Introduction: Gamma Knife Radiosurgery is an effective tool for metastatic brain tumors, both as a primary and adjuvant treatment methodology. In the setting of brainstem metastases, a harbinger of a poor prognosis, GKRS is a safe and effective tool to obtain local intracranial control and treat and/or prevent worsening of neurologic symptoms from brainstem mass effect. However, there isn't any significant current data to quantify the timeline and volume change effect of GKRS treatment of brainstem metastatic tumors. We set out to accomplish this.
Methods: After excluding patients without followup data or with incomplete results, we evaluated 36 patients with metastatic brainstem tumors undergoing GKRS at Roswell Park Cancer Institute since 2008. Using Leksell GammaPlan software we contoured each patient's tumor at initial diagnosis and subsequent follow up images. We then accumulated volume and interval time data as well as general demographics.
Results: of the 36 patients, average initial tumor volume was .795 cubic cm (range .0025 to 5.14). Average first follow up was 2.8 months (range .47 to 8.93), with average tumor reduction 65.45%, 9 patients reduced 100%. At 5.6 months, average volume reduction was 67.89%, 11 patients reduced 100%. At 7.94 months follow up, surviving patients reduced 80.77%. Of those that survived 11.67 months, average reduction was 88.2%.
Conclusions: GKRS is an effective primary treatment for brainstem metastases with our data exhibiting increased benefit over time and 25% of patients exhibiting a 100% reduction in tumor volume by 2.8 months, 30.5% by almost 6 months, and 88.2% reduction in those surviving almost 12 months. With novel treatments engendering improved systemic disease control, patients with brainstem metastases should be effectively treated at optimal but safe dosing regimens. With this data we can also quantify the effect of GK on brainstem metastases.
Patient Care: expounding on this data may allow us to give patients a general chronology of how this treatment method can affect their tumor in the present, near, and distant future, depending on their prognosis. This may allow for further autonomy for patients in selecting their treatment path, and may generate more optimism in the treatment.
Learning Objectives: By the conclusion of this session, participants should be able to understand the benefit of GKRS in brainstem metastases regardless of its effect on prognosis. Also, participants can generate a general idea of the quantified effect over time of GK on brainstem metastases. While at a dose often less than applied to cerebellar or supratentorial tumors of similar size, there is an excellent effect resulting a significant reduction in size of brainstem tumors, thus allowing symptoms of mass effect to resolve.