All accrued participants will be enrolled onto the MRIdian Linac Group. Participants will receive adaptive radiotherapy (ART) on the MRIdian Linac. Participants will complete the duration of their radiotherapy regimen on the MRIdian Linac for approximately 7 weeks.

Radiation therapy (RT) will be delivered with an integrated MRI-RT delivery system (MRIdian Linac). Participants will then receive standard-of-care RT with a dose prescription of 70 Gy in 35 fractions on the MRIdian Linac. Adaptive RT (ART) planning will occur every 5th fraction of RT.

Weekly adaptive plans will be compared to the initial reference plan and compared using a percent difference equation estimating the actual values of the quantities used as dosimetric constraints for each participant between the initial reference plan and the weekly adaptive plan[s].

For evaluation of deformable imaging registration, deformed contours will be compared to the physician-segmented contours using the Dice similarity coefficient (DSC).

We will follow previously-established guidelines by the MR-Linac Consortium Head and Neck Tumor Site for measuring treatment times. Treatment times will be calculated in minutes from the time stamps in the record and verify system. Three timepoints will be recorded: [1] setup and plan optimization [i.e. time between the participant's arrival to the MRidian and delivery of the first beam]; [2] beam delivery [i.e. the time between delivery of the first and last beam]; and [3] total treatment time.