Abstract
Background: Current target volume delineation protocols for glioblastoma utilise uniform or isotropic expansion around the surgical cavity and residual tumour, without considering specific sites at risk for infiltration. Tumours arising in different neuroanatomical sites may demonstrate distinct patterns of infiltration. This study aims to review the infiltration and progression sites for the occipital lobe glioblastoma to identify sites potentially at risk. Methods: Patients with occipital lobe glioblastoma managed according to the EORTC-NCIC protocol were identified through a prospective database. Based on MRI analysis, a qualitative description of sites of tumour infiltration and subsequent progression was performed. These were categorised into neuroanatomical subsites adjacent to the occipital lobe: level 1 related to the origin gyrus; level 2 related to adjacent gyral subsites; and level 3 related to subsites that involved distant regions. Patients could be classified in more than one level where multifocal involvement was present at diagnosis or progression. Spatial patterns were assessed in relation to three major white matter tracts: inferior longitudinal fasciculus, cingulum, and corpus callosum. Results: A total of 46 patients were analysed. At diagnosis, 20 patients (43.5%) had medial occipital lobe involvement and 26 (56.5%) had lateral involvement. Level 2 and level 3 infiltration were observed in 33 (71.7%) and 27 (58.7%) patients. Progression occurred in 43 patients (93.5%), with involvement at level 1 in 28%, level 2 in 77%, and level 3 in 98%. Lateral tumours demonstrated proportionately higher progression in the trigone (75% vs. 52.6%) and anterior temporal lobe (50% vs. 15.8%, p = 0.026), while medial tumours more frequently involved the splenium (47.3% vs. 16.7%, p = 0.046). Conclusions: Infiltration and progression of occipital lobe glioblastoma may demonstrate distinct neuroanatomical patterns, with spatial distribution corresponding to major white matter tracts.