At radiation planning subjects will have a PET-CT. The CT scan - also called computerized tomography or just CT - combines a series of X-ray views taken from many different angles to produce cross-sectional images of the bones and soft tissues inside the body. A PET is a highly specialized imaging technique that uses short-lived radioactive substances (such as FDG a simple sugar labeled with a radioactive atom) to produce three-dimensional colored images of those substances functioning within the body. These images are called PET scans and the technique is termed PET scanning. PET scanning provides information about the body's chemistry not available through other procedures. Unlike CT or MRI (magnetic resonance imaging), techniques that look at anatomy or body form, PET studies metabolic activity or body function.

This benefit lies in the potential to adapt the treatment plan based on an intratreatment PET-CT. This may also be of significant prognostic utility, at an early enough time point to potentially alter treatment accordingly.

This study will evaluate the prognostic value of intra-treatment functional imaging on clinical relevant tumor endpoints (i.e. locoregional control, freedom from distant metastases, and overall survival).Comparison of intra-treatment FDG-PET indices will identify two groups of responses: PET responses and PET non-responses, which will correlate with prognosis.