P06.03 Anaplastic oligodendroglioma and oligoastrocytoma without 1p-19q co-deletion: a mono-institutional retrospective study

AbstractAllelic losses of chromosomes 1p and 19q in patients with anaplastic oligodendroglioma(AOD) and oligoastrocytoma(AOA) represent a strong prognostic factor and a powerful predictor of survival. These subset of patients benefit from the addition of chemotherapy(CT) to radiotherapy(RT), with a significant improvement of overall survival (OS) and progression-free survival (PFS). In patients without 1p19q co-deletion, there are no standard-of-care and conflicting opinions impose to review the possible therapeutic approach. A total of 214 patients with histological proven of AOD and AOA treated in our Institution over the last 10 years were evaluated. Eighty patients were eligible for loss-of-heterozigosity (LOH) evaluation. The absence of 1p19q co-deletion was confirmed in 33 patients. Clinical and genetic data, treatments and survival assessment were described and discussed. In non co-deleted group, m-OS and m-PFS were respectively 38,4 months (95% CI 21,99-59,77) (P=0,018) and 16 months (95% CI 13,0-20,0). On the other hand, m-OS of the whole group was 59.7 months. Concerning treatments, therapeutic approach has been variable with a higher percentage in RT and concomitant temozolomide in the past two years. In 6% of patients CT was considered as first-line treatment after surgery. Data confirmed the prognostic role of LOH, with the most advantages for patients with co-deletion. Regarding therapeutic approaches, results show a quite aggressive attitude in our clinical practice. The choice between RT or CT as first line treatment after surgery do not seem to influence the prognosis.