Outcomes and Toxicities of Stereotactic Radiosurgery for Large Brainstem Metastases

Document Type

Conference Proceeding

Publication Date

10-2024

Publication Title

International Journal of Radiation Oncology, Biology, Physics

Abstract

Purpose/Objective(s): Brainstem metastases (BSM) are associated with a poor prognosis and limited management options. Multiple studies have shown the safety and efficacy of stereotactic radiosurgery (SRS) for predominantly small BSM (<1cc). SRS to larger volumes have been associated with increased risk of toxicity. This study aims to evaluate the safety and efficacy of SRS for large (>1cc) brainstem metastases. Materials/Methods: We identified 131 patients with 157 BSM consecutively treated with SRS in a single institution from 2008 to 2024. The median tumor volume was 0.06cc (IQR 0.028 to 0.28cc) and 24 patients with 24 BSM >1cc were extracted for this analysis. Local control (LC), overall survival (OS), symptomatic improvement and toxicity (graded by the Common Terminology Criteria for Adverse Events v4.0) were evaluated. Univariable and multivariable Cox regression analyses were performed to determine association of outcomes with various clinical and dosimetric parameters. Results: The median age of patients was 63 years (range = 49-85 years). The primary diagnoses were 17 cases of lung cancer (one small-cell), 3 breast cancer, 2 gastrointestinal, 1 renal cell, and 1 unknown primary. Seven lesions were located in the midbrain with 17 in the pons. The median treated tumor volume was 1.4 cc (range = 1.1 − 3.2 cc); the median maximum linear tumor dimension was 1.7 cm (range = 1.4 cm to 3.2 cm). Twenty-one tumors (88%) were treated in a single fraction with a median marginal dose of 13 Gy (range = 10 - 16 Gy) to a median isodose line (IDL) of 50%. Three patients with tumor volume of 1.6 − 3.2 cc were treated in 3 fractions to marginal doses of 21 - 25 Gy to the 45 - 57% IDLs. The median conformality index was 2.6 (range = 0.98 to 5.35). Thirteen patients (54%) underwent whole brain radiation therapy − 11 prior to, and 2 after BSM SRS. In the 18 patients with at least one post-SRS brain MRI, no local failure was reported. The median OS was 4.2 months with 1 year OS of 16.7% after SRS. Active extracranial disease (HR = 5.41, 95% CI = 1.56-18.8, P<0.01) and larger maximum linear tumor dimension (HR = 4.34, 95% CI = 1.12-16.7, P = 0.03) were associated with worse overall survival on multivariable analysis. Seventeen patients (74%) had at least one symptom attributed to their BSM which included cranial nerve (CN) deficits in 10 patients (42%), long tract symptoms in 9 patients (38%) and cerebellar signs in 3 patients. There was clinical improvement in neurological symptoms in 12 of 17 (71%) symptomatic patients. A total of 4 patients (24%) had any SRS related toxicity with two (12%) grade 1 toxicity of nausea/ vomiting and motor weakness, one (5.9%) grade 2 CN deficit and one (5.9%) grade 3 aphasia. There was no radiation necrosis or grade 4-5 toxicity. Conclusion: The results of our study show that SRS to relatively large brainstem metastases is a reasonably safe and effective local therapy with a high likelihood of improvement in neurological symptoms.

Volume

120

Issue

2S

First Page

e263

Last Page

e264

Comments

ASTRO 2024: 66th Annual Meeting American Society for Radiation Oncology, September 29 - October 2, 2024, Washington, DC

DOI

10.1016/j.ijrobp.2024.07.589

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