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Purpose: Glioblastomas (GBM) are the most common malignant primary brain tumors in adults and have a dismal prognosis. Patients frequently suffer from local tumor recurrences, with limited therapeutic options. Re-irradiation represents a possible intervention, but given the recent 5th edition of the World Health Organization classification of central nervous system tumors, studies in isocitrate dehydrogenase wild type (IDH-wt) cohorts undergoing a second course of radiotherapy remain limited. Herein, we sought to describe our institutional experience and outcomes after GBM IDH-wt re-irradiation. Materials and Methods: GBM patients with confirmed IDH-wt status undergoing re-irradiation were included in this single-center, retrospective analysis. Results: A total of 88 patients were analyzed. The median clinical and radiographic follow-up periods were 4.6 months and 4.4 months, respectively. Most patients had a Karnofsky performance status of at least 80% (n = 57). The median biologically effective dose and 2 Gy equivalent dose (EQD2) for re-irradiations, assuming an α/ß ratio of 10 Gy for GBM, were 51.4 and 42.8 Gy, respectively. In total, 71 deaths were recorded. The median overall survival (OS) was 8.0 months. Multivariable Cox regression of OS revealed a positive influence of gross total resection vs. biopsy or no resection (hazard ratio: 0.43, p = 0.02). The median progression-free survival (PFS) was 5.9 months. The multivariable Cox regression for PFS did not detect any significant factors. No clear evidence of radiation necrosis was recorded during the available follow-up. However, only a minority (n = 4) of patients underwent surgery after re-irradiation, none showing histopathological proof of radiation necrosis. Conclusion: The prognosis for recurrent IDH-wt GBM after re-irradiation is poor. Patients who are amenable and able to undergo re-resection may have a favorable OS. A second course of radiotherapy with a moderate cumulative EQD2 and small- to medium-sized planning target volumes appeared safe regarding the occurrence of radiation necrosis.
RESUMEN
Background: Oligodendrogliomas (ODG) are rare, diffusely infiltrating brain tumors, defined by their 1p/19q-codeletion and isocitrate dehydrogenase (IDH) mutation. Herein, we analyze the influence of various tumor and patient characteristics on progression-free survival (PFS) and overall survival (OS) in a homogeneous patient cohort. Material and methods: Patients treated for a 1p/19q-codeleted and IDH-mutant ODG were evaluated. The patient and tumor characteristics were analyzed for their influence on PFS and OS. Results: One-hundred-fourteen patients met the inclusion criteria. The median clinical and radiographic follow-up periods were 68.6 and 69.8 months. The median PFS and OS were 66.9 and 236.0 months, respectively. The 2-, 4- and 6-year PFS rates were 89.5%, 76.3%, and 46.0%. The 2-, 4- and 6-year OS rates were 99.0%, 97.9%, and 96.2%. For WHO grade 2 ODG, extent of resection (p = 0.01, hazard ratio (HR) 0.01; p = 0.02, HR 0.02), radiotherapy (p = 0.01, HR < 0.01) and chemotherapy (p = 0.01, HR < 0.01) were associated with a prolonged PFS. For WHO grade 3 ODG, only a combined radiochemotherapy (RCT) lowered the risk of progression in the multivariable analysis (p = 0.02, HR 0.09). Most RCT patients received temozolomide (TMZ) instead of procarbazine, lomustine, and vincristine. Conclusion: Whereas previous studies often comprise tumors with IDH wild type status and without 1p/19q-codeletion, this homogeneous ODG cohort, as defined by the current WHO classification, demonstrated PFS benefits for various therapies, especially concerning RCT. While this is generally in accordance with comparable studies, more prospective work on homogeneous patient cohorts is required to refine treatment guidelines and to determine the role of TMZ in ODG.
