Physicians at the Weill Medical College of Cornell and the New York Presbyterian Hospital in New York reported on 23 patients who received PET scans before and after one cycle of treatment and also at the completion of chemotherapy. PET was accurate 87% of the time after one cycle but only 70% of the time after completion of chemotherapy. Sensitivity, i.e., the ability to detect the FDG and hence disease, was also significantly higher after one cycle, at 82% v. 45.5%. In particular, in cases in which results from the first cycle differed from the results following completion of therapy, the results from the first cycle scan were more accurate. Ninety percent of patients with positive 18F-FDG PET results after one cycle experienced disease relapse, while 85% who had negative 18F-FDG PET findings after one cycle remained in remission. The authors concluded that PET was a better predictor of outcome and response to therapy after just one cycle of chemotherapy than after completion.
PET stands for positron emission tomography. Because of its unique ability to measure metabolic activityor the efficiency of the cells converting food to energy--PET provides accurate, noninvasive detection and staging of many cancers. A radiopharmaceutical, such as 18F-FDG (fluorodeoxyglucose), which includes a radionuclide (a radioactive element) is injected into the patient and gives off signals that are measured by a PET scanner. Because cancer cells are more metabolically active, they show up on the PET images more intensely than normal tissue.