Clinical Implementation and Initial Experience With a 1.5 Tesla MR-Linac for MR-Guided Radiation Therapy for Gynecologic Cancer: An R-IDEAL Stage 1 and 2a First in Humans Feasibility Study of New Technology Implementation

Authors

David S Lakomy
Jinzhong Yang
Sastry Vedam
Jihong Wang
Belinda Lee
Angela Sobremonte
Pamela Castillo
Neil Hughes
Mustefa Mohammedsaid
Anuja Jhingran
Ann H Klopp
Seungtaek Choi
C David Fuller
Lilie L Lin

Publication Date

1-1-2022

Journal

Practical Radiation Oncology

Abstract

PURPOSE: Magnetic resonance imaging-guided linear accelerator systems (MR-linacs) can facilitate the daily adaptation of radiation therapy plans. Here, we report our early clinical experience using a MR-linac for adaptive radiation therapy of gynecologic malignancies.

METHODS AND MATERIALS: Treatments were planned with an Elekta Monaco v5.4.01 and delivered by a 1.5 Tesla Elekta Unity MR-linac. The system offers a choice of daily adaptation based on either position (ATP) or shape (ATS) of the tumor and surrounding normal structures. The ATS approach has the option of manually editing the contours of tumors and surrounding normal structures before the plan is adapted. Here, we documented the duration of each treatment fraction; set-up variability (assessed by isocenter shifts in each plan) between fractions; and, for quality assurance, calculated the percentage of plans meeting the γ-criterion of 3%/3-mm distance to agreement. Deformable accumulated dose calculations were used to compare accumulated versus planned dose for patient treated with exclusively ATP fractions.

RESULTS: Of the 10 patients treated with 90 fractions on the MR-linac, most received boost doses to recurrence in nodes or isolated tumors. Each treatment fraction lasted a median 32 minutes; fractions were shorter with ATP than with ATS (30 min vs 42 min, P < .0001). The γ criterion for all fraction plans exceeded >90% (median, 99.9%; range, 92.4%-100%; ie, all plans passed quality assurance testing). The average extent of isocenter shift was < 0.5 cm in each axis. The accumulated dose to the gross tumor volume was within 5% of the reference plan for all ATP cases. Accumulated doses for lesions in the pelvic periphery were within < 1% of the reference plan as opposed to -1.6% to -4.4% for central pelvic tumors.

CONCLUSIONS: The MR-linac is a reliable and clinically feasible tool for treating patients with gynecologic cancer.

Keywords

Adenosine Triphosphate, Feasibility Studies, Female, Genital Neoplasms, Female, Humans, Magnetic Resonance Imaging, Particle Accelerators, Radiotherapy Dosage, Radiotherapy Planning, Computer-Assisted, Technology

DOI

10.1016/j.prro.2022.03.002

PMID

35278717

PMCID

PMC9233002

PubMedCentral® Posted Date

7-1-2023

PubMedCentral® Full Text Version

Author MSS

Published Open-Access

yes