NCOG-13. OUTCOMES OF CNS WHO GRADE 2 OLIGODENDROGLIOMA IN ADULT PATIENTS ; IMPACT OF ADJUVANT TREATMENT ON OVERALL RESULTS

Abstract

Abstract OBJECTIVE Patients with oligodendroglioma (ODG), isocitrate dehydrogenase (IDH)-mutant, 1p19q codeleted, CNS WHO grade 2 have a median overall survival of longer than 10 years. Patients with ODG who are high-risk by RTOG criteria are offered radiation in combination with procarbazine, lomustine, and vincristine (PCV). The study aims to analyze the patient’s outcomes and assess the efficacy of postoperative treatment. METHODS A total of 138 adult patients who underwent resection for newly diagnosed grade 2 ODG between 1994 and 2021 were enrolled. Sixty-three (45.7%) were observed after gross total resection (GTR) or near total resection (NTR), 5 (0.4%) received adjuvant treatment after GTR or NTR, 37 (26.8%) were observed after subtotal resection (STR) or biopsy, and 33 (24.0%) received adjuvant treatment after STR or biopsy. The study analyzed progression-free survival (PFS), overall survival (OS), and risk variables. RESULTS Out of the 138 patients, 38 (27%) patients received adjuvant treatment, with 30 of them (78.9%) underwent radiotherapy only, 6 (15.8%) underwent radiochemotherapy, and 2 (5.3%) received chemotherapy alone. The median PFS was 6.8 years. Multivariate analysis revealed STR or biopsy (p=0.04), initial MR imaging enhancement (p=0.002), and postoperative observation(p=0.006) were associated with poorer PFS outcomes. The 5-year overall survival rate was 95.5% and the 10-year overall survival was 76.1%. Poor OS prognosis was associated with STR or biopsy (p=0.03), preoperative seizure (p=0.002), and initial MR imaging enhancement (p< 0.001). CONCLUSIONS : GTR and NTR is essential for achieving prolonged PFS and OS in ODG patients. Postoperative treatment is associated with favorable PFS outcomes but does not significantly affect OS. For an accurate diagnosis and appropriate treatment, the utmost care should be taken to avoid underestimating the results of the biopsy.