MRI-guided radiotherapy for head and neck cancer: initial clinical experience

To report a single-institutional experience with the use of magnetic resonance imaging (MRI)-guided radiotherapy for cancers of the head and neck. Between October 2014 and October 2016, 18 patients with newly diagnosed cancers of the head and neck were prospectively enrolled on an institutional registry trial investigating the feasibility and efficacy of external-beam radiotherapy delivered using on-board MRI. All patients had biopsy-proven evidence of malignancy, measurable disease, and the ability to provide consent. None had previously received any treatment. Median dose was 70 Gy (range 54-70 Gy). MRI scans were obtained as part of an image-guided registration protocol for alignment prior to and during each treatment. Concurrent chemotherapy was administered to 14 patients (78%). Patient-reported outcomes were assessed using the University of Washington quality of life instrument. Seventeen of 18 patients completed the planned intensity-modulated radiotherapy (IMRT) treatment of which 15 (83%) had a complete response and 2 (11%) had a partial response based on initial post-therapy positron emission tomography (PET) at 3 months. The 1-year estimates of progression-free survival, overall survival, and local-regional control were 95, 96, and 95%, respectively. There were no treatment-related fatalities. The incidence of grade 3+ acute toxicity was 44%. The proportion of patients rating their health-related quality of life as "very good" or "outstanding" at 6 months and 1 year after completion of radiation therapy was 60 and 70%, respectively. MRI-guided radiotherapy achieves clinical outcomes comparable to contemporary series reporting on IMRT for head and neck cancer.