Inhale and Exhale Breath Holds to Improve the Radiation Therapy Accuracy in People With Upper Abdominal Cancers

This is a prospective quality improvement study. The INEX RT P study will prospectively evaluate INEX RT R that optimizes radiation dose delivery to the target while minimizing dose to critical organs at risk (OAR) by treating patients with different phases of breath hold (inhale and exhale) during the same course of SBRT. 15 patients with abdominal cancer whom are expected to achieve a dosimetric advantage from this technique due to OAR proximity to target will be treated using INEX RT. Investigators hypothesize increasing the dose to the RT target by at least 10% while simultaneously decreasing or maintaining dose to adjacent critical OARs when using a combination of breath hold positions to purposefully vary the position of OARs during different fractions of the same treatment course, when compared to RT treatments planned on a single breath hold phase alone (present standard of care).