RETROSPECTIVE ANALYSIS OF INITIAL TREATMENT OUTCOMES IN OLIGODENDROGLIOMAS

Introduction: The histological classification of Central Nervous System (CNS) tumors has, since 1926, guided clinical decisions in adjuvant treatments. In 2016, molecular testing was integrated to the new WHO classification better correlating to prognosis and clinical outcomes than the prior classification. Clinical trials have established standard adjuvant treatment options over time. These include observation, radiation therapy (RT), and chemotherapy. For high-risk patients, concurrent chemoradiotherapy (CRT) or sequential RT followed by Temozolomide (TMZ) or Procarbzine, Lomustine and Vincristine (PCV) have been used. Objectives: Review clinical, epidemiological factors and outcomes related to the initial treatment of oligodendrogliomas in patients from a single Brazilian Oncology Center. Methods: Using Recruit we stratified patients with either oligodendroglioma histological diagnosis or molecular 1p/19q codeletion or both, from 1994 until June 2019. Patients with mixed oligoastrocytoma histology and 1p/19q non-codeleted gliomas were excluded. Descriptive analysis of frequencies and central tendency measures were performed. Overall survival (OS) and progression free survival (PFS) were calculated by Kaplan-Meier analysis. Results: Of 51 patients reviewed, 52,9% were female and seizure was the initial symptom in 53,7%. These tumors were diagnosed by Magnetic Resonance Imaging (MRI) in 82,4% of patients and the majority of them were localized in the frontal lobe. Grade 3 tumors were related to an increased risk of progression, when compared to Grade 2, with a median PFS: 17.2 × 81.4 months, respectively (HR PFS 3.39; p = 0.01). Partial resection was associated to an increased risk of death when compared to Subtotal and Gross-total resection (HR OS 12.3; p = 0.03). Adjuvant treatment were as follows: observation in 36,7%, RT in 14,3%, TMZ in 10,2%, sequential TMZ following RT in 24,5% and CRT in 14,3%. TMZ was the main chemotherapy regimen, except for 2 patients. In Grade 2 tumors, the 11 patients who received TMZ were progression free at the time of last follow-up. The main related adverse event was Grade 1-2 nausea (70%). Grade 3 anemia occurred in one patient who required blood transfusion. Conclusion: Besides having a small number of cases, our survival data are similar to that revised in literature and our study suggests that TMZ has similar impact on survival to PCV, considered actual standard adjuvant chemotherapy.