Retrospective study of surgical characteristics and postoperative outcomes of patients with molecularly defined oligodendroglioma

Oligodendroglioma, an adult diffuse glioma now defined by molecular criteria, is typically managed first surgically. A retrospective study at Johns Hopkins University School of Medicine (Baltimore MD) analyzed surgical characteristics and postoperative outcomes among patients with surgically managed 1p/19q co-deleted, IDH-mutated oligodendroglioma. The study included 277 patients (207 grade 2, 70 grade 3); most presented with seizures (64.8%), non-contrast enhancing lesions (60.1%), and frontal lobe tumors (63.7%). Subtotal resection (STR; 46.2%) and gross total resection (GTR; 39.9%) were more common than biopsy (14.9%). Awake procedures were performed in 14.5%. New permanent neurologic deficits occurred in 9.4%. The median follow-up was 57 months (IQR 20-107). Individuals undergoing GTR or STR had longer median progression-free survival (PFS) than patient who underwent biopsy (76 versus 44 months; p=0.007). In multivariable analysis, GTR, but not STR, was an independent predictor of improved PFS compared to biopsy after adjusting for demographics, grade, and adjuvant treatment (p=0.026). The PFS benefit of GTR over biopsy was maintained in subgroup analyses of grade 2 tumors (p=0.032) but not grade 3 tumors (p=0.549). The authors conclude that GTR was associated with prolonged PFS compared to biopsy without an observed increase in postoperative neurological deficits.