Advances in Radiation Oncology (Mar 2022)

Dose-Escalated Magnetic Resonance Image–Guided Abdominopelvic Reirradiation With Continuous Intrafraction Visualization, Soft Tissue Tracking, and Automatic Beam Gating

  • Michael D. Chuong, MD,
  • John M. Bryant, MD,
  • Roberto Herrera, BS,
  • James McCulloch, DMP,
  • Jessika Contreras, MD,
  • Rupesh Kotecha, MD,
  • Tino Romaguera, PhD,
  • Diane Alvarez, MSc,
  • Matthew D. Hall, MD, MBA,
  • Muni Rubens, MBBS, MPH, PhD,
  • Minesh P. Mehta, MD,
  • Adeel Kaiser, MD,
  • Martin Tom, MD,
  • Alonso N. Gutierrez, PhD, MBA,
  • Kathryn E. Mittauer, PhD

Journal volume & issue
Vol. 7, no. 2
p. 100840

Abstract

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Purpose: Compared with computed tomography, magnetic resonance (MR) image guidance offers significant advantages for radiation therapy (RT) that may be particularly beneficial for reirradiation (reRT). However, clinical outcomes of MR-guided reRT are not well described in the published literature. Methods and Materials: We performed a single-institution retrospective safety and efficacy analysis of reRT patients treated on the MRIdian Linac to targets within the abdomen or pelvis using continuous intrafraction MR-based motion management with automatic beam triggering. Fiducial markers were not used. Results: We evaluated 11 patients who received prior RT to a median of 50 Gy (range, 30-58.8 Gy) in 25 fractions (range, 5-28 fractions). The median interval to reRT was 26.8 months. The most frequently retreated sites were nodal metastases (36.4%) and pancreatic cancer (27.3%). The median reRT dose was 40 Gy (range, 25-54 Gy) in 6 fractions (range, 5-36 fractions); ultrahypofractionation (63.6%) was more common than hyperfractionation (36.4%). Daily on-table adaptive replanning was used for 3 patients (27.3%). With a median of 14 months’ follow-up from reRT completion (range, 6-32 months), the median and 1-year freedom from local progression were 29 months and 88.9%, respectively, and the median and 1-year overall survival were 17.5 months and 70.0%, respectively. One patient (9.1%) experienced acute grade 2 toxic effects; there were no acute or late treatment-related toxic effects of grade 3 or greater. Conclusions: Magnetic resonance–guided reRT appeared to be feasible and may facilitate safe dose escalation. Additional follow-up is needed to better assess long-term efficacy and late toxic effects. Prospective evaluation of this novel treatment strategy is warranted.