Endemic Infection Reduces Lung Cancer Diagnostic Specificity

Endemic lung infection may have a significant impact on the accuracy of malignancy diagnosis

medwireNews: Endemic lung infection significantly hampers the diagnosis of lung cancer using 18F-fluorodeoxyglucose –positron emission tomography (FDGPET), meta-analysis suggests.

The research published in JAMA indicates that FDG–PET has a specificity of just 61% in regions with endemic infections, such as tuberculosis, histoplasmosis and coccidioidomycosis, compared with 77% in areas without widespread lung disease.

“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”, caution Eric Grogan, from Vanderbilt University Medical Center in Nashville, Tennessee, USA, and co-authors.

The researchers examined data from 70 articles reporting results for 8511 nodules assessed by FDG–PET, 60% of which were malignant.

The overall unadjusted pooled analysis indicated FDG–PET to be 75% specific and 89% sensitive for the detection of lung cancer in patients with lung nodules or masses but found significant heterogeneity across the values reported.

Of note, 10 studies reported FDG–PET results for 1431 patients in populations with endemic infectious lung disease, finding granulomas accounted for between 45% and 75% of benign diagnoses, the team reports.

FDG–PET was 16% less specific for lung cancer diagnosis in patients residing in endemic versus nonendemic regions overall and 14% less specific when only including data from “rigorously conducted and well-controlled studies”, write Eric Grogan and co-authors.

However, FDG–PET sensitivity was not significantly affected by endemic infection status, with an adjusted sensitivity of 94% versus 88% in endemic versus nonendemic regions.

The researchers compared studies using FDG–PET and those using FDG–PET plus computed tomography (CT) and found the single technology had slightly worse specificity for diagnosing lung cancer, at around 70%, compared with combined imaging but they note that this could be due to publication bias.

“We have shown that the specificity of FDG-PET/CT for the diagnosis of lung cancer was overstated in regions with endemic infectious lung disease and could lead to unnecessary biopsies or thoracotomies for indeterminate lung nodules”, the researchers conclude.

“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.”

Reference

Deppen S, Blume J, Kensinger C, et al. Accuracy of FDG–PET to diagnose lung cancer in areas with infectious lung disease. A meta-analysis.  JAMA 2014; 312(12): 1227–1236. doi:10.1001/jama.2014.11488

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