Endemic lung infection compromises lung cancer diagnosis

By Eleanor McDermid, Senior medwireNews Reporter

The accuracy of lung cancer diagnosis using 18F-fluorodeoxyglucose–positron emission tomography (FDG–PET) may be compromised in areas with endemic infectious lung diseases, research suggests.

Previous studies in areas with endemic lung infections have shown “mixed results” for FDG–PET accuracy, so Eric Grogan (Vanderbilt University Medical Center, Nashville, Tennessee, USA) and co-workers undertook a meta-analysis to explore the matter further.

They examined data from 70 articles reporting results for 8511 nodules assessed by FDG–PET, 60% of which were malignant. Ten of these studies, involving 1431 patients, were based in areas with endemic lung disease.

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

Further analysis showed that FDG–PET had 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.

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”, Grogan et al report in JAMA.

However, the sensitivity of FDG–PET was not significantly affected by the presence of endemic infection, with adjusted sensitivities of 94% and 88% in endemic and nonendemic regions, respectively.

When comparing studies using FDG–PET with those using FDG–PET plus computed tomography (CT), the researchers found that FDG–PET alone had slightly worse specificity than combined imaging for diagnosing lung cancer, at around 70%, but they say that this could be due to publication bias.

In populations with endemic infectious lung disease, granulomas accounted for between 45% and 75% of diagnoses that proved to be benign. Tuberculosis was a frequent cause of granulomatous disease in studies from China, South Africa and Japan.

“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.”

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