Grant: Travel Awards - Institute Community Support

Cancer of the liver can often not be removed with surgery, and so other methods of treatment like radiation therapy must be considered. In stereotactic radiotherapy, very large doses are delivered to a tumor making it very important to ensure the location of a lesion in the liver is known accurately. A patient's breathing moves organs in the surrounding chest area, the liver being one. This creates a difficulty in precisely knowing the exact location of a liver cancer at any instant of a patient's breath. Gating in radiotherapy refers to the act of delivering radiation to a cancer only in one part of a patient's breath such as at the point of maximum inhale or exhale. In this way a precise dose is hypothetically delivered to the tumor, while the surrounding healthy tissue is spared. It is not yet well established whether gating allows for delivery of an accurate prescribed dose to a tumor, and if it alters the survival of cells following radiotherapy. Because gating provides dose to a tumor only in certain part of a patient's respiratory cycle, the overall treatment time increases up to 7 times in duration. 'Filter free' accelerators are able to deliver a dose ~4 times faster than their predecessors, making their use favorable. This research explores how dose accumulation differs when radiation delivery is gated as opposed to being delivered in one instance. Further, the change in cell survival following the two methods of radiotherapy is measured. For this purpose, the respiratory patterns of 10 patients are obtained and simulated on an acrylic phantom - a model of the human body used to test the response of patients to different radiation treatments. An insert made to accommodate cell vials or radiation dosimeters is attached to the phantom body, and moves to mimic the breathing of the selected patient. Positive outcomes of the study could imply that respiratory-gated radiotherapy is the next step in improving liver cancer patient quality of life and survival.