Brain metastases of lung cancer: Diagnostic accuracy of positron emission tomography with fluoro-deoxyglucose (FDG-PET)

The value of FDG-PET in oncology is currently investigated in clinical stud ies. There is only limited information on the usefulness of FDG-PET in the evaluation of distant metastases of lung cancer. The purpose of the present prospective investigation was to determine the diagnostic accuracy of FDG- PET in the detection of brain metastases of lung cancer. After intravenous injection of 220 +/- 50 MBq F-18-deoxyglucose PET acquisi tion was carried out using an ECAT ART scanner (CTI Siemens). Images were r econstructed using a filtered backprojection with a Hanning filter. PET dat a were analyzed by visual interpretation of coronal, sagittal and transvers al slices. PET scans were interpreted by two experienced nuclear medicine p hysicians without prior knowledge of the results of other imaging studies o r clinical data. Between March 1997 and July 1998 whole-body PET was performed in 417 patien ts with suspected lung cancer. 402 patients were used for statistical analy sis. Based on conventional brain imaging with CT (occasionally MRI), brain metastases were suspected in 17 patients (prevalence 4.2%). For FDG-PET alo ne, sensitivity was 82% (14/17) and specificity 38% (14/37). Therefore, dia gnostic accuracy of FDG-PET in detection of brain metastases was 93.5%. The low specificity of FDG-PET can be explained by reduced tracer uptake mainl y due to brain infarction or vascular encephalopathy in this group of elder ly patients. Our results indicate that due to its low specificity FDG-PET is not useful for the evaluation of brain metastases in the primary staging of patients w ith lung cancer.