Positron Emission Tomography (PET) in the Evaluation of Response to Therapy in Non-Small Cell Lung Cancer

In modern clinical oncology there is a growing need to diagnose the presence of disease as soon as possible, even when symptoms are not yet present or are minimal, to identify the response to treatment in patients that have been treated and to detect improvement or worsening of the disease as early as possible. Conventional imaging methods that rely on morphologic or structural data are very precise in the delineation of lesions, but frequently present a limited diagnostic efficacy in the evaluation of response to oncologic treatments. These imaging methods define response to treatment as a reduction of tumor volume, without considering molecular or functional aspects that appear earlier than the structural or anatomic changes. Positron emission tomography (PET) and PET-CT with 18F-fluorodeoxiglucose (FDG) are very useful in monitoring response to treatment, following chemotherapy and radiotherapy. Many studies have demonstrated that FDG PET is an accurate method to correctly detect response to therapy. Moreover, early therapy response evaluation with FDG PET can predict response to treatment and patient outcome. This allows tailoring treatments to the individual patient depending on the chemosensitivity and radiosensitivity of the tumor. Therefore, FDG PET is a diagnostic imaging method that has the potential to improve the probability of cure or improvement and reduce the adverse effects and cost of unnecessary or ineffective treatments. In the research and development of new therapies, the non-invasive imaging methods used are of great importance, especially PET as it supplies functional and molecular information. PET can be used to assess all the processes related with the development of a new drug, especially assessing evolution and outcome. Here we present a review of the available evidence regarding therapy response evaluation with PET and PET-CT in non-small cell lung cancer.