Do CT perfusion measures predict early clinical response in patients with advanced renal cell carcinoma

496Background: We need biomarkers of response to guide treatment decisions in RCC. Our pilot study uses perfusion CT to assess early changes in tumor vascularity in response to targeted therapies. We will determine if perfusion CT measurements can help predict response to therapy after 1 week of treatment in patients with metastatic RCC. Methods: Nine patients with metastatic renal cell carcinoma treated with targeted therapy have been enrolled to date. CT perfusion measures were collected: (1) prior to treatment, (2) 7-10 days after start of treatment, and (3) 12 weeks after start of treatment. At each time point, 5 measures were analyzed: (1) blood volume (BV), (2) blood flow (BF), (3) mean transit time (MTT), (4) flow extraction product (FEP), and (5) tumor size. Clinical response was determined based on RECIST criteria. Univariate and multivariate logistic regression analyses were conducted to determine the association of the CT perfusion measures and clinical response. The relationship between clinic...