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).
Age ≥ 18
Any patient undergoing radiation therapy for a cancer lesion in the abdomen in close proximity to OARs that is hypothesized to have differential displacement on inhale and exhale breath hold CT scans of the OAR relative to the tumor.
Patients need at least 3 fractions of RT
Critical OARs are within 2 cm of luminal GI structures, chest wall, or previous radiation fields
Inability to perform inhale or exhale breath holds during standard workflow CT simulation evaluation
Single group
Simulation and treatment imaging
Diagnostic testObtain inhale and exhale breath hold images planned to split radiation delivery between inhale and exhale breath hold phases. For radiotherapy courses with an odd number of fractions, the phase of breath hold with higher reproducibility or anatomic advantage will be used for the additional fraction of radiotherapy. If during the treatment planning the investigators determine that the patients will benefit from the multiple breath holds technique, the patients will be treated using the composite breath hold plan. Additional one or two cone beam CTs will be obtained on treatment days for all patients using the inhale and exhale breath hold technique.
Total dose to radiation targets and OARs
Total dose to radiation targets and OARs on standard workflow (FB ITV or exhale/inhale single breath hold phase only) compared to INEX RT. Unit: Gy
Positional change between a deep inhale and deep exhale breath hold
Evaluate the motion of critical OARs during inhale and exhale breath holding techniques during simulation and during daily treatments, including the magnitude of positional change between a deep inhale and deep exhale breath hold. Unit: mm
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