Incremental value of fusion imaging with integrated PET-CT in oncology

The purpose of this study was to assess the incremental value of integrated F-18 FDG PET-CT imaging compared with either alone for evaluation of patients with body malignancies.

Images from 173 consecutive patients with body malignancies referred for integrated PET-CT imaging were reviewed. A CT with contrast performed within 2 months of PET-CT was available for 74 patients.

There was agreement between the transmission CT (TrCT) and PET interpreted separately in 65% (112 of 173) of patients. Interpretation of integrated PET-CT had an incremental diagnostic value in 17.9% (31 of 173) of the total patient population. Data was analyzed further excluding patients for whom further analysis was not relevant: 1) 20% (34 of 173) of patients with normal TrCT and PET and 2) 11% (19 of 173) of patients with disseminated metastases (too numerous to count) on both TrCT and PET. Among the 120 other patients, PET interpreted alone was positive in 195 body regions and CT-positive in 178 body regions with agreement for all regions in 49% (59 of 120) of patients and discordance or equivocal lesions in 51% (61 of 120) of patients. Integrated PET-CT had an incremental diagnostic value in 27% (31 of 120) of patients. Contrasted CT scan demonstrated hepatic lesions in 5 and extrahepatic lesions in 3 patients overlooked on TrCT; all 8 of these lesions were PET-positive. There was incremental impact on the management of 12.5% (15 of 120) of patients.

After excluding patients with a normal PET-CT or disseminated disease, there was an incremental diagnostic value of integrated PET-CT imaging in 27% (31 of 120) and incremental impact on management in 12.5% (15 of 120) of patients. CT with contrast did not demonstrate lesions not appreciated by PET-CT.