['Little is known on factors predicting sunitinib toxicity. Recently, the condition of low muscle mass, named sarcopenia, was identified as a significant predictor of toxicity in metastatic renal cell cancer (mRCC) patients treated with sorafenib. We investigated whether sarcopenia could predict early dose-limiting toxicities (DLTs) occurrence in mRCC patients treated with sunitinib.', 'Consecutive mRCC patients treated with sunitinib were retrospectively reviewed. A DLT was defined as any toxicity leading to dose reduction or treatment discontinuation. Body composition was evaluated using CT scan obtained within 1 month before treatment initiation.', 'Among 61 patients eligible for analysis, 52.5% were sarcopenic and 32.8% had both sarcopenia and a body mass index (BMI)<25\u2009kg\u2009m(-2). Eighteen patients (29.5%) experienced a DLT during the first cycle. Sarcopenic patients with a BMI<25\u2009kg\u2009m(-2) experienced more DLTs (P=0.01; odds ratio=4.1; 95% CI: (1.3-13.3)), more cumulative grade 2 or 3 toxicities (P=0.008), more grade 3 toxicities (P=0.04) and more acute vascular toxicities (P=0.009).'] Do sarcopenia and body mass index predict sunitinib-induced early dose-limiting toxicities in renal cancer patients?