AJR Am J Roentgenol 1998 Oct;171(4):1103-10
Imaging of oncologic patients: benefit of combined CT and FDG PET in the
diagnosis of malignancy.
Eubank WB, Mankoff DA, Schmiedl UP, Winter TC 3rd, Fisher ER, Olshen AB, Graham MM, Eary
JF.
OBJECTIVE: The purpose of this study was to assess the benefit of combined CT and
18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) in diagnosing malignancy.
MATERIALS AND METHODS: The records of 26 patients with intraabdominal and intrathoracic
neoplasms who underwent CT and FDG PET between January 1995 and September 1996 were
retrospectively reviewed. Most of these patients had inconclusive findings on prior CT for
the diagnosis of malignancy. Only sites of potential malignant disease were included in
the data analysis. Presence or absence of malignancy was confirmed by histopathology or
follow-up CT. Three observers experienced in abdominal imaging used CT findings alone to
estimate level of suspicion (1 = definitely not malignant to 5 = definitely malignant) for
primary or recurrent neoplasms (n = 21), distant metastases (n = 25), and neoplastic nodal
involvement (n = 18). Six weeks later the three observers reviewed the same CT
examinations supplemented with FDG PET and reestimated suspicion of malignancy. Receiver
operating characteristic methodology was used to analyze the results. Sensitivity,
specificity, positive and negative predictive values, and accuracy in diagnosis of
malignant disease were calculated using level 4 (probable malignancy) as the cutoff for
the presence of disease. RESULTS: The mean area under the receiver operating
characteristic curve, indicating successful diagnosis of malignancy, was .82 for CT alone
and .92 for CT with FDG PET (p < .05). The accuracies for diagnosis of primary or
recurrent neoplasms, distant metastases, and neoplastic nodal involvement were 62%, 68%,
and 83%, respectively, for CT alone and 81% (p = .06), 88% (p = .03), and 89% (p >
.25), respectively, for CT with FDG PET. Also, supplemental FDG PET imaging improved
observer confidence and accuracy in diagnosing recurrent neoplasm in four (36%) of 11
patients who had undergone surgery or chemoradiation and in diagnosing four (29%) of 14
extrahepatic sites that had potential metastases. CONCLUSION: Diagnosis of malignancy in
oncologic patients is significantly improved when CT is supplemented with FDG PET.
Combined imaging is particularly helpful in the evaluation of potential recurrence in
previously treated patients and for diagnosing extrahepatic lesions that may be distant
metastases.
