Survival patterns of oligoastrocytoma patients: A surveillance, epidemiology and end results (SEER) based analysis

The 2016 update to the World Health Organization (WHO) states that oligoastrocytoma (OA) should be classified as either oligodendroglioma or astrocytoma based on molecular biomarkers. We examined the survival patterns of patients diagnosed with OA in the Surveillance, Epidemiology and End Results (SEER) registry in the context of this revised scheme. We used data from the SEER database (1999–2010) to identify patients diagnosed with WHO grade II astrocytoma (A2, n = 4113), WHO grade II oligodendroglioma (O2, n = 2378), and oligoastrocytoma (OA, n = 1505). Survival comparison was performed using Kaplan-Meier analysis and multivariate Cox proportional hazards analysis. Similar to O2 patients, gross total resection (GTR) was not associated with improved survival in OA patients. In contrast, GTR is associated with improved survival in A2 patients. For OA patients who did not undergo surgery or radiation therapy (RT), those with tumors < 5 cm in maximal diameter exhibited survival patterns similar to O2 patients, while those with tumors ≥ 5 cm exhibited survival patterns similar to A2 patients. Distinct survival patterns were observed in SEER OA patients with tumors < or ≥ 5 cm in maximal diameter.