Body Composition Variation and Impact of Low Skeletal Muscle Mass in Patients With Advanced Medullary Thyroid Carcinoma Treated With Vandetanib: Results From a Placebo-Controlled Study

Objectives: Vandetanib was approved by the U.S. Food and Drug Association for the treatment of advanced medullary thyroid cancer (MTC). Because body weight (BW) loss is observed in MTC and because low skeletal muscle mass (SM) is associated with drug toxicity, this study assessed effects of vandetanib on SM and adipose tissue (AT) and explored the association between SM, toxicity, and serum concentration of vandetanib. Methods: Thirty-three patients with MTC received vandetanib (n = 23) or placebo (n = 10) in the ZETA study. Visceral AT (VAT), sc AT (SAT), and SM were assessed with computed tomography imaging by measuring tissue cross-sectional areas (square centimers per square meter). Dose-limiting toxicities (DLTs) were prospectively recorded. Results: Early at 3 months, compared with placebo group who lost BW, muscle, and SAT, patients treated with vandetanib gained 1.5 kg BW (P = 0.02), 1.3 cm2/m2 (∼0.7 kg) of SM (P = 0.009), and 4.5 cm2/m2 (∼0.5 kg) of SAT (P = 0.004) and gained more VAT, 5.1 cm2/m2...