Pediatric oligodendrogliomas are infrequently occurring brain tumors and frequently thought of as benign. The literature examining treatment and outcome in this select population is sparse. A retrospective analysis of pediatric oligodendrogliomas treated at MD Anderson Cancer Center between 1973 and 1992 was performed. Oligodendrogliomas were histologically graded according to the method of Smith. Survival data were estimated with Kaplan-Meier curves. Mean follow-up was 39.7 months. Nineteen children had histologically verified oligodendrogliomas and mixed oligodendroglioma/astrocytoma (M:F = 11:8; age range 1–18 years, mean = 13.1). Presenting symptoms included seizures (n = 10), headache (n = 3), visual field defects (n = 2), weakness (n = 2), cranial nerve palsy (n = 1) and decreased school performance (n = 1). All patients underwent craniotomy: 13 subtotal resections, 5 gross total resections and 1 biopsy. Twelve children had adjuvant therapy including radiation (n = 12), chemotherapy (n = 5) or both (n = 5). The 5-year survival was 65%. Seizure frequency was reduced in 30%. Children with oligodendrogliomas do not have a benign course, but younger children (<12 years) have a better prognosis. Histologic classification correlates with survival. Completeness of resection was not found to be a factor relating to survival. No conclusions can be drawn concerning adjuvant therapy because of selection bias.

Allelic loss of chromosome 1p is frequently observed in oligodendroglioma. We screened 177 oligodendroglial tumors for 1p deletions and found 6 tumors with localized 1p36 deletions. Several apoptosis regulation genes have been mapped to this region, including Tumor Protein 73 (p73), DNA Fragmentation Factor subunits alpha (DFFA) and beta (DFFB), and Tumor Necrosis Factor Receptor Superfamily Members 9 and 25 (TNFRSF9, TNFRSF25). We compared expression levels of these 5 genes in pairs of 1p-loss and 1p-intact tumors using quantitative reverse-transcriptase PCR (QRTPCR) to test if 1p deletions had an effect on expression. Only the DFFB gene demonstrated decreased expression in all tumor pairs tested. Mutational analysis did not reveal DFFB mutations in 12 tested samples. However, it is possible that DFFB haploinsufficiency from 1p allelic loss is a contributing factor in oligodendroglioma development.

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Pseudoprogression (psPD) refers to an increase in size or appearance of new areas of MRI contrast enhancement soon after completing chemoradiation, timely diagnosis of which has been a challenge. Given that tissue sampling of the MRI changes would be expected to accurately distinguish psPD from true progression when MRI changes are first seen, we examined the utility of surgery in diagnosing psPD and influencing patient outcome. We retrospectively reviewed data from adults with GBM who had MRI changes suggestive of progression within 3 months of chemoRT; of these, 34 underwent surgical resection. Three subsets-tumor, psPD or mixed-were identified based on histology and immunohistochemistry in the surgical group and by imaging characteristics in the nonsurgical group. A cohort of patients with stable disease post-chemoRT served as control. PFS and OS were determined using the Kaplan-Meier method and log rank analysis. Concordance for psPD between radiological interpretation and subsequent histological diagnosis was seen in only 32 % of cases (11/34) 95 %CI 19-49 %. A large proportion of patients had a histologically "mixed" pattern with tumor and treatment effect. No significant differences in PFS or OS were seen among the three subtypes. Surgical sampling and histologic review of MRI changes after chemoRT may not serve as a gold standard to distinguish psPD from true progression in GBM patients. Refinement of the histological criteria, careful intraoperative selection of regions of interest and advanced imaging modalities are needed for early differentiation of PsPD from progression to guide clinical management.

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