MRI-guided Real-time Online Gated Stereotactic Body Radiation Therapy for Liver Tumors

Background: Liver tumors are commonly encountered in oncology. The study aimed to assess the impact of magnetic resonance imaging (MRI)-guided stereotactic body radiation therapy (SBRT) (MRgSBRT) on disease-related outcomes and the toxicity profile. Methods: Patients who received MRgSBRT from 2019 to 2021 for primary and metastatic liver tumors were included in this analysis. The protocol for treatment simulation included Gadoxetate disodium injection followed by a single-dimensional post-exhale MRI (0.35-T MRI linear accelerator) and computed tomography simulation. The patient demographics and treatment-related outcomes were assessed. The time-to-event curves were analyzed for freedom from local progression (FFLP) and overall survival (OS). Results: A total of 35 patients were eligible for analysis with a median age of 70 years (range 25 to 95). The median follow-up was 19.4 months (range 1 to 37 mo). The one-year OS was 77.7%, with an estimated 3 years of 47.9%. Patients with the locally controlled disease had a better median OS of 27.8 months (95% CI [23.8-31.6]) compared with 13.5 months (95% CI [5.6-21.3], P=0.007) in patients with local disease progression. The 1-year FFLP was 95.6%, and 3-year estimated FFLP was 87.1%. Patients who received a radiation dose of biologically equivalent dose≥100 Gy had FFLP of 30.9 months (95% CI [28.7-33.1]) compared with 13.3 months (95% CI [5.3-21.3], P=0.004) in patients who received <100 Gy biologically equivalent dose. Conclusion: MRI-guided SBRT provides optimal local control, associated with improved OS in a heavily morbid, pretreated older cohort of patients with reasonable safety profiles.