Background: The growth rate, or doubling time, of radiographically indeterminate pulmonary abnormalities is an important determinant of malignancy. Prospective calculation of doubling time, however, delays diagnosis and treatment. Positron emission tomography (PET) using the glucose analogue fluoride-18 fluorodeoxyglucose (FDG) measures the enhanced glucose uptake characteristic of neoplastic cells. We postulated that if FDG activity correlates with doubling time, then PET may allow prompt diagnosis of lung cancer.
Methods: From March 1992 to July 1993, all patients with indeterminate focal pulmonary abnormalities were eligible for FDG PET imaging. In 53 patients, serial chest radiographs or computed tomograms were available and doubling time was computed. The FDG activity within the lesion was expressed as a standardized uptake ratio.
Results: The mean standardized uptake ratio (+/- SD) was 5.9 +/- 2.7 in 34 patients with cancer, versus 2.0 +/- 1.7 in 19 with benign disease (p < 0.001). Using a criterion of standardized uptake ratio 2.5 or greater for malignancy, the accuracy of PET was 92% (49 of 53). The standardized uptake ratio was significantly correlated with doubling time (r = -0.89; p = 0.002).
Conclusion: These data suggest a direct relation between tumor growth and FDG uptake in lung cancer. The technique of FDG PET demonstrates exceptional accuracy and may permit prompt diagnosis of lung cancer.