Renal cell carcinoma, which forms in the lining of small tubes in the kidney, is the most common and aggressive type of renal tumor. Last year, there were 38,890 reported new cases in the US, and 12,840 of these resulted in death. MRI, CT or ultrasound are usually used to diagnose renal masses, but they do not show how aggressive the tumor is.Dr. Chaitanya R. Divgi from the University of Pennsylvania in Philadelphia and his colleagues at Memorial Sloan-Kettering Cancer Center in New York investigated imaging with PET/CT using the radiolabeled antibody cG250 to see if it could accurately identify renal cell carcinoma. The antibody cG250 has been shown to effectively target and bind to clear-cell renal carcinoma. And because PET/CT can measure tissue concentrations of radioactivity in three dimensions with high resolution and sensitivity, it seemed like a good method for imaging the antibody-tumor binding.As reported in the April issue of The Lancet Oncology, 26 patients with renal masses who were scheduled for surgery received an injection of the antibody one week before surgery. One patient received an inactive dose of the antibody and was excluded from further analysis. Images of the abdomen were taken three hours prior to surgery with a PET/CT scanner from GE Healthcare of Waukesha, Wis. The images were recorded as either positive or negative for antibody uptake.Of the 25 patients who received PET/CT, pathological diagnoses revealed that 16 had clear-cell renal carcinoma. PET/CT correctly identified the tumor in 15 of these, resulting in a sensitivity of 94 percent. The nine patients who did not have clear-cell carcinoma also were correctly identified by PET, resulting in a specificity of 100 percent.The researchers believe the results indicate that the cG250-PET/CT method can accurately identify aggressive renal cell carcinoma and can be used to help with treatment decisions.