Drugs that target vascular endothelial growth factor (VEGF), such as sunitinib, sorafenib and bevacizumab, are now standard therapy for patients with metastatic renal cell carcinoma (RCC). These agents can induce necrosis of tumor tissue, but generally cause only minimal tumor shrinkage. According to RECIST (response evaluation criteria in solid tumors)—a set of widely used, imaging-based criteria with which to identify responders and nonresponders to anti-cancer therapy—a 30% decrease in the sum of longest diameter (SLD) of target lesions indicates a partial response. This threshold is, however, seldom reached in patients with metastatic RCC receiving targeted therapy.

In a retrospective study, Krajewski and colleagues compared the power of four imaging parameters (RECIST 1.0, Choi criteria, tumor shrinkage and tumor density) to predict—at an early stage of treatment—which patients are likely to respond to ongoing VEGF-targeted therapy.

...≥10% decrease in SLD ... was the best [early] predictor of a good outcome...

70 consecutive patients harboring a total of 155 target lesions underwent CT at baseline and at the first post-treatment follow-up visit, a median of 78 days after initiation of sunitinib (n = 31), sorafenib (n = 24) or bevacizumab (n = 15) therapy. RECIST 1.0 defined patients as having a partial response (≥30% decrease in SLD), progressive disease (≥20% increase in SLD) or stable disease (neither SLD criteria satisfied). A good Choi response was defined as ≥10% decrease in SLD or ≥15% decrease in mean CT tumor density (failure to meet either of these criteria was deemed a poor response). 10% decrease in SLD, and 15% and 20% decreases in mean CT tumor density, were also analyzed as independent predictors of outcome (time to treatment failure, and overall survival).

≥10% decrease in SLD was the only criterion that could differentiate responders from nonresponders on the basis of time to treatment failure (10.4 months in responders versus 5.1 months in nonresponders, P = 0.021) and overall survival (32.5 months versus 15.8 months, P = 0.002).

The authors conclude that a ≥10% decrease in SLD on first follow-up CT was the best predictor of a good outcome after VEGF-targeted therapy for metastatic RCC. Validation in an independent, prospective cohort will be required to confirm this finding.