Efficacy of Hippocampal Avoidance Whole Brain Radiotherapy to Preserve the Cognitive Functions among Brain Metastasis Patients: Systematic Review and Meta-analysis.

This systematic review and meta-analysis aims to gather credible sources of comprehensive information on the efficacy and radiation dose (maximum and minimum) to the hippocampus and contouring area to prevent cognitive dysfunction by hippocampal avoidance whole brain radiation therapy (HA-WBRT). This comprehensive review was conducted in compliance with PRISMA guidelines. The systematic literature search was performed across four databases including pubmed®, Scopus®, Cochrane Library®, and clinicaltrial.gov.in from inception until December 31, 2023. A total of nine eligible studies were selected encompassing a total of 680 patients with brain metastases who underwent radiation therapy. Notably, radiation exposure to the hippocampal area (3 to 7 mm margin) was avoided during whole-brain radiation therapy (WBRT). The maximum dose delivered to the hippocampus varied between 12.61 Gy and 17 Gy in different studies with minimum doses varying from 5.38 Gy to 10 Gy. HA-WBRT significantly preserves delayed recall compared to WBRT (p = <0.001, P = <0.001, <0.001 and P = 0.048), with an effect size (SMD: -0.57, 95% CI: -1.27, 0.12, P = 0.59, I2 = 0%) favoring HA-WBRT. However, the changes in psychomotor speed, visuospatial abilities, executive function, verbal fluency, and so on were not statistically significant between HA-WBRT and WBRT groups. This review underscores the significant positive impact of HA-WBRT in preventing radiation-induced neurocognitive dysfunction in brain metastatic patients, particularly in delayed recall. However, comprehensive cognitive preservation necessitates additional interventions alongside HA-WBRT.