Two-staged gamma knife radiosurgery for treatment of numerous (>10) brain metastases

Novel radiotherapeutic strategies in the management of brain metastases: Challenging the dogma

The role of radiation therapy in the management of brain metastasis is evolving. Advancements in machine learning techniques have improved our ability to both detect brain metastasis and our ability to contour substructures of the brain as critical organs at risk. Advanced imaging with PET tracers and magnetic resonance imaging-based artificial intelligence models can now predict tumor control and differentiate tumor progression from radiation necrosis. These advancements will help to optimize dose and fractionation for each patient's lesion based on tumor size, histology, systemic therapy, medical comorbidities/patient genetics, and tumor molecular features. This review will discuss the current state of brain directed radiation for brain metastasis. We will also discuss future directions to improve the precision of stereotactic radiosurgery and optimize whole brain radiation techniques to improve local tumor control and prevent cognitive decline without forming necrosis.

Is Gamma Knife surgery, omitting adjunct whole brain radiation treatment, feasible for patients with 20 or more brain metastases?

Background

The importance of the number of brain metastases (BM) when deciding between whole brain radiation treatment (WBRT) and radiosurgery is controversial. We hypothesized that the number of BM is of limited importance when deciding radiation strategy, and offered Gamma Knife surgery (GKS) also for selected patients with 20 or more BM.

Methods

The outcome following single session GKS for 75 consecutive patients harboring 20 or more (20+) BM was analyzed. Data was collected both retro- and prospectively.

Results

The median survival time was 9 months. Two grade 3 complications occurred, 1 resolved and 1 did not. Sex and clinical condition at the time of GKS (ECOG value) were the only parameters significantly related to survival time. Eighteen patients developed leptomeningeal dissemination with or without distant recurrences (DR), and another 32 patients developed DR a total of 73 times. DR was managed with GKS 24 times, with WBRT 3 times and with systemic treatment or best supportive care 46 times. The median time to developing DR was unrelated to the number of BM, but significantly longer for patients older than 65 years, as well as for patients with NSCLC.

Conclusions

GKS is a reasonable treatment option for selected patients with 20 or more BM. It is better to decide the optimal management of post-GKS intracranial disease progression once it occurs rather than trying to prevent it by using adjunct WBRT.

Evaluation of Biological Effective Dose in Gamma Knife Staged Stereotactic Radiosurgery for Large Brain Metastases

Objective

Gamma knife (GK) staged stereotactic radiosurgery (Staged-SRS) has become an effective treatment option for large brain metastases (BMs); however, it has been challenging to evaluate the total dose because of tumor shrinkage between two staged sessions. This study aims to evaluate total biological effective dose (BED) in Staged-SRS, and to compare the BED with those in single-fraction SRS (SF-SRS) and hypo-fractionated SRS (HF-SRS).

Methods

Patients treated with GK Staged-SRS at a single institution were retrospectively included. The dose delivered in two sessions of Staged-SRS was summed using the deformable image registration. Each patient was replanned for SF-SRS and HF-SRS. The total BEDs were computed using the linear-quadratic model. Tumor BED_98% and brain V_84Gy2, equivalent to V_12Gy in SF-SRS, were compared between SF-SRS, HF-SRS, and Staged-SRS plans with the Wilcoxon test.

Results

Twelve patients with 24 BMs treated with GK Staged-SRS were identified. We observed significant differences (p < 0.05) in tumor BED_98% but comparable brain V_84Gy2 (p = 0.677) between the Staged-SRS and SF-SRS plans. No dosimetric advantages of Staged-SRS over HF-SRS were observed. Tumor BED_98% in the HF-SRS plans were significantly higher than those in the Staged-SRS plans (p < 0.05). Despite the larger PTVs, brain V_84Gy2 in the HF-SRS plans remained lower (p < 0.05).

Conclusion

We presented an approach to calculate the composite BEDs delivered to both tumor and normal brain tissue in Staged-SRS. Compared to SF-SRS, Staged-SRS delivers a higher dose to tumor but maintains a comparable dose to normal brain tissue. Our results did not show any dosimetric advantages of Staged-SRS over HF-SRS.

Clinical outcomes of patients with multiple courses of radiosurgery for brain metastases from non-small cell lung cancer

We investigated the long-term clinical outcomes of patients who underwent multiple courses (≥ 5) of gamma knife radiosurgery (GKRS) due to recurrent brain metastases (BM) from non-small cell lung cancer (NSCLC). Between December 2001 and July 2019, consecutive 2571 patients underwent GKRS for BM from NSCLC. Clinical and radiological outcomes were investigated in 76 patients who underwent GKRS ≥ 5 times. The median follow-up period after the diagnosis of NSCLC was 54.6 months (range 14.5–159.1 months). The median number of GKRS procedures per patient was six (range 5–15). Actuarial post-GKRS survival rates at 1, 2, 3, 4, and 5 years following initial GKRS were 88.1%, 79.5%, 65.3%, 51.4%, and 37.3%, respectively. No significant difference in overall survival was observed between patients (n = 22) with whole-brain radiotherapy (WBRT) and patients (n = 54) without WBRT (p = 0.076). The incidence of radiation-induced leukoencephalopathy was 64% and 18% in patients with and without WBRT, respectively (p < 0.0001). Multiple courses of SRS are a tolerable and effective treatment option for recurrent BM from NSCLC. Repeat SRS may be an alternative treatment option to avoid or delay WBRT.

Metastatic Neoplasm Volume Kinetics Following Two-Staged Stereotactic Radiosurgery

INTRODUCTION

Multisession staged stereotactic radiosurgery (2-SSRS) represents an alternative approach for management of large brain metastases (LBMs), with potential advantages over fractionated SRS. We investigated the clinical efficacy and safety of 2-SSRS in patients with LBMs.

METHODS

LBMs patients treated with 2-SSRS between 2014-2020 were evaluated. Demographic, clinical, and radiologic information was obtained. Volumetric measurements at first SSRS, second SSRS, and follow-up imaging studies were obtained. Characteristics that might predict response to 2-SSRS were evaluated through Fischer-exact or Mann-Whitney U test.

RESULTS

Twenty-four patients with 26 LBMs were included in the study. Median marginal doses for first and second SSRS were 15 Gy (14-18 Gy) and 15 Gy (12-16 Gy), respectively. Median tumor volumes at first SSRS, second SSRS, and 3-month follow-up were 8.1 cm³ (1.5-28.5 cm³), 3.3 cm³ (0.8-26.1 cm³), and 2.2 cm³ (0.2-10.1 cm³), respectively. Overall, 24/26 lesions (92%) demonstrated early local control following the first SSRS with 17 lesions (71%) demonstrating a decrease of >30% in the T1 post-contrast MRI volume before the second SSRS and 3 lesions (12%) remaining stable. Eventually, four lesions showed disease progression after 2-SSRS. The median time to local progression was not reached and the median time to intracranial progression was 9.1 months.

CONCLUSIONS

Our study supports the effectiveness and safety of 2-SSRS as a treatment modality for patients with large, symptomatic brain metastases, especially in poor surgical candidates. The local failure rate and low occurrence of adverse effects are comparable to other staged radiosurgery studies.