Spatial Transcriptomics Characterisation of Radionecrotic Changes in Glioblastoma Patients

Background: IDH-wildtype Glioblastoma (GB) is the most prevalent primary CNS tumour in adults. The standard treatment involves radiotherapy, which can cause radionecrotic changes. Progressive GB and radionecrotic changes can be challenging to differentiate, as they present with similar symptoms and appear alike on MRI. Histopathological examination remains the gold standard of diagnostics. To this date, little is known about the biological mechanisms underlying radionecrotic changes. Methods: The cohort comprised ten samples from nine patients diagnosed with GB, who underwent first-line standard treatment including surgery, radio- and chemotherapy with temozolomide. Subsequent radiological examination identified tumour progression in all patients, necessitating a second surgery. Based on histopathological examination of the material collected from the second surgery, four patients were diagnosed with tumour recurrence, four manifested with radionecrotic changes, and one patient demonstrated both. The spatial single cell transcriptomics profiling of the samples was conducted using the Xenium platform. Results: We generated a comprehensive spatial single cell transcriptomics atlas of progressive GB and brain tissue with radionecrotic changes. Tumour cells were detected in samples from both groups. Progressive GB samples contained OPC/NPC-like and proliferating tumour cells with high EGFR expression. In radionecrotic samples, tumour cells exhibited lower EGFR expression even in the presence of gene amplification and did not show proliferation markers. Border-associated macrophages infiltrated the tissue and might have promoted gliosis in radionecrotic samples. Conclusions: This study delineates a complex spatial architecture of brain tissue with post-treatment changes and its discrepancies from progressive GB, facilitating future research into novel treatment strategies.