Evaluating Sunitinib Therapy in Renal Cell Carcinoma Using F-18 FDG PET/CT and DCE MRI

The maximum standardized uptake value (SUVmax) is a measurement of tumor metabolism as determined by the PET scan before and after 12-weeks of sunitinib therapy. Decreased SUVmax correlates to a reduction of tumor metabolism. Increased SUVmax correlates to an increase in tumor metabolism. Reduction or increased SUVmax will be determined as the change from baseline in uptake of F18 FDG. Results were based on the European Organization for Research and Treatment of Cancer (EORTC) for predicting progression free survival. EORTC criteria is a ± 25% change of SUVmax for assessment of progressive disease, stable disease and partial response.

Histopathologic findings were correlated to the pre-treatment 18F-fluorodeoxyglucose positron emission tomography (F-18 FDG PET/CT) scan. Outcome is reported as the number of participants for whom both histopathology and F-18 FDG PET/CT indicated that active cancers was present.

A comprehensive metabolic panel is a blood test that measures sugar (glucose) level, electrolyte and fluid balance, kidney function, and liver function. It was performed prior to the administration of gadolinium contrast. For patients with normal renal function, approximately 90% of gadolinium contrast is excreted through the urinary system. These patients have known renal cell carcinoma, so it was important to perform a metabolic function panel prior to gadolinium injection, specifically to determine kidney function. Reported as the number of patients for whom the initial comprehensive metabolic panel was within institutional standards.

Adverse events were monitored for on F-18 FDG PET/CT and DCE MRI imaging days: baseline (n=17); interim (n=12); and post-sunitinib therapy (n=17). Reported as the overall number of adverse events experienced.

The degree of tumor necrosis was measured using values obtained from dynamic contrast enhanced magnetic resonance imaging (DCE MRI) pre- and post-sunitinib therapy. Gadolinium contrast material given intravenously during the DCE MRI scan is used to improve visualization of blood vessels, tumors, and/or organs.

Tumor size was measured based on computed tomography (CT) pre- and post-sunitinib therapy. CT was performed immediately prior to the PET scan and is used to determine both the PET scan imaging area and PET image attenuation correction (AC). F-18 FDG PET provides the metabolic and physiologic data while CT provides the anatomical data.

Tumor size was measured using values obtained from DCE MRI pre- and post-sunitinib therapy. Gadolinium contrast material given intravenously during the DCE MRI scan is used to improve visualization of blood vessels, tumors, and/or organs.

Area under the curve (AUC) was measured using receiver operating characteristic (ROC) curve analysis. ROC curve analysis measures sensitivity (true-positives, correctly diagnosed positive pathologies) against specificity (true-negatives, correctly diagnosed negative pathologies or free of disease) of the DCE MRI scan. An area of 1.0 under the curve would equal a perfect test (with 100% sensitivity; 100% specificity) while an area of 0.5 would equal a useless test (50% sensitivity; 50% specificity).

Initial tumor size was measured using values obtained from computed tomography (CT) pre-sunitinib therapy. CT is performed immediately prior to the PET scan and is used to determine both the PET scan imaging area and PET image attenuation correction (AC). F-18 FDG PET provides the metabolic and physiologic data while CT provides the anatomical data.