Oligodendroglioma with Sarcomatous Transformation: Case Report and Literature Review

Oligodendrogliomas are infiltrative tumors of the central nervous systemconsidered to be morphologically stable and to offer a better prognosis. Here, we describe the case of a 36- year-old man with an initial diagnosis of oligodendroglioma, World Health Organization (WHO) grade II, who presented transformation to a sarcomatous form, while maintaining the oligodendroglial component as well as the genetic characteristics of the initial tumor without having undergone any complementary treatments previously. Despite the favorable genetic characteristics, the tumor presented poor response to complementary treatments, and rapid progression, including spinal metastasis.

Genetic landscape of extreme responders with anaplastic oligodendroglioma.

BACKGROUND: The NRG Oncology RTOG 9402 trial showed significant survival benefit in patients with 1p/19q co-deleted anaplastic oligodendrogliomas (AO) who received both radiation (RT) and chemotherapy (PCV regimen) versus RT alone. Substantial separation of the survival curves was only seen after 7.3 years. We aimed to determine whether there are specific genetic alterations that distinguish co-deleted AO patients who benefit from the addition of PCV from those who do not. METHODS: We performed whole exome sequencing on matched tumor and normal DNA from all available short-term (STS) and long-term survivors (LTS) who received RT+PCV. hTERT status and rs55705857 genotypes (G-allele) were analyzed in both cohorts. RESULTS: Six STS (survival of <7.3y) and 7 LTS (survival of ≥7.3y and no progression) had sufficient material for analysis. There was no significant difference between the groups regarding age, performance status and extent of resection. On average, STS had 7 and LTS 4 mutations. Most common mutations in STS vs. LTS were: IDH1 (67 vs. 86%), CIC (50 vs. 71%) and FUBP1 (17 vs. 71%). The hTERT promoter was mutated in 83% STS and 86% LTS. Genotyping of rs55705857 showed a higher prevalence of G allele carriers in LTS than STS (43 vs. 17%). CONCLUSIONS: These findings confirm that IDH, CIC, FUBP1 mutations and rs55705857 genotype are common in AO. No distinct genetic signature was identified to differentiate STS and LTS.

New treatment paradigm for patients with anaplastic oligodendroglial tumors.

Oligodendrogliomas are uncommon tumors in neurooncology that represent about 5% of primary brain malignancies. Their high sensitivity to radiotherapy and chemotherapy was observed a long time ago. Nonetheless, the evidence-based proof of the significantly longer survival in patients with oligodendrogliomas treated with combined chemotherapy and radiotherapy in comparison to radiotherapy-alone did not exist. The long-term follow-up of two landmark phase III clinical trials: RTOG 9402 and EORTC 26951, recently demonstrated favorable effects of combined radiotherapy and chemotherapy (procarbazine, lomustine and vincristine) in patients with anaplastic oligodendrogliomas and anaplastic oligoastrocytomas carrying the chromosomal mutation of co-deletion of 1p/19q. There is also an increasing role of other molecular biomarkers, such as mutations in the metabolic enzyme isocitrate dehydrogenase 1/2, O6-methylguanine DNA methyltransferase gene promoter methylation, or glioma genome cytosine-phosphate-guanine islands methylator phenotype. The analysis of molecular genetics in oligodendrogliomas is now recommended as an important part of the management of these tumors and together with the novel chemotherapeutic regimens means a paradigm shift in current clinical practice in neurooncology.