# Assessment of Patterns of Infiltration and Relapse of Patients with Glioblastoma of the Occipital Lobe

## TL;DR

This study finds that occipital lobe glioblastoma often spreads to distant brain regions connected by white matter pathways, which could improve radiotherapy planning.

## Contribution

The study identifies distinct infiltration and relapse patterns of occipital lobe glioblastoma linked to major white matter tracts.

## Key findings

- Tumour infiltration extends beyond the primary site into anatomically connected brain regions.
- Relapse frequently occurs at distant neuroanatomical sites rather than the original tumour location.
- Lateral and medial tumours show different progression patterns in specific brain regions.

## Abstract

What are the main findings?
Occipital lobe glioblastoma frequently demonstrates tumour infiltration beyond the primary gyral subsite into anatomically connected brain regions.Progression commonly occurs at distant neuroanatomical sites rather than remaining confined to the original tumour location.

Occipital lobe glioblastoma frequently demonstrates tumour infiltration beyond the primary gyral subsite into anatomically connected brain regions.

Progression commonly occurs at distant neuroanatomical sites rather than remaining confined to the original tumour location.

What are the implications of the main findings?
Patterns of spread appear consistent with major white matter pathways connecting occipital and distant brain regions.Recognition of these patterns may help inform future radiotherapy target delineation.

Patterns of spread appear consistent with major white matter pathways connecting occipital and distant brain regions.

Recognition of these patterns may help inform future radiotherapy target delineation.

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.