Body Composition in Patients with Radioactive Iodine-Refractory, Advanced Differentiated Thyroid Cancer Treated with Sorafenib or Placebo: A Retrospective Analysis of the Phase III DECISION Trial.

Background: Rates of adverse events with sorafenib were higher in the DECISION trial in radioactive iodine-refractory, advanced differentiated thyroid cancer (DTC) than in trials of sorafenib for other tumor types. One possible explanation is that sarcopenia, a known predictive factor of toxicity in patients with cancer, is more common in patients with DTC due to hormone suppressive therapy. Methods: This retrospective exploratory analysis was performed to assess whether the risk of early toxicity leading to dose modification (DMT) with sorafenib was higher in patients with sarcopenia compared with those without sarcopenia. The data set comprised patients from the phase III DECISION trial with a computed tomography scan available to determine muscle mass. The skeletal muscle (SM) cross-sectional area was used to determine the SM index and define sarcopenia. The end points were changes in body composition, DMT, early DMT (within 1 month), severe toxic events (STEs), and early STEs. Results: Overall, 365 patients were eligible for this analysis; baseline characteristics were well balanced between patients receiving sorafenib (n = 180) versus placebo (n = 185). Using a sarcopenia definition of an SM index less than the median sex-specific SM index, approximately half of the patients receiving sorafenib were at risk of sarcopenia (89/180; 49.4%), with wide geographical variation. At 6 months, the mean weight, body mass index, and lean body mass of patients receiving sorafenib were lower than at baseline and significantly lower than for patients receiving placebo (all p < 0.0001). Most DMTs and STEs occurred in the first month of treatment. There was a nonsignificant trend for more early DMTs in patients with sarcopenia compared with those without sarcopenia (55.3% vs. 44.7%, respectively; p = 0.2273). Conclusions: These results show a significant effect of sorafenib on muscle mass. However, there was no association between sarcopenia and DMT or early DMT, in contrast to observations in hepatocellular and renal cell carcinoma.