Oligodendroglioma: does deferring treatment compromise outcome?

This study reports the University of Florida experience treating oligodendrogliomas with the goal of identifying the factors that predict favorable outcome. Between 1958 and June 1998, 51 patients (aged 5-75 years) were diagnosed with pure oligodendroglioma at the University of Florida. Histologic grade was anaplastic in 19 patients, low-grade in 30 patients, and unknown in one patient. Twelve patients were treated with surgery alone (10 with low-grade tumors). Thirty-nine patients underwent postoperative radiotherapy after surgery (plus chemotherapy in four patients). A biopsy was performed in 10 patients, 40 underwent subtotal or gross total resection, and one had surgery of unknown extent. Thirteen patients with a radiographic abnormality consistent with a low-grade glioma had the initiation of definitive treatment (i.e., surgery with or without radiotherapy) deferred for a median of 4.5 years before undergoing treatment for worsening symptoms or radiographic progression. Absolute survival for the entire group (51 patients) at 5, 10, and 20 years from the date of initial treatment was 61%, 37%, and 31%, respectively, and at 5, 10, and 20 years from the date of initial diagnosis was 65%, 43%, and 34%, respectively. No patient died of intercurrent disease. Multivariate analysis for absolute survival from the time of initial treatment demonstrated young age (young patients fared better than older patients) and size (<5 cm better than > or =5 cm) to be significant variables. No patient under the age of 21 years (n = 8) at the time of diagnosis has died in this series. Deferring aggressive treatment did not alter survival. Multivariate analysis for favorable absolute survival based on the time from initial diagnosis demonstrated young age and presentation with seizures alone to be statistically significant for favorable outcomes. Approximately one third of patients with oligodendroglioma appear to be cured with aggressive treatment. Age is the most important predictor of long-term progression-free and absolute survival with young patients (especially aged <21 years) doing much better than older patients. Deferring aggressive treatment (surgery and/or radiation) until symptoms clearly indicate tumor progression does not compromise outcome for a select group of patients who are diagnosed at a young age with a nonenhancing mass on MR and seizures as the lone presenting symptom.