Washington, February 7 : A multi-institutional study suggests that positron emission tomography (PET) is more reliable than computed tomography (CT) when it comes to the determination of malignancy of a lung nodule.
"CT and PET have been widely used to characterize solitary pulmonary nodules (SPNs) as benign or malignant. Almost all previous studies examining the accuracy of CT for characterizing lung nodules, however, were performed more than 15 years ago with outdated technology and methods, and previous PET studies were limited by small sample sizes," said James W. Fletcher, professor of radiology at Indiana University School of Medicine in Indianapolis.
"Detecting and characterizing SPNs is important because malignant nodules represent a potentially curable form of lung cancer. Identifying which SPNs are most likely to be malignant enables physicians to initiate the proper therapy before local or distant metastases develop," Fletcher added.
During the study, a panel of experts independently interpreted PET and CT images on 344 patients, and compared their determination of benign and malignant nodules to pathologic findings or changes in SPN size over the next two years.
The researchers found that the two modalities were equally good at determining whether
The researchers found that when PET and CT results were interpreted as "probably" or "definitely" benign, the results were "strongly associated with a benign final diagnosis". According to them, the modalities were equally good at making this determination.
They say that PET's higher accuracy in characterizing a nodule as benign or malignant, however, resulted in correctly classifying 58 percent of the benign nodules that had been incorrectly classified as malignant on CT.
When PET interpreted SPNs as definitely malignant, a malignant final diagnosis was 10 times more likely than a benign.
SPNs are commonly encountered in both primary and specialty settings, often showing up on chest X-rays obtained for some other purpose than cancer screening, and are often the first manifestation of lung cancer.
The question for such patients then becomes whether to undergo surgery, undergo a needle biopsy or "watch and wait" to find out if the nodule is benign or malignant but treatable.
"In patients with an untreated and undiagnosed SPN between 7 and 30 millimeters, PET provides better identification of malignant nodules that require a more aggressive treatment approach," said Fletcher.
"PET in combination with CT can also provide good identification of those nodules that are most likely to be benign, suggesting that a 'watch and wait' strategy can be adopted in lieu of unnecessary invasive-and expensive-procedures such as needle biopsy or surgery," he added.
The study has been published in the Journal of Nuclear Medicine.