Authors: Alonso La Rosa, MD^∗, Kathryn E. Mittauer, PhD^∗,†, Michael D. Chuong, MD^∗,†, Matthew D. Hall, MD, MBA^∗,†, Tugce Kutuk, MD^∗, Nema Bassiri, PhD^∗, James McCulloch, DMP ^∗, Diane Alvarez, MSc ^∗, Robert Herrera, BS^∗, Alonso N. Gutierrez, PhD, MBA^∗,†, Ranjini Tolakanahalli, PhD^∗,†, Minesh P. Mehta, MD^∗,†, Rupesh Kotecha, MD^∗,†,‡,

^∗ Department of Radiation Oncology, Miami Cancer Institute, Baptist Health South Florida, Miami, FL, USA
^† Department of Radiation Oncology, Herbert Wertheim College of Medicine, Florida International University, Miami, FL, USA
^‡ Department of Translational Medicine, Herbert Wertheim College of Medicine, Florida International University, Miami, FL, USA

Given the positive results from recent randomized controlled trials in patients with oligometastatic, oligoprogressive, or oligoresidual disease, the role of radiotherapy has expanded in patients with metastatic non-small cell lung cancer (NSCLC). While small metastatic lesions are commonly treated with stereotactic body radiotherapy (SBRT), treatment of the primary tumor and involved regional lymph nodes may require prolonged fractionation schedules to ensure safety especially when treating larger volumes in proximity to critical organs-at-risk (OARs). We have developed an institutional MR-guided adaptive radiotherapy (MRgRT) work?ow for these patients. We present a 71-year-old patient with stage IV NSCLC with oligoprogression of the primary tumor and associated regional lymph nodes in which MR-guided, online adaptive radiotherapy was performed, prescribing 60 Gy in 15 fractions. We describe our work- ?ow, dosimetric constraints, and daily dosimetric comparisons for the critical OARs (esophagus, trachea, and proximal bronchial tree [PBT] maximum doses [D0.03cc]), in comparison to the original treatment plan recalculated on the anatomy of the day (i.e., predicted doses). During MRgRT, few fractions met the original dosimetric objectives: 6.6% for esophagus, 6.6% for PBT, and 6.6% for trachea. Online adaptive radiotherapy reduced the cumulative doses to the structures by 11.34%, 4.2%, and 5.62% when comparing predicted plan summations to the ?nal delivered summation. Therefore, this case study presets a work- ?ow and treatment paradigm for accelerated hypofractionated MRgRT due to the signi?cant variations in daily dose to the central thoracic OARs to reduce treatment-related toxicity associated with radiotherapy.

As of January 1, 2022, ARRT requires CE Credits for Directed Journal Readings to be based on the word count for each article. So, the number of CE Credits for each DJR article will vary for ARRT. For this article, the ARRT CE Credit will be 0.75 Credit. The MDCB CE Credits will remain at 2.5 Credits.