patients with BMI < 25, with 71% of men with these characteristics being unable to continue treatment at 800 mg/day. By contrast, only 5% of male patients whose muscle index was above the cut-off for sarcopenia and only 11% of male patients whose BMI was >25 experienced a DLT. Conclusion: BMI < 25 kg/m ² with diminished muscle mass is a significant predictor of toxicity in metastatic RCC patients treated with sorafenib.