Background
Glioblastoma (GBM) is the most aggressive and malignant tumor of the central nervous system, characterized by poor prognosis despite standard treatments such as maximal resection, temozolomide (TMZ) chemotherapy, and radiotherapy. Recent studies, including the phase II REGOMA trial, have highlighted regorafenib (REGO) as a promising second-line treatment. This study integrates two key investigations: (1) the molecular mechanisms behind REGO sensitivity in recurrent GBM (rGBM) and (2) the correlation between ex vivo drug sensitivity testing on patient-derived organoids and clinical outcomes after second-line chemotherapy.
Methods
Patient-derived 3D glioblastoma organoids (GBM-EXPs) were developed from 26 samples (18 patients), encompassing primary, recurrent, and peripheral tumors. The organoids were treated with TMZ or REGO, and drug response was assessed using NAD(P)H Fluorescence Lifetime Imaging (FLIM). Whole-exome and transcriptome analyses were conducted on selected samples. In addition, clinical outcomes from a prospective study of 16 patients were correlated with the ex vivo drug response assays.
Results
Out of the 26 samples, 35% were sensitive to TMZ, while 77% were sensitive to REGO. REGO-sensitive tumors exhibited distinct mutational and transcriptional profiles, including alterations in OR13C5 and MLLT3, and changes in pathways such as Rho GTPase and NOTCH signaling. In the clinical study, rGBM-EXPs that were sensitive to REGO showed significantly longer progression-free survival (PFS2) compared to those not sensitive to REGO (7.5 months vs. 3.6 months; p=0.04). The ex vivo testing influenced treatment decisions, resulting in longer median PFS2 (7.4 months vs. 4.6 months; p=0.08) and overall survival (OS2) (not reached vs. 6.3 months; p=0.03).
Conclusions
This study demonstrates that REGO is more effective than TMZ for treating recurrent GBM, with sensitivity strongly associated with molecular profiles. The use of ex vivo drug response testing with NADH-FLIM shows promise in predicting the efficacy of second-line therapies and guiding personalized treatment strategies. These findings underscore the potential of functional precision medicine in enhancing outcomes for GBM patients.