Introduction: Brainstem metastases offer a unique challenge in treatment, yet stereotactic radiosurgery (SRS) has proven to be an effective modality in treating these tumors. Our purpose was to report on the clinical outcomes of patients treated at our institution with Gamma Knife radiosurgery.
Methods: Patients with tumors metastatic to brainstem from 2008-2016 were analyzed. Nineteen (19) brainstem metastases from 14 patients who had follow-up brain imaging were identified. Patient and tumor characteristics, SRS parameters, local control, overall survival, and toxicity were assessed.
Results: Median tumor volume was 0.04 cc (range 0.007-2.03 cc). Whole brain radiation therapy was administered before SRS in 35.7% of patients and after in 7.1% of patients. Median prescribed dose was 17.5 Gy to the 50% isodose line (range 14-22 Gy). Median max dose was 33 Gy (range 23.4-39.3 Gy) and median minimum dose was 18.2 Gy (range 13.8-30.6 Gy). Median survival after GK SRS treatment to brainstem lesion was 17.2 months (range 2.8-45.57 months) with 6, 9, and 12 months survival being 92.9%, 85.7%, and 69.3%, respectively. Local control at 6, 9, and 12 months was 100%, 93.8%, and 87.5%, respectively. One pons lesion, 0.2 cc, was treated with 20 Gy to 51% isodose line with last follow up imaging at 10 months and another pons lesion, 0.04 cc, with 22 Gy to 60% isodose line with last follow up imaging at 7.5 months, neither of which exhibited any toxicity.
Conclusions: Our institutional experience reports on the safety and efficacy of a range of GK SRS prescription doses (14-22 Gy) to brainstem metastases. We found no significant toxicities associated with these doses and improved local control and overall survival compared to prior studies. Our data imply value in prospectively evaluating local control and toxicity with higher margin doses than previously thought safe for brainstem metastases treated with GK SRS.
Patient Care: Have more data available to better balance the trade off between local toxicity, local control, and overall survival when it comes to treating brainstem metastases with stereotactic radiosurgery.
Learning Objectives: By the conclusion of this session, participants should be able to:
1) Understand the safety and efficacy of stereotactic radiosurgery in the brainstem.
2) Understand that relatively higher doses can be used in treating brainstem metastatic lesions that results in excellent local control and modest survival.
3) Understand that relatively higher doses than historically thought can be used in treating brainstem metastatic lesions with minimal toxicity.