Hypoxia Imaging -Guided Radiotherapy of Nasopharyngeal Carcinoma

Nasopharyngeal carcinoma (NPC) differs from other head and neck malignancies in terms of its epidemiology, pathology, and treatment outcome . It is endemic in China and is one of the major public health problems. Concurrent radiotherapy and chemotherapy is the primary treatment for patients with NPC. Despite such aggressive treatment, many patients with locally advanced NPC still develop locally recurrent disease. Since local control is directly related to patient morbidity and mortality in NPC, there is a strong need to identify methods to further improve treatment outcome for NPC. One strategy to improve local control is to escalate the dose of radiotherapy. This is because local control has been shown to be directly related to the radiotherapy dose. Several different techniques, including brachytherapy, stereotactic radiosurgery, and dose-painting intensity modulated radiotherapy (IMRT), have been used to increase radiotherapy dose. However, due to the large number of critical anatomic structures near the nasopharynx, dose-escalation in NPC can also lead to increased toxicities. One technique that has achieved dose-escalation with minimal increase in toxicity is simultaneous modulated accelerated radiation therapy (SMART). The main challenge for such treatment is to identify the appropriate tumor volume to receive the high-dose radiotherapy. Conventional dose-escalation is conducted using computed tomography (CT) to identify the gross tumor volume (GTV). However, recent progress with F-18 fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG-PET/CT) in treatment planning allows more accurate tumor volume delineation. We hypothesize that the use of PET/CT in treatment planning can improve dose-escalation radiotherapy for NPC which in turn can improve therapeutic efficacy while reducing toxicity. PET/CT imaging of tissue hypoxia using \[F-18\]fluoromisonidazole (FMISO), the most widely used nitroimidazole imaging agent.Given that there has b