Evaluating the Impact of Hippocampal Sparing During Whole-Brain Radiation Therapy on Neurocognitive Functions and the Correlations With Hippocampal Dosimetry: A Preliminary Report of a Prospective Observational Study

Abstract

Purpose/Objective(s): Whole brain radiation therapy (WBRT) is the treatment of choice for patients with brain metastases. However, neurocognitive functions (NCF) decline due to impaired hippocampal neurogenesis might occur after WBRT. It is hypothesized that conformal hippocampal sparing during the course of WBRT (HS-WBRT) might provide meaningful NCF preservation. Our study aims to demonstrate the impact of delivering HA-WBRT on NCF changes in patients receiving therapeutic or prophylactic WBRT. Additionally, we attempt to investigate the correlations between hippocampal dosimetric parameters and the above NCF changes or declines Materials/Methods: Forty prospectively enrolled patients were referred for WBRT for PCI or treating oligometastatic brain disease. Before the initiation of HA-WBRT course, all participants must receive baseline neurocognitive assessment, including memory, executive functions and psychomotor speed. The primary endpoint is delayed recall, as determined by the change/decline in either verbal memory (WMS IIIe Word List Learning) or non-verbal memory (WMS III- Visual Reproduction) from baseline assessment to 4 months after the start of HA-WBRT. Hippocampal dosimetric parameters include mean dose received by the hippocampus, the dose delivered to 100% (D100%) of the hippocampus, and V40. Results: Only 3 patients belonged to the clinical setting of PCI; the remaining 37 patients had oligometastatic brain disease, in which the majority metastasized from primary lung cancer. Regarding neurocognitive outcomes, no statistically significant differences were found between various NCF scores obtained at baseline and at post-radiation therapy intervals, in terms of immediate verbal memory and non-verbal memory, except for delayed recall memory on Word List (F Z5.727, p Z0.048). According to the Spearman correlation coefficients, all dosimetric parameters we are interested in fail to be significantly correlated with NCF decline/change after HS-WBRT in the current report. Conclusion: Functional preservation by hippocampal sparing during the courseofWBRTcouldlargelybeachievedinthispreliminarystudy.Ourstudy further suggests that HA-WBRT should be a feasible technique preserving important neurocognitive functions while maintaining intracranial control. Author Disclosure: P. Tsai: None. T. Wu: None. C. Yang: None. C. Tseng: None. P. Pai: None. D. Tsan: None. S. Lin: None.