Incidence and outcome of pseudoprogression after radiation therapy in glioblastoma patients: a cohort study

Abstract Background Differentiating post-radiation MRI changes from progressive disease (PD) in glioblastoma (GBM) patients represents a major challenge. The clinical problem is two-sided; avoid termination of effective therapy in case of pseudoprogression (PsP) and continuation of ineffective therapy in case of PD. We retrospectively assessed incidence, management, and prognostic impact of PsP and analyzed factors associated with PsP in a GBM patient cohort. Methods Consecutive GBM patients diagnosed in South-Eastern Norway Health Region from 2015 to 2018 who had received RT and follow-up MRI were included. Tumor, patient, and treatment characteristics were analyzed in relationship to re-evaluated MRI examinations at three and six months post-radiation using Response Assessment in Neuro-Oncology criteria. Results A total of 284 patients were included in the study. PsP incidence three and six months post-radiation was 19.4% and 7.0%, respectively. In adjusted analyses, methylated O 6-methylguanine-DNA methyltransferase (MGMT) promoter and absence of neurological deterioration were associated with PsP at both three (p<0.001 and p=0.029, respectively) and six months (p=0.045 and p=0.034, respectively) post-radiation. For patients retrospectively assessed as PD three months post-radiation, there was no survival benefit of treatment change (p=0.838). Conclusion PsP incidence was similar to previous reports. In addition to the previously described correlation of methylated MGMT promoter with PsP, we also found that absence of neurological deterioration significantly correlated with PsP. Continuation of temozolomide courses did not seem to compromise survival for patients with PD at three months post-radiation; therefore, we recommend continuing adjuvant temozolomide courses in case of inconclusive MRI findings.