Clinical and radiographic adverse events after Gamma Knife radiosurgery for brainstem lesions: A dosimetric analysis

Objectives: To analyze the association between dosvolume relationships and adverse events in brainstem lesions treated with Gamma Knife radiosurgery (GKRS). Methods: Treatment plans were generated on BrainLab Elements and GammaPlan software. Dosimetric data were analyzed as continuous variables for patients who received GKRS to brain metastases or arteriovenous malformations (AVM) within or abutting the brainstem. Adverse events were classified as clinical and/or radiographic. Logistic and cox regression were used to assess the relationship between dosimetric variables and adverse events. Results: Sixty-one patients who underwent single fraction GKRS for brain metastases or AVM were retrospectively analyzed. Median age was 62 years (range: 12–92 years) and the median prescription dose was 18 Gy (range: 13–25 Gy). Median follow-up was 6months. Clinical and radiographic complications were seen in ten (16.4%) and 17 (27.9%) patients, respectively. On logistic regression, increasing D_05% was found to be associated with an increased probability of developing a clinical complication post-GKRS (OR: 1.18; 95% CI: 1.01–1.39; p = 0.04). Furthermore, mean brainstem dose (HR: 1.43; 95% CI: 1.05–1.94; p < 0.02), D_05% (HR: 1.09; 95% CI: 1.01–1.18; p = 0.03), and D_95% (HR: 2.37; 95% CI: 0.99–5.67; p = 0.05) were associated with an increased hazard of experiencing post-GKRS complications over time. Conclusions: Increasing D_05% to the brainstem is associated with an increased risk of developing clinical complications. Clinicians may consider this parameter in addition to fractionated stereotactic radiation therapy when well-established dose constraints are not met in this patient population. Additional data are needed to further validate these findings.