Glioblastoma in adults with prior extracranial cancer: a Czech retrospective multicentre study.

Patients with a history of extracranial cancers (EXCA) who develop new intracranial lesions are commonly presumed to harbour brain metastases, yet primary glioblastoma (GBM) can also arise de novo in cancer survivors. The clinical course, molecular features, and treatment outcomes of GBM in this population remain incompletely characterised. We retrospectively analysed adult patients with concurrent prior solid EXCA and supratentorial GBM treated at three Czech neuro-oncology centres between January 2010 and December 2022. Patients with hematologic malignancies or needle-biopsy-only diagnoses were excluded. Demographic, clinical, molecular (IDH, MGMT), surgical (RANO RESECT 2022 extent-of-resection classification), and treatment data were collected and related to progression-free survival (PFS) and overall survival (OS) using Kaplan-Meier estimation, log-rank tests, and Cox regression. Of 1,182 patients operated for GBM, 48 (4.0%) had a documented prior solid EXCA. Median age at EXCA diagnosis was 57.5 years (range 21-82); median age at GBM diagnosis was 65 years (range 46-82). The median interval between diagnoses was 5.7 years (range 0.1-27.3). All 48 GBMs were IDH-wildtype; MGMT promoter status was assessable in 23 cases (17 unmethylated, 6 methylated), of which 22 had follow-up data available for survival analysis. Median PFS was 8.4 months (95% CI 7.6-27.3) and median OS was 10.6 months (95% CI 5.7-16.8). MGMT methylation (mOS 29.3 vs 12.0 months; p = 0.037), higher Karnofsky score, more radical surgical resection, and completion of the Stupp protocol (mOS 19.2 vs 2.5 months for no oncotherapy; p = 0.019) were each significantly associated with longer OS. A new brain lesion in a cancer survivor must not be assumed to be metastatic without histological confirmation. When patients with GBM after prior EXCA are eligible for standard radical surgery and Stupp-protocol oncotherapy, survival outcomes are comparable to those reported for sporadic GBM. Standard treatment protocols are appropriate for this population; a history of extracranial cancer is not in itself an adverse prognostic factor.