Functional imaging in predicting response to antineoplastic agents and molecular targeted therapies in lung cancer: A review of existing evidence

The increasing use of FDG-PET (18F-2-fluoro-2-deoxy-d-glucose positron emission tomography) imaging in the staging of non-small-cell lung cancer (NSCLC) may result in a significant shift in stage distribution, with an increased percentage of patients staged as having metastatic disease and consequently a higher percentage of patients treated with systemic therapy. The amount of FDG-PET uptake in primary lung lesions has been shown to be correlated with tumour growth rate. Data suggest that tumours with increased glucose uptake are presumably more metabolically active and more biologically aggressive, and standardized uptake value (SUV) at PET may be regarded as a prognostic factor. Growing evidence suggests that PET may be used as a predictive marker to assess the activity of antineoplastic agents, allowing close monitoring of the efficacy of the treatment in order to be able to switch earlier to alternative therapies according to the individual chemosensitivity of the tumour.Currently the value of FDG-PET for monitoring response is complicated by the heterogeneity of the published data on the methods used for FDG quantification and the selection of the primary targets and clinical endpoints. As a result, objective validation of proposed thresholds of responsiveness is lacking.This article discusses the assessment of treatment response in NSCLC patients using functional imaging, and emphasizes advantages and limitations in clinical management.