From the Department of Nuclear Medicine, University of Freiburg, Freiburg, Germany
Authors’ disclosures of potential conflicts of interest are found at the end of this article.
Address reprint requests to Wolfgang A. Weber, MD, Department of Nuclear Medicine, University of Freiburg, Hugstetterstrasse 55, 79106 Freiburg, Germany; e-mail: wolfgang.weber{at}uniklinik-freiburg.de
Overview: For patients with non-small cell lung cancer (NSCLC), measurements of tumor size on computerized tomography (CT) currently represent the standard for assessing tumor response to therapy. CT has become an extremely fast and robust technique that provides high-resolution images of the primary tumor, lymph node, and distant metastases. Although clinical experience and meta-analyses of large clinical trials demonstrate the usefulness of CT for response assessment, certain limitations of CT are also well recognized. CT frequently cannot differentiate between tumor and surrounding atelectasis, which can make size measurements inaccurate. Furthermore, it is generally not possible to differentiate viable tumor tissue from treatment-induced fibrosis. Finally, some treatments appear to improve patient survival without causing a rapid decrease in tumor size on CT. Positron emission tomography (PET) with the glucose analog fluorodeoxyglucose (FDG-PET) has been evaluated in several studies for monitoring tumor response to therapy. These studies indicate that metabolic changes during therapy are highly significantly correlated with survival. When response assessment by FDG-PET was compared with response assessment by CT, PET provided a higher accuracy for monitoring tumor response to chemoradiotherapy. Furthermore, PET may allow earlier identification of nonresponding tumors, which offers the opportunity for treatment adjustments. Multicenter trials further evaluating these encouraging findings obtained in several single-center studies are currently ongoing. In the future, it is expected that tumor response assessment will be based on a combination of PET and CT, as these modalities are likely to provide complementary prognostic information.
