Palliative Expeditiously Adaptive Quad Shot Radiation Therapy (PEAQ-RT): A Pilot Study of Consolidated Simulation and Target Identification of Quad Shot Radiation Using an Adaptive Radiotherapy Workflow

Purpose: This is a pilot study evaluating the feasibility of using the novel CBCT-guided Ethos system to deliver adaptive, expedited Quad shot radiation for patients with head and neck cancers.

Methodology: Consenting and eligible patients underwent standard CT simulation to plan the first cycle of Quad shot radiation at 3.5 Gy BID on two consecutive days. On the first day of Cycle 1 of Quad shot, the patient will undergo Ethos CBCT imaging. These images will be reviewed by a radiation oncologist to determine if the GTV and PTV are adequately visualized, if the treatment plan adequately covers the target volumes, and if there is any need to adapt the treatment plan prior to proceeding with Fraction 1 of Cycle 1 of Quad shot.

After completion of Cycle 1 of Quad shot, the patient will follow-up in 3 to 4 weeks to determine whether an additional cycle of Quad shot will take place. If it is, the patient will undergo a CBCT on the Ethos treatment machine followed by the first fraction of Quad shot on the same day. Standard CT simulation will be omitted for Cycle 2. Prior to delivery of Fraction 1 of Cycle 2, a radiation oncologist will review the CBCT images to determine if the GTV and PTV are adequately visualized, if the existing treatment plan adequately covers the target volumes, and if there is any need to adapt the treatment plan prior to proceeding with Fraction 1 of Cycle 2 of Quad shot. If it is not possible to identify the GTV and PTV on the Ethos CBCT imaging, or if the adapted and scheduled plans are considered unacceptable by the physician, the patient will be taken for a standard CT simulation for replanning of Cycle 2 of Quad shot. The same process will be followed for Cycle 3 of Quad shot if applicable.

Results: Thus far we have accrued 1 patient to this study since opening. This patient was treated for painful neck lymphadenopathy and primary supraglottic laryngeal recurrence causing dysphagia/odynophagia. She underwent cycle 1 of Quadshot and tolerated treatment well. She then underwent CBCT simulation in lieu of CT simulation for cycle 2. Adaptation was necessary due to tumor growth in the interim between cycles 1 and 2 of Quad shot. CBCT quality allowed for accurate target delineation and organs at risk delineation by treating MD. Study remains open with continuing accrual

Conclusions: CBCT guided simulation is feasible as we continue to accrue to this open trial to deliver Quad shot in an expedited manner.

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