30. Follow-up of Patients with Single Pulmonary Nodules and Negative 18F-Fluorodeoxyglucose Positron Emission Tomography Scans

Purpose: Positron Emission Tomography with ¹⁸F-Fluorodeoxyglucose (¹⁸FDG-PET) is becoming the noninvasive test of choice to evaluate patients with single pulmonary nodules (SPN). While positive scans yield a high sensitivity for malignancy, the significance of negative scans remains unclear. The purpose of this study was to evaluate the prognostic value of negative ¹⁸FDG-PET in patients with SPN.

Methods: From January 1998 to January 2000, 59 patients with non-calcified parenchymal SPN underwent ¹⁸FDG-PET evaluations. From a total of 14 pathologically proven tumors 12 patients had positive ¹⁸FDG-PET scans (sensitivity 86%, PPV 100%) with a mean SUV of 5.6. A total of 24 patients (41%) with negative ¹⁸FDG-PET scans were followed up with serial chest x-ray (CXR) and/or Computed tomography (CT) for a period of 6 to 24 months (mean 10.4 months). Histology specimens were available in 5 patients. Two patients had a second PET scan.

Results: Nineteen of the 24 negative ¹⁸FDG-PET patients (79.2%) had no evidence of intrathoracic neoplasia at subsequent follow up by CT and/or CXR, for an overall NPV of 86.3%. Two patients (8.3%) had transthoracic needle biopsies that were positive for malignancy after the PET scan. The remaining 3 patients developed intrathoracic malignancies during the follow up period (6, 6, and 9 months respectively) by CT and/or CXR. Repeat ¹⁸FDG-PET scans were positive in 2 patients.

Conclusion: ¹⁸FDG-PET appears to effectively characterize patients at low risk for malignant transformation of SPN discovered by CT. Blinded, randomized controlled trials are needed for further evaluation.