Keywords
Radiation Oncology; Laryngeal Cancer; Medicine; Cancer Therapy
Abstract
Purpose/Objective(s): Although early larynx cancers require treatment of only the vocal cord(s), radiation forearly larynx cancer historically consisted of opposed lateral portals that included the entire larynx. Treatmenttechniques have advanced to 3D conformal and intensity modulated radiotherapy (IMRT), but the treatment targethas remained the entire larynx. One concern preventing volume reduction in these patients is periodic swallowingthat occurs during treatment delivery due to normal patient physiology. Such intrafraction swallowing candisplace the treatment target up to 2 cm and could lead to tumor underdosing. Treatment with real-time targettracking could greatly mitigate this concern. Herein, we describe our initial experience using MR-guidedradiotherapy (MRgRT) to visualize and understand the impact of intrafraction larynx motion.Materials/Methods: Three patients with cT1-2 laryngeal cancer were treated using an MRgRT linac. Treatmentvolume included the entire larynx to evaluate feasibility of setup, immobilization, patient tracking, and treatmentplanning. A commercial MR-compatible head-and-heck immobilization system was developed and utilized,consisting of an indexable baseplate with integrated MR receiver coils affixed to a head cradle, with an open-facethermoplastic mask and head-mold cushion. Treatment plans were inversely planned utilizing 5 anterior IMRTfields to eliminate entrance dose to posterior organs at risk (OARs). The tracking structure consisted of patients’intrinsic larynx muscles delineated by a head and neck radiation oncologist on a 35cm x 35cm x 0.70cm sagittalMR plane. Patients were instructed not to swallow during setup imaging and during treatment. Continuous real-time tracking was performed at 4 frames per second with automatic beam hold if >5% of the area of the trackingstructure exceeded the 3mm isotropic boundary limit.Results: Images were taken during patient treatment, and movement of the intrinsic muscles of the larynx wasapparent in all patients due to periodic deglutition. At the time of analysis, 63 fractions have been delivered. Theaverage total in-room time for the three patients in the study was 27:22 minutes (range 18:00 - 45:00 minutes),while the average beam-on time was 8:44 minutes (range 4:00 - 30:00 minutes).Conclusion: MR real-time visualization of the patient’s intrinsic laryngeal muscles during MRgRT provides amethod of gating treatment during patient swallowing. Robust intrafraction target tracking appears to enablehigher confidence in reducing the treatment volume for early larynx cancers such that improvements inpreservation of voice quality and deglutition capabilities are possible without sacrificing local control. A clinicaltrial is planned to examine such volume reduction and its effect on patient quality of life and function.
Date Created
October 2021
STARS Citation
Autrey, Cody; Mittauer, Kathryn; Alvarez, Diane; Chuong, Michael; Contreras, Jessika; Gutierrez, Alonso; Kaiser, Adeel; McCulloch, James; Romaguera, Tino; and Kalman, Noah, "MR-Guided Radiotherapy (MRgRT) for Laryngeal Cancer With Real-time Visualization of Intrafraction Larynx Motion" (2021). EGS Content. 21.
https://stars.library.ucf.edu/egs_content/21
https://works.bepress.com/cody-autrey/9/download/