Hippocampal Avoidance Whole Brain Radiation Therapy is Associated with Preservation of Hippocampal Volume at Six Months: A Case Series

Background: WBRTMel is a Phase 3 randomised trial comparing immediate whole brain radiation therapy (WBRT) with or without hippocampal avoidance (HA) with observation after local treatment of 1-3 melanoma brain metastasis. We examined a series of patients from this trial to determine effect of radiation therapy on the whole brain and hippocampal volume.

Methods: Patients on the WBRTMel trial without any intracranial failure at 6 months after randomization were included. Whole brain and hippocampal volumes at baseline and 6 months were contoured by investigators blinded to the treatment arm or the timing of scan.

Results: Twenty patients (7 observations, 9 non HA-WBRT and 4 HA-WBRT) with the median age of 62 years were included. There was no significant change in the mean whole brain volume from baseline to 6 months (1458.7 cm3 to 1444.3 cm3, -0.78%) in the WBRT group or in the observation group (1569.0 cm3 to 1572.5 cm3, 0.74%). There was evidence that change in the hippocampal volume from baseline to 6 months in the WBRT group (4.65 cm3 to 4.36 cm3, 5.36%) may be larger than in the observation group (4.24 cm3 to 4.24 cm3, 0%). Also, HA-WBRT tended to preserve the hippocampal volume at 6 months (mean change 0.16%) when compared with non HA-WBRT (-7.1%).

Conclusions: Preliminary data suggests non HA-WBRT may produce a selective atrophy of the hippocampus volume within 6 months. HA-WBRT can possibly minimise this effect. The full WBRTMel trial will be able to define this effect of RT on the hippocampal volume and correlate any change with neurocognitive function and quality of life data


Angela M Hong, Harry Hallock, Michael Valenzuela, Serigne Lo, Elizabeth Paton, Diana Ng, Haryana M Dhillon, Kari D Jacobsen, Claudius H Reisse and Gerald B Fogarty

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