# Re-irradiation of adrenal metastases using MR-guided adaptive SABR: A feasible and effective approach in a high-risk population

## TL;DR

Using MR-guided SABR, re-irradiation of adrenal metastases is shown to be feasible and effective with minimal side effects in high-risk patients.

## Contribution

First report of ablative-dose MR-guided adaptive re-SABR for adrenal metastases with real-time imaging and dose adaptation.

## Key findings

- Six of seven patients remained progression-free with a median follow-up of 8.6 months.
- Treatment caused no grade ≥3 toxicities, only minor side effects like vertebral fracture and nausea.

## Abstract

•Local recurrence after SABR for adrenal metastasis is challenging.•First report of ablative-dose re-SABR (5 × 10  Gy or 3 × 15  Gy) in this setting.•Six of seven patients were progression-free at median 8.6 months follow-up.•No grade ≥ 3 toxicities; only one grade 2 vertebral fracture and one grade 1 nausea.•MR-guided adaptive re-SABR provides a tolerable, non-invasive, high-precision treatment option.

Local recurrence after SABR for adrenal metastasis is challenging.

First report of ablative-dose re-SABR (5 × 10  Gy or 3 × 15  Gy) in this setting.

Six of seven patients were progression-free at median 8.6 months follow-up.

No grade ≥ 3 toxicities; only one grade 2 vertebral fracture and one grade 1 nausea.

MR-guided adaptive re-SABR provides a tolerable, non-invasive, high-precision treatment option.

Re-irradiation of adrenal metastases is challenging due to cumulative dose constraints. We present seven patients treated with MR-guided adaptive stereotactic ablative radiotherapy (SABR), leveraging real-time imaging and on-table adaptation for precise dose delivery (5× 10 Gy or 3× 15 Gy). This first report of ablative-dose MR-guided SABR in re-irradiation demonstrates excellent local control and acceptable toxicity, with six patients progression-free at median 8.6 months and no grade ≥3 events (one grade 2 vertebral fracture, one grade 1 nausea). By providing a non-invasive alternative to surgery or palliative radiotherapy, MR-guided adaptive SABR expands therapeutic options for high-risk patients.