Role of Positron Emission Tomography–Computed Tomography in Pulmonary Neoplasms
Computed tomography (CT) revolutionized the management of patients with cancer for diagnosis, staging, and assessing disease response to therapy. PET-CT is now a routine body oncology imaging modality, and is particularly well suited for patients with lung cancer. PET-CT can now be considered the standard of practice for staging non–small cell lung cancer, either suspected or histologically proven. As locoregional spread of lung cancer is to hilar and mediastinal lymph nodes, adding FDG-PET to CT increases diagnostic accuracy by detecting metastatic involvement of non-enlarged nodes. Distant metastatic patterns for non–small cell lung cancer chiefly include liver, adrenal glands, and bone, and here FDG-PET provides sensitivity for the small metastases easily overlooked on CT interpretation or occult on the CT images. Lung cancer also has a propensity for soft tissue metastases, especially in the setting of treated disease, and these are often depicted on FDG-PET and only identified on CT as easily overlooked or subtle findings. PET-CT combines the advantages of CT for largely anatomically defined criteria such as the T stage with the added sensitivity of FDG-PET metabolic assessment of small nodal or distant metastatic disease defining the N and M stage. Therapy response assessment can be broadly thought of as both assessing response of malignant disease to therapy during the course of therapy, usually referred to as therapy monitoring, and restaging of extent of malignant disease following completion of a therapy regimen. In either case, the imaging examination is performed for the purpose of guiding subsequent treatment, be it systemic or directed. A developing application of FDG-PET imaging is therapy monitoring early in the course of chemotherapy or assessing neoadjunctive therapy before completion.
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