Hippocampal-sparing radiotherapy and neurocognitive impairment: A systematic literature review

Introduction: Whole-brain radiation therapy (WBRT) is an effective therapeutic modality in patients with brain metastases. However, nearly 90% of patients undergoing WBRT suffer from a neurocognitive function (NCF) impairment at diagnosis, and up to two-thirds will experience a further decline within 2-6 months after WBRT. Focal-dose reduction on bilateral hippocampus is thought to improve NCF preservation. The aim was to present a systematic review of clinical results on NCF after hippocampal-sparing (HS) WBRT. Materials and Methods: A systematic review of published literature was performed on PubMed and the Cochrane Library. Only prospective clinical trials reporting NCF outcome in patients treated with HS-WBRT have been analyzed. Results: A total of 165 patients from three studies were included. These studies are characterized by small sample size and different methods in terms of WBRT technique but with similar planning analysis and NCF assessment tests. No significant changes in NCF (i.e., verbal and nonverbal learning memory, executive functions, and psychomotor speed) between baseline and 4-month follow-up after RT and only a mean relative decline in delayed recall at 4 months (7% compared to 30% of historical control) were observed. Conclusions: Considering preliminary results on NCF preservation, further studies seem justified in patients undergoing brain irradiation for brain metastases or referred for prophylactic cranial irradiation to evaluate long-term effects on NCF and quality of life.