title: Low incidence of melanoma brain metastasis in the hippocampus.
abstract: OBJECTIVE
  ANZMTG 01.07 WBRTMel is a phase 3 randomized trial to address the role of whole brain radiation therapy (WBRT) after local treatment of 1-3 melanoma brain metastases. Modern radiation therapy technologies can now conformally spare the hippocampus during WBRT and therefore potentially reduce the risk of neurocognitive deficit. The aims of this study were to report the prevalence of melanoma metastases within the hippocampal sparing region and to identify variables that correlate with the presence of metastases within the hippocampal sparing region.
  
  
  METHODS
  The pre-local treatment MRI scans of 77 eligible WBRTMel patients were used to contour the individual metastasis and the hippocampus. The volume, location and closest distance of each metastasis to the hippocampus were recorded. Binary logistic regression was performed to assess the influence of factors on the location of a metastasis within 5mm of the hippocampus.
  
  
  RESULTS
  The median age was 61 and 66% were male. The distribution of the 115 metastases was frontal (50, 43.5%), parietal (23, 20.0%), temporal (13, 11.2%), occipital (18, 15.7%), cerebellum (10, 8.6%) and pineal gland (1, 1.0%). The median aggregate volume of the metastasis was 3516mm(3). None of the metastases were within the hippocampus. Four patients (5.2%) had metastases within 5mm of the hippocampus. The median distance from metastasis to the nearest hippocampus was 37.2mm. Only the total volume of metastases was a significant predictor for the risk of a metastasis within the hippocampal sparing region (OR 1.071, 95% CI: 1.003-1.144, p=0.040).
  
  
  CONCLUSIONS
  This study confirmed a low incidence of melanoma metastasis in the hippocampal sparing region at diagnosis. Given the lack of randomized data on the safety and benefit of hippocampal sparing WBRT, the current WBRTMel trial provides the opportunity to explore the feasibility of this technique.
authors.affiliation: Melanoma Institute Australia, Poche Centre, North Sydney, Australia; Department of Medicine, Central Clinical School, The University of Sydney, Australia; Department of Radiation Oncology, Royal Prince Alfred Hospital, Sydney, Australia; Australia and New Zealand Melanoma Trials Group, North Sydney, Australia. Electronic address: angela.hong@melanoma.org.au.
authors.forename: Angela M
authors.initials: AM
authors.lastname: Hong
authors.affiliation: Regenerative Neuroscience Group, Brain & Mind Research Institute, The University of Sydney, Australia.
authors.forename: Chao
authors.initials: C
authors.lastname: Suo
authors.affiliation: Regenerative Neuroscience Group, Brain & Mind Research Institute, The University of Sydney, Australia.
authors.forename: Michael
authors.initials: M
authors.lastname: Valenzuela
authors.affiliation: Melanoma Institute Australia, Poche Centre, North Sydney, Australia; Department of Medicine, Central Clinical School, The University of Sydney, Australia.
authors.forename: Lauren E
authors.initials: LE
authors.lastname: Haydu
authors.affiliation: Australia and New Zealand Melanoma Trials Group, North Sydney, Australia; Department of Medical Oncology, The Norwegian Radium Hospital, Oslo, Norway.
authors.forename: Kari D
authors.initials: KD
authors.lastname: Jacobsen
authors.affiliation: Australia and New Zealand Melanoma Trials Group, North Sydney, Australia; Department of Radiology and Nuclear Medicine, The Norwegian Radium Hospital, Oslo, Norway.
authors.forename: Claudius H
authors.initials: CH
authors.lastname: Reisse
authors.affiliation: Melanoma Institute Australia, Poche Centre, North Sydney, Australia; Australia and New Zealand Melanoma Trials Group, North Sydney, Australia; Genesis Cancer Care, Mater Hospital, North Sydney, Australia.
authors.forename: Gerald
authors.initials: G
authors.lastname: Fogarty
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001932:Brain Neoplasms / Q000532:radiotherapy* / Q000556:secondary*; D016371:Cranial Irradiation / Q000379:methods; D005260:Female; D006624:Hippocampus / Q000473:pathology* / Q000528:radiation effects*; D006801:Humans; D015994:Incidence; D008279:Magnetic Resonance Imaging; D008297:Male; D008545:Melanoma / Q000473:pathology / Q000532:radiotherapy* / Q000556:secondary*; D008875:Middle Aged; D012306:Risk
keywords: Brain metastasis; Hippocampal sparing; Melanoma; Radiotherapy; Whole brain