Patterns of management and outcomes of unifocal versus multifocal glioblastoma

Background: Glioblastoma (GBM) presents as a solitary lesion (unifocal), or as multiple discrete lesions (multifocal). Multifocal GBM may have a worse prognosis as compared to unifocal GBM, but existing data are limited to small institutional series. The purpose of the present study was to evaluate demographic and clinical characteristics of patients with unifocal versus multifocal GBM to highlight demographic differences and clinical outcomes for two groups of patients. Methods: The National Cancer Database (NCDB) was queried (2004–2016) for patients newly diagnosed with either unifocal or multifocal GBM. Statistics included Kaplan-Meier overall survival (OS) analysis, along with Cox proportional hazards modeling. Results: Of 45,268 total patients, 37,483 (82.8%) had unifocal GBM and 7,785 (17.2%) had multifocal GBM. Patients with unifocal GBM more frequently received gross total resection (GTR) (41.2% versus 25.8%, p < 0.001) and conventionally fractionated radiation therapy (RT) (48.2% versus 42.7%, p < 0.001). Patients with multifocal GBM had a higher rate of surgery with biopsy only (34.0% compared to 24.1%, p < 0.001). Median OS was 12.8 months versus 8.3 months (p < 0.001) for patients with unifocal GBM or multifocal GBM, respectively. On multivariate analysis, factors associated with improved OS included unifocal disease, MGMT methylation, RT use, and chemotherapy use. Conclusions: This is the largest study to date describing outcomes for patients with multifocal GBM, and it shows that multifocal GBM is associated with a decreased use both of GTR and conventionally fractionated RT, as well as worse median OS. Further research is needed to improve clinical outcomes for patients with multifocal GBM.