Management of critically located brain metastases in patients with precluded survival using customised double-dose prescription-based, adaptive accelerated staged radiosurgery: a long-term retrospective analysis.

Background: Patients with brain metastases face a poor prognosis when deemed not to be suitable for onco-surgical intervention. This feasibility study analyses the outcome of adaptive radiosurgery applied in customised settings to a group of patients with brain metastases, where no other form of treatment was deemed safe and/or feasible.

Methods: 29 patients with 35 brain metastases deemed not to be candidates for surgery, radiotherapy or systemic treatment were treated with MRI-guided adaptive Gamma Knife radiosurgery in 3 separate sessions with a 72-hour interval. Customised synchronous double-dose prescriptions were systematically utilised at each session. Estimated survival at pre-treatment was fewer than 4 weeks due to the targeted intracranial lesions. A retrospective analysis was conducted on the whole cohort, with particular emphasis on those surviving 12 months and beyond.

Results: The median overall survival was 7.3 months, with a follow-up of 7.5 years. Survival at 6, 12, 24, 36, 48 and 60 months was 62%, 41%, 17%, 14%, 10% and 7%, respectively. Local tumour control (LTC) at 1 year was 75%. 4 patients developed local recurrence late on follow-up, with a survival ranging between 12 and 40 months. 2 patients were alive at the time of submission (115- and 117-months post-treatment) with no sequelae; the remainder succumbed to general disease progression, with neurologic death being avoided throughout the whole cohort. Adverse radiation effects (ARE) were reported in 5 patients, of which 4 remained asymptomatic throughout follow-up.

Conclusions: Based on the results of this first retrospective study, adaptive radiosurgery in double-dose prescription settings provided acceptable rates of LTC and ARE despite the underlying accelerated timeline, ultimately preventing neurologic death in a group of patients with an extremely poor prognosis. Prospective studies involving a larger number of patients with homogenous histology are warranted to validate the results of this study and optimise the technique.