CT response assessment combining reduction in size and arterial enhancement correlates with time to progression in metastatic renal cancer patients treated with TKIs

Abstract

e16062 Background: Targeted therapy is now the standard of care in advanced Renal Carcinoma (RCC). Response assessment by RECIST criteria is insensitive as treated tumours often have only a modest change in size despite the induction of significant necrosis and does not correlate with time to progression (TTP). The Choi criteria (10% size reduction or 15% contrast enhancement reduction) are routinely used in the assessment of GIST tumours treated with targeted agents. We report the use of combined size and density assessment in RCC metastases treated with either sunitinib or cediranib. Methods: CT scans from 32 patients with metastatic RCC treated with either sunitinib (18) or cediranib (14) were assessed. Scans from 10 patients were not evaluable as non-contrast enhanced scans were performed due to impaired renal function. Scans from a further 2 patients were excluded as they ceased treatment due to toxicity rather than progression. Scans from 20 evaluable patients at baseline and 12 weeks on treatment were assessed using RECIST, Choi, and modified criteria in which both a 10% decrease in size and 15% decrease in enhancement in the arterial phase were required to define a response (PR). A total of 60 lesions were assessed. Response assessment was performed using each of the three methods and correlated with time to disease progression (itself RECIST defined). Statistical analysis was performed using the Mann-Whitney U test. Results: There was no difference in TTP between RECIST defined PR (346.8 days) and SD (328.5 days) (P=0.965). TTP in Choi defined PR (358.4 days) and SD (189.6 days) groups showed improved but non-significant separation of TTP duration (P=0.266). TTP in PR (421.5 days) and SD (200.3 days) groups defined by a combined assessment of reduction in size and enhancement showed greatly improved separation (P=0.064). Conclusions: A combined reduction in both size and arterial phase enhancement of RCC metastases treated with TKIs correlates with time to progression. RECIST and standard Choi criteria appear inferior. No significant financial relationships to disclose.