CT response assessment combining reduction in both size and arterial phase density correlates with time to progression in metastatic renal cancer patients treated with targeted therapies

Background: Response assessment is critical in evaluating effectiveness of anticancer treatment. Tyrosine kinase inhibitors (TKIs) in renal cell carcinoma (RCC) are associated with significant clinical benefit but may not result in significant tumour size reduction. Thus standard size-based response assessment with RECIST is insensitive, resulting in low response rates which do not reflect disease control measured by time to progression. We compared the use of combined size and density response criteria with standard size based criteria in metastatic RCC patients treated with TKI's.Patients and methods: CT scans from 32 patients with metastatic RCC treated with either sunitinib (18) or cediranib (14) were assessed. 12 patients were excluded from the analysis as 10 had non-contrast enhanced scans due to renal impairment and 2 stopped treatment due to toxicity. 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% d...