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

Abstract

496 Background: 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 clinical response and individual measure at each time point, change in each measure at each time point, and the rate of change over the measure across all time points (slope) were evaluated in each patient. Results: We found that two blood volume measurements are associated with outcome. 5/9 (56%) patients had stable disease and 4/9 (44%) had progressive disease. Decrease in blood volume from time prior to treatment to 7-10 days after start of treatment was significantly associated with decreased odds of having stable disease (OR 0.63 (0.4-0.99), p=0.04). When examining the rate of change, the slope of blood volume was significantly associated with decreased odds of having stable disease (OR 0.52 (0.27-1.01), p=0.05). Univariable logistic regression for each individual CT measure, FEP prior to treatment (OR 1.07 (0.99-1.15), p=0.08) and 12 weeks after treatment (OR 1.13 (0.99-1.29), p=0.06) were not significantly associated with stable disease. Conclusions: Changes in blood volume including absolute difference as well as rate of change of blood volume were statistically significantly different between patients with stable disease versus progressive disease. Clinical trial information: NCT01926990.