Session Item

Retrospective reports of preoperative radiosurgery for brain metastases (BMs) describe high efficacy with minimal toxicity. We present an interim analysis of a feasibility trial of radiosurgery prior to neurosurgical resection of a BM.

Eligibility criteria included: a BM up to 4 cm in diameter and up to three other BMs for radiosurgery, anticipated gross tumour resection, an estimated prognosis of at least six months and no contraindication to steroids or MRI. The date for elective neurosurgical resection was set following the tumour board and single fraction radiosurgery could be delivered up to and including the day of surgery. BMs were contoured on a 1.5T planning T1_Gd VIBE MRI and a 1mm planning  treatment margin was added. The single fraction dose was prescribed according to PTV volume and prescribed to cover 99% of the PTV with a maximum dose between 125% and 143%. Treatment plans were generated using Elements Cranial SRS v1.5 and v3.0 (Brainlab, Germany). Treatment was delivered on a Truebeam STx linac using the Novalis Radiosurgery platform (Brainlab/Varian, USA). Patients completed EORTC QLQ-C30 and BN20 quality of life questionnaires at 0,3,6,9 and 12 months. An exploratory endpoint was the evaluation of any difference in expression of proliferative, histiocytic and immune cell markers between the primary tumours and the BMs.

Twelve patients of median age 65 years (41-77) were recruited between 11/2020 and 02/2022. 3/12 had synchronous BMs. Seven patients had a single BM, four had two BMs, and one had three BMs. 11/12 patients received preoperative radiosurgery and metastasectomy as intended. The twelfth patient went directly to surgery and received postoperative fractionated stereotactic radiotherapy (fSRT). The median time between referral and radiosurgery was 5.5 working days (1-10) and neurosurgery took place a median of 1 day later (0-5), thus the median time from tumour board to metastasectomy was 7.5 working days (2-10). The median encompassing dose was 16 Gy (14-19), median GTV was 9.6 cm3 (7.0-21.5) and median PTV was 12.7 cm3 (5.9-26.1). 5/11 patients who received preoperative radiosurgery have completed 12 month follow-up without local recurrence or leptomeningeal disease. There was one acute related toxicity (grade 2 alopecia) at 3 months which recovered fully by 6 months, and seven patients have died from extracranial causes. The patient who received postoperative fSRT developed a small leptomeningeal recurrence 3 months after metastasectomy.  

Preoperative SRS was feasible in 11/12 patients and safe in 11/11 patients. This protocol constitutes the experimental arm of an open, international randomised trial to compare the efficacy of preoperative radiosurgery against postoperative hypofractionated stereotactic radiotherapy (PREOP-2, NCT05124236).