Abstract
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Introduction: Thoracic malignancies are among the most common malignancies diagnosed both in the United States and worldwide. Radiation therapy (RT) plays an important role in the treatment of thoracic malignancies. Depending on the primary disease site and tumor stage, RT can be used as monotherapy, or as part of multimodality therapy for curative intent, or for palliative reduction of advanced disease. In fact, more than 50% of all patients with thoracic malignancies will receive RT as part of their multidisciplinary care. 18F-Fluorodeoxyglucose positron emission tomography (PET) is commonly used for initial cancer diagnosis, disease staging, outcome prognostication, radiation therapy (RT) planning, treatment response assessment, and detection of recurrent disease. In radiation oncology, PET plays a major role in RT target volume delineation, treatment response monitoring, evaluation for radiation-induced toxicities, and verification of radiation dose delivery. As advanced techniques such as intensity-modulated radiation therapy (IMRT) and proton therapy have increased in utilization, positron emission tomography/computed tomography (PET/CT) have played increasingly critical roles in the target delineation of tumors for radiation oncologists delivering conformal treatments, especially when treating thoracic malignancies. In RT, improvement in target localization permits reduction of tumor contour margins, consequently reducing the volume of normal tissues irradiated. Furthermore, smaller treated target volumes create the possibility of dose escalation, leading to increased chances of tumor cure and control. In this review, we will detail the current uses of PET/CT in thoracic radiation oncology with a focus on lung cancer, and describe future roles that PET is increasingly expected to play for lung cancer and other thoracic malignancies. Also, the following subjects will be reviewed: 1. PET for diagnosis and staging. 2. Thoracic RT techniques. 3. PET/CT for RT target delineation. 4. Pre-treatment PET for outcome prognostication and treatment response prediction. 5. Post-treatment PET for outcome prognostication and treatment response prediction. 6. Assessment of radiation-induced toxicity on PET imaging.