Body composition by computed tomography as a predictor of toxicity in patients with renal cell carcinoma treated with sunitinib

Background: Sunitinib is a standard first-line option for metastatic renal cell carcinoma (mRCC). Body composition is a prognostic factor in cancer patients and patients with loss of skeletal muscle mass and fat-free mass (FFM) are prone to dose-limiting toxicity (DLT) during targeted drug therapy. We investigated whether body composition by computed tomography predicted DLT from sunitinib in mRCC. Methods: Patients with clear cell mRCC receiving sunitinib (50 mg) were included. Skeletal muscle cross-sectional area at L3 was measured by computed tomography. Sarcopenia was defined using published cutoffs. Toxicity was assessed after 4 cycles of the drug. Results: Fifty-five patients (43 male), mean age 64 years were included. Overall, 33% (N = 18) of all patients were sarcopenic and of these 12.7% (N = 7) were sarcopenic and overweight or obese. DLT occurred in <6 months in 53% of patients (44% male vs. 83% female) and those who experienced DLT were older (68 vs. 60 y), had a lower skeletal muscle index (51.7 vs. 59.4 cm²/m²), a lower FFM (51.4 vs. 57.7 kg), and received a higher drug dose in mg/kg FFM (0.9 vs. 0.8). Patients with the lowest compared with the highest measurements of skeletal muscle mass experienced more DLT, respectively, 92% versus 57% and experienced on average 5 toxicities versus 2. Conclusions: Sarcopenia is prevalent in patients with mRCC, is an occult condition in patients with normal/high body mass index, and is a significant predictor of DLT in patients receiving sunitinib. Our results highlight the potential use of baseline body composition to predict toxicity.