Hippocampal Dosimetry and Neurocognitive Function in Patients Undergoing Stereotactic Radiosurgery for Brain Metastases

Abstract

Abstract AIMS To measure neurocognitive function (NCF) and correlate with hippocampus dose in patients undergoing stereotactic radiosurgery (SRS) for 1-3 brain metastases. METHOD We conducted a prospective observational study measuring NCF before and after SRS in patients with 1-3 brain metastases and correlated changes with hippocampal dosimetry Patients underwent NCF testing at baseline, 1 month, 3 months and 6 months post SRS and quality of life was measured at each time point. NCF tests included Hopkin’s Verbal learning test, controlled oral word association test and trail making tests. Hippocampus was outlined in line with RTOG guidance and dose was collected from the treatment planning system. RESULTS 36 patients were recruited. Mean age was 64 years, median WHO performance status 1 (range 0-2). At baseline, 65% of patients displayed NCF impairment in at least 1 NCF domain and 33% didn’t exhibit any neurological symptoms. Asymptomatic patients has underlying diagnosis of non-small cell lung cancer or melanoma. NCF impairment was evident at 1, 3 and 6 months for 50%, 66% and 40% patients respectively. Decline at 1 month was associated with higher median dose to 0.1cc of hippocampus (5 Gy vs 2.35 Gy). Association with hippocampal dose and NCF impairment at 3 and 6 months was not observed. CONCLUSION A significant proportion of patients exhibited impaired NCF at baseline with greatest NCF decline seen at 1 months and subsequent recovery of NCF evident at 6 months. Dose to hippocampus 0.1cc may be associated with acute NCF toxicity. Main limitations of this study was small number of patients.