Surgical characteristics and postoperative outcomes in a retrospective cohort study of patients with molecularly defined oligodendroglioma.

PURPOSE: Oligodendroglioma, an adult diffuse glioma now defined by molecular criteria, is typically managed first surgically. This retrospective cohort study correlates surgical characteristics with postoperative outcomes in purely molecularly defined oligodendroglioma.

METHODS

Adults with surgically managed 1p/19q co-deleted, IDH-mutated oligodendroglioma were identified. Medical records were reviewed for demographics, radiologic features, treatments, and postoperative outcomes.

RESULTS

Two hundred seventy-seven patients (207 grade 2, 70 grade 3) were included; most presented with seizures (173/267, 64.8%), non-contrast enhancing lesions (128/213, 60.1%), and frontal lobe tumors (170/267, 63.7%). Subtotal resection (STR, 115/249, 46.2%) and gross total resection (GTR, 97/249, 39.0%) were more common than biopsy (37/249, 14.9%). Awake procedures were performed in 25/173 (14.5%) cases. New permanent neurological deficits occurred in 24/254 (9.4%) patients. Median (IQR) follow-up was 57 (20-107) months. Individuals undergoing GTR or STR had longer median progression-free survival (PFS) than patients 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).

CONCLUSIONS

In this retrospective cohort of individuals with molecularly defined oligodendrogliomas, GTR was associated with prolonged PFS compared to biopsy without an observed increase in postoperative neurological deficits.