Although positron-emission tomography (PET) combined with 18F–fluorodeoxyglucose (FDG) is recommended for the noninvasive diagnosis of pulmonary nodules suspicious for lung cancer, in populations with endemic infectious lung disease, FDG-PET may not accurately identify malignant lesions.
An analysis of 70 studies reporting a total of 8,511 nodules, 5,105 (60%) of which were malignant, found that the “accuracy of FDG-PET for diagnosing lung nodules was extremely heterogeneous,” according to Stephen A. Deppen, PhD, of the Tennessee Valley Healthcare System and Vanderbilt University Medical Center, Nashville, and colleagues.
“Use of FDG-PET combined with computed tomography [CT] was less specific in diagnosing malignancy in populations with endemic infectious lung disease compared with nonendemic regions. These data do not support the use of FDG-PET to diagnose lung cancer in endemic regions unless an institution achieves test performance accuracy similar to that found in nonendemic regions,” the researchers wrote in the Journal of the American Medical Association.
The studies, published from October 1, 2000, through April 28, 2014, were culled from MEDLINE, EMBASE, and the Web of Science databases. Included articles reported information from more than 10 participants with benign and malignant lesions and sufficient to calculate sensitivity and specificity of FDG-PET to diagnose lung cancer. “Although the accuracy of FDG-PET/CT is superior to the accuracy of FDG-PET only, we included both modalities because they are still in use in the United States and elsewhere,” the authors explained. They did not find a significant difference in specificity between the modalities.
In populations with endemic infectious lung disease, FDG-PET/CT specificity was estimated to be 16% lower than in nonendemic regions. “This lower specificity persisted at 14% even for rigorously conducted and well-controlled studies,” the investigators reported. The average adjusted estimate of specificity in regions with endemic disease was 61% (95% confidence interval [CI] = 49%-72%) vs 77% (95% CI = 73%-80%) in nonendemic regions. “For rigorously conducted and well-controlled studies, the estimates of specificity in endemic and nonendemic regions were 66% [95% CI = 51%-78%] and 80% [95% CI = 74%-85%], respectively,” the authors reported.
“Histoplasmosis, coccidioidomycosis, and blastomycosis are the most prevalent fungal lung diseases in the United States, and are common etiologies of lung granulomas. Histoplasmosis and blastomycosis are endemic across much of the Mississippi, Ohio, and Missouri river valley regions through southern Ontario, Canada, whereas coccidioidomycosis is prevalent in the southwestern United States,” the researchers noted. Tuberculosis has been reported as the common etiology for granulomatous disease in China, Japan, and South Africa.
Overestimates of the specificity in FDG-PET/CT in regions with endemic infectious lung disease “could lead to could lead to unnecessary biopsies or thoracotomies for indeterminate lung nodules,” the investigators stated. “Knowledge of this limitation in such regions is especially important if low-dose CT screening for lung cancer is widely adopted and should be reflected in current nodule management guidelines.” ■
Deppen SA, et al: JAMA 312:1227-1236, 2014.