2619 - Change in Cognitive Function in Patients with Brain Metastasis Treated with Stereotactic Radiosurgery Quantified by Hippocampal Dose
Presenter(s)
P. Kimmel1, H. Moulding2, X. Song3, J. A. Jones4, T. Xue4, and W. H. Smith2; 1Temple/St. Luke's School of Medicine, Bethlehem, PA, 2St. Luke's University Health Network, Bethlehem, PA, 3St Luke's University Health Network, Easton, PA, United States, 4St. Luke's University Health Network, Bethlehem, PA, United States
Purpose/Objective(s): Stereotactic Radiosurgery (SRS) is a form of precisely delivered radiation therapy that can be used to target brain metastasis. SRS offers several therapeutic advantages over whole brain radiation therapy (WBRT) including more targeted delivery of the radiation to metastases with sparing of critical structures like the hippocampus. This allows patients undergoing SRS to better maintain cognitive function as compared to those receiving WBRT. Nonetheless, the role of hippocampal dose in SRS remains unclear. We sought to investigate the effect of hippocampal dose on cognitive functioning in patients undergoing SRS for brain metastases.
Materials/Methods: We retrospectively identified patients who underwent SRS for brain metastases at our institution between 01/01/2017 and 12/06/2021. During this time pre-treatment and post-treatment Montreal Cognitive Assessment (MOCA) scores were routinely obtained during clinic visits. Treatment data were abstracted from chart review and max hippocampus dose was determined from SRS plans. For patient’s undergoing multiple treatment courses, cumulative doses from plan summations were used. Patients were dichotomized into higher and lower dose groups using a cut off of 0.7 Gy. This cut off was chosen based on the distribution of doses observed. Wilcoxon rank sum analysis was performed to compare change in MOCA score between high and low dose groups and linear analysis was used to compare increasing hippocampal dose with change in MOCA.
Results: Fifty-one instances of treatment were recorded. The most common primary tumor site was non-small cell lung cancer (52.9%), and the most frequent area of the brain treated was the frontal lobe (31.4%). 44 treatments were categorized as low hippocampus dose and 7 were categorized as high dose. Compared to pretreatment MOCA scores, post-treatment MOCA decreased on average by 0.76 points across our entire cohort (p = 0.005). Comparing the high-dose vs low-dose subgroups, we saw a greater decrease in MOCA score among the high group, though this difference was not statistically significant (p = 0.1781). When represented as a continuous variable, linear analysis did not demonstrate maximum hippocampal dose to be associated with MOCA score change (p = 0.32).
Conclusion: Among our cohort we observed a decrease in MOCA score, reflective of worsened cognition over time and following SRS. However, we did not observe a significant correlation between high hippocampus dose and decrease in MOCA score, suggesting an effect from other factors, such tumor burden, progression of intracranial disease, and effect of other treatments (e.g. systemic therapy). Statistical power was likely limited by a small number of patients receiving high hippocampus dose on SRS.