Objectives: Sunitinib is a standard first line option for metastatic renal cell carcinoma
(mRCC). Body composition is a prognostic factor in cancer patients (pts) and pts with
loss of skeletal muscle mass (SMM) and fat free mass (FFM) are prone to dose limiting toxicity (DLT) during targeted drug therapy. We investigated if body composition by computed tomography (CT) predicted DLT from sunitinib in mRCC.
Methods: Pts with clear cell, mRCC receiving sunitinib 50mg were included. Skeletal muscle cross-sectional area at L3 was measured by CT. Sarcopenia was defined using published cut offs. Toxicity was assessed after 4 cycles of the drug.
Results: 55 pts (43 male), mean age 64yrs were included. 33% (N= 18) of all pts were
sarcopenic and of these 12.7 % (N=7) were sarcopenic and overweight or obese. DLT occurred in <6 months in 53% (44% M vs 83% F) and pts who experienced DLT were older (68 yrs vs 60 yrs), had a lower skeletal muscle index (51.7 vs. 59.4 cm2/m2), a lower FFM (51.4kg vs 57.7kg), and received a higher drug dose in mg/kg FFM (0.9 vs 0.8). Pts with the lowest compared with the highest measurements of SMM experienced more DLT, respectively 92% vs. 57% and experienced on average 5 toxicities vs. 2.
Conclusions: Sarcopenia is prevalent in patients with mRCC, is an occult condition in pts with normal/high BMI, and is a significant predictor of DLT in pts receiving sunitinib. Our results highlight the potential use of baseline body composition to predict toxicity.