Determine if radiation induced xerostomia (RIX) increases the frequency or duration of acid-reflux when re-measured approximately 6-12 weeks after RT (measured by # episodes, their duration, and Reflux Area Index (RAI). Reflux Area (RA) is the sum of the area under the curve for all episodes of pH<4 recorded during the study in units of Ph*minutes. The Reflux area index (RAI) is the RA corrected for the duration of the study (RA x 100/study duration).