Multi-institutional experience of MR-guided stereotactic body radiation therapy for adrenal gland metastases

Matthew Mills; Rupesh Kotecha; Roberto Herrera; Tugce Kutuk; Matthew Fahey; Evan Wuthrick; G Daniel Grass; Sarah Hoffe; Jessica Frakes; Michael D Chuong; Stephen A Rosenberg

doi:10.1016/j.ctro.2023.100719

Multi-institutional experience of MR-guided stereotactic body radiation therapy for adrenal gland metastases

Clin Transl Radiat Oncol. 2024 Jan 5:45:100719. doi: 10.1016/j.ctro.2023.100719. eCollection 2024 Mar.

Affiliations

¹ Department of Radiation Oncology, Moffitt Cancer Center, Tampa, FL, United States.
² Department of Radiation Oncology, Miami Cancer Institute, Baptist Health South Florida, Miami, FL, United States.
³ University of South Florida Morsani College of Medicine, Tampa, FL, United States.

Abstract

Purpose: While dose escalation is associated with improved local control (LC) for adrenal gland metastases (AGMs), the proximity of gastrointestinal (GI) organs-at-risk (OARs) limits the dose that can be safely prescribed via CT-based stereotactic body radiation therapy (SBRT). The advantages of magnetic resonance-guided SBRT (MRgSBRT), including tumor tracking and online plan adaptation, facilitate safe dose escalation.

Methods: This is a multi-institutional review of 57 consecutive patients who received MRgSBRT on a 0.35-T MR linac to 61 AGMs from 2019 to 2021. The Kaplan-Meier method was used to estimate overall survival (OS), progression-free survival (PFS), and LC, and the Cox proportional hazards model was utilized for univariate analysis (UVA).

Results: Median follow up from MRgSBRT was 16.4 months (range [R]: 1.1-39 months). Median age was 67 years (R: 28-84 years). Primary histologies included non-small cell lung cancer (N = 38), renal cell carcinoma (N = 6), and melanoma (N = 5), amongst others. The median maximum diameter was 2.7 cm (R: 0.6-7.6 cm), and most AGMs were left-sided (N = 32). The median dose was 50 Gy (R: 30-60 Gy) in 5-10 fractions with a median BED₁₀ of 100 Gy (R: 48-132 Gy). 45 cases (74 %) required adaptation for at least 1 fraction (median: 4 fractions, R: 0-10). Left-sided AGMs required adaptation in at least 1 fraction more frequently than right-sided AGMs (88 % vs 59 %, p = 0.018). There were 3 cases of reirradiation, including 60 Gy in 10 fractions (N = 1) and 40 Gy in 5 fractions (N = 2). One-year LC, PFS, and OS were 92 %, 52 %, and 78 %, respectively. On UVA, melanoma histology predicted for inferior 1-year LC (80 % vs 93 %, p = 0.012). There were no instances of grade 3+ toxicity.

Conclusions: We demonstrate that MRgSBRT achieves favorable early LC and no grade 3 + toxicity despite prescribing a median BED₁₀ of 100 Gy to targets near GI OARs.

Keywords: Adrenal gland metastasis; MR-guided radiation therapy; Oligometastasis; Stereotactic body radiation therapy.