Comparison of four early posttherapy imaging changes (EPTIC; RECIST 1.0, tumor shrinkage, computed tomography tumor density, Choi criteria) in assessing outcome to vascular endothelial growth factor-targeted therapy in patients with advanced renal cell carcinoma.

BACKGROUND: Vascular endothelial growth factor (VEGF)-targeted therapy has become standard treatment for patients with metastatic renal cell cancer (mRCC). Since these therapies can induce tumor necrosis and minimal tumor shrinkage, Response Evaluation Criteria in Solid Tumors (RECIST) may not be optimal for predicting clinical outcome.
OBJECTIVE: To systematically determine the optimal early posttherapy imaging changes (EPTIC) to separate responders and nonresponders at the first posttreatment follow-up computed tomography (CT). DESIGN, SETTING, AND PARTICIPANTS: Seventy mRCC patients with 155 target lesions treated with first-line sunitinib, sorafenib, or bevacizumab at academic medical centers underwent contrast-enhanced thoracic and abdominal CT at baseline and first follow-up after therapy initiation (median: 78 d after therapy initiation; range: 31-223 d). MEASUREMENTS: Evaluations were performed according to (1) RECIST 1.0; (2) Choi criteria; (3) tumor shrinkage (TS) of ≥10% decrease in sum of the longest unidimensional diameter (SLD); and (4) 15% or 20% decrease in mean CT tumor density. Correlation with time to treatment failure (TTF) and overall survival (OS) were compared and stratified by response to each of the radiologic criteria. RESULTS AND LIMITATIONS: Eleven patients were considered responders by RECIST 1.0; 49 based on Choi criteria; 31 patients had ≥10% decrease in the SLD; and 36 and 32 patients had ≥15% and ≥20% decrease, respectively, in mean tumor density on CT. Only the threshold of 10% decrease in the SLD was statistically significant in predicting TTF (10.4 vs 5.1 mo; p=0.02) and OS (32.5 vs 15.8 mo; p=0.002). Receiver operating characteristic analysis yielded a 10% decrease in SLD as the optimal size change threshold for responders. The retrospective nature of the study and measurements by a single oncoradiologist are inherent limitations.
CONCLUSIONS: In the retrospectively analyzed study population of mRCC patients receiving VEGF-targeted agents, a 10% reduction in the SLD on the first follow-up CT was an optimal early predictor of outcome.