Solitary pulmonary nodules that prove to be malignant are much more likely to be identified as such with PET than with CT, a multicenter team reports in the Journal of Nuclear Medicine.

by Martha Kerr

Solitary pulmonary nodules that prove to be malignant are much more likely to be identified as such with positron emission tomography (PET) than with computed tomography (CT), a multicenter team reports in the February issue of the Journal of Nuclear Medicine.

"Detecting and characterizing solitary pulmonary nodules is important because malignant nodules represent a potentially curable form of lung cancer. Identifying which (nodules) are most likely to be malignant enables physicians to initiate the proper therapy before local or distant metastases develop," lead investigator Dr. James W. Fletcher of the Indiana University School of Medicine, Indianapolis, explained in comments to Reuters Health.

Dr. Fletcher and colleagues enrolled 532 patients with solitary pulmonary nodules, ranging in size from 7 mm to 30 mm, which had been newly diagnosed on radiography but not yet treated.

All patients underwent diagnostic CT and 18F-FDG-enhanced PET. Biopsies of the nodules were used for confirmation of the diagnosis. A blinded panel of five experts rated PET and CT scans on a five-point scale.

A definitive diagnosis was established for 344 participants. The prevalence of malignancy was 53 per cent and the average size of a malignant nodule was 16 mm.

The investigators made a judgment of 'definitely benign' in 33 per cent of nodules analyzed with PET and in nine per cent of those analyzed with CT. Diagnoses of 'probably benign' were 27 and 12 per cent, according to PET and CT findings, respectively.

The likelihood ratios for PET and CT results for the combined ratings of 'definitely benign' or 'probably benign' were 0.10 and 0.11, respectively. The corresponding likelihood ratios for PET and CT results for the combined ratings of 'indeterminate,' 'probably malignant' or 'definitely malignant' were 5.18 and 1.61.

PET inter- and intraobserver reliability was superior to that of CT.

"Definitely and probably benign results on PET and CT strongly predict benign solitary pulmonary nodules," Dr. Fletcher and colleagues conclude. "However, such results were three times more common with PET."

"Definitely malignant results on PET were much more predictive of malignancy than were these results on CT. A malignant final diagnosis was approximately ten times more likely than a benign final diagnosis in participants with PET results rated definitely malignant," the researchers conclude.

"Some might argue that with the advent of integrated PET/CT scanners, our comparison of dedicated PET and CT technology is dated," the investigators acknowledge. "There is some evidence that integrated PET/CT is more accurate than dedicated PET for lung cancer staging."

"In this regard, and in uncommon circumstances, the CT component might help to improve the performance of PET by identifying rapid growth consistent with an infectious process, providing alternate diagnostic hypotheses, demonstrating a typical pattern of bronchioloalveolar carcinoma, and similar advantages."

"A paper analyzing the economic implications is in progress at this time," Dr. Fletcher added.


Source: Reuters

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