Lung Functional Avoidance Radiotherapy Using Hyperpolarized Xenon MRI

Overview

Cancer radiation treatment plans that employ lung functional avoidance methods require 3D maps that differentiate regions of healthy lung function from regions of functional compromised tissue to deliver sufficient dose to the tumor while preserving as much functioning lung as possible. Hyperpolarized xenon-129 MRI can provide maps of ventilatory function and gas exchange to the bloodstream. Improving treatment plans based on this novel imaging modality could reduce risk or severity of radiation pneumonitis and improve post-treatment quality of life.

Customized 3D planning of radiation therapy for lung cancer delivers a lethal dose to the tumor region while avoiding important structures (spine) and organs (esophagus, heart, lungs). Since radiation dose to functioning lung is associated with acute radiation pneumonitis and chronic radiation fibrosis, researchers seek to shift dosage preferentially away from lung regions with highest function. Several lung functional imaging modalities have been investigated (ventilation-perfusion SPECT and PET, 4DCT, hyperpolarized 3He). These studies indicate that regional ventilation is not the optimal biometric. What is needed is a high-resolution imaging modality, tolerable to patients who have difficulty holding their breath, that delineates regions of full lung function warranting preservation, and also identifies regions whose function is irrevocably gone. The investigators propose a translational study applying Hyperpolarized Xenon (HXe) MRI to improve lung-health outcomes for lung cancer patients treated with radiation therapy. This study will focus on a patient cohort with significant heterogeneity: new patients with lung cancer and GOLD stage 3+ emphysema as a comorbidity and patients receiving RT for their second (primary) lung cancer. Optimizing radiation therapy treatment plans could provide a statistically significant benefit within a manageably small patient cohort. Maps will delineate three regions of functionality: regions of full function, having both ventilation and gas exchange to blood (where radiation should be avoided or minimized), regions where function is irrevocably absent (where radiation dose can be increased/maximized), and regions where function may be present or recoverable (where radiation should remain below or at the normal dose limit). Regions of lungs with absent function will have highest priority for receiving radiation during the RT procedure, while healthy regions will be avoided. It is expected that following this functional avoidance procedure will result in a decrease in the radiation induced lung injury reported events and a better outcome of the radiation treatment.

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