PET Scan for Lung Cancer

OncoLink Team
The Abramson Cancer Center of the University of Pennsylvania
Last Modified: May 7, 2013

Question

I am a medical student. I heard a lot of discussion of using PET scans as a diagnostic tool for staging non small-cell lung cancer. Can you provide me more information? Thanks!

Answer

Li Liu, MD, OncoLink editorial assistant, responds:

Lung cancer is the leading cause of death from cancer for both men and women in the United States. Accurate staging is essential, as it provides prognostic information and influences treatment options. Radiologic staging is pursued by using a combination of studies, which usually include contrast material-enhanced chest computed tomography (CT) through the liver and adrenal glands, PET/CT scan, and brain magnetic resonance (MR) imaging for all but very early-stage patients. No single modality provides all of the required information.

Positron emission tomography (PET) by using 2-[fluorine 18] fluoro-2-deoxy-D-glucose (FDG) has been shown to be an accurate imaging modality that complements conventional studies in evaluating patients with bronchogenic carcinomas. The rationale for tumor imaging with FDG is based on a fundamental property of tumors, namely, increased glucose metabolism. This process begins when tumor cells take up and shuttle FDG into glycolysis. Increased amounts of FDG begin to accumulate within the malignant cells, and this abnormal concentration produces a detectable signal, which is then captured simultaneously by the detectors, and the information is used to reconstruct the PET images (Nucl Med Biol 1996 Aug; 23(6): 717-35).

Many pulmonary abnormalities, particularly small nodules, remain indeterminate after conventional radiologic evaluation with CT imaging. Once an abnormality has been detected, PET scans can be very useful in differentiating benign from malignant small lesions. The overall sensitivity, specificity, and accuracy of PET in identifying malignant lesions are 96%, 88%, and 94%, respectively (Clin Chest Med 1993 Mar;14(1):111-9; J Nucl Med 1996 Jun;37(6):943-8). PET/CT scans can also better determine if lung cancer has spread, or metastasized, to the lymph nodes in the chest with greater sensitivity and specificity than conventional CT imaging. As a result of its excellent sensitivity, PET/CT has replaced radionuclide bone scintigraphy and CT imaging of the abdomen as a standard part of the staging work-up for non-small cell lung cancer.