Oligodendroglioma: An Analysis of Prognostic Factors and Treatment Results

This study, an analysis of variable prognostic factors affecting the treatment outcome for patients with oligodendroglioma, included a retrospective analysis of the medical charts of patients diagnosed with oligodendroglioma treated at our institution between 1975 and 1997. The endpoints analyzed were the progression-free survival (PFS), as well as the overall survival. The factors analyzed included extent of surgery, postoperative radiotherapy, pathologic grade, performance status, age, and sex. Of a total of 37 cases, 19 were male and 18 were female. The median age at diagnosis was 30 years. The most common presenting symptoms were headache (78%), seizures (43%), motor symptoms (38%), and to a lesser extent behavioral changes (16%). The median duration of symptoms was 9 months. The most common location on computed tomography or magnetic resonance imaging scans was the frontal region (43%). Low grade tumors (grades I and II) were found in 60% of patients, and the remaining 40% had high grade tumors (grades III and IV). Eight patients had complete surgical excision, whereas 27 patients had partial excision, and two patients had biopsy only. The operative mortality rate was 14%. There were 24 patients who received postoperative radiotherapy, and only 3 patients received adjuvant chemotherapy. The median postoperative radiation dose was 5,580 cGy. With a median follow-up of 7 years, the 5-year PFS and overall survival for the whole group were 58% and 67%, respectively. The pathologic grade of the tumor was the only prognostic factor significantly affecting both PFS and overall survival. The 5-year PFS for patients with low grade tumors was 79% in comparison to 32% for patients with high grade tumors (p < 0.01). Patients with good performance status at initial presentation (performance status of 1 and 2) had a higher 5-year PFS in comparison to those with poor performance status (62% vs. 38%, respectively); however, this difference did not reach statistical significance. Similarly, patients who were subjected to complete surgical excision had a marginally higher PFS in comparison to those who had biopsy or partial excision (75% vs. 53%). There was no difference in the 5-year PFS between patients who received postoperative irradiation versus those who did not (51% vs. 47%, respectively). Patients with high grade oligodendrogliomas have a relatively poor prognosis. The pathologic grade of the tumor was the single most important prognostic factor significantly affecting both the PFS and overall survival. A prospective randomized clinical trial is needed to address the impact of postoperative irradiation on PFS of those tumors. In view of the poor outcome for patients with high grade oligodendroglioma, the use of adjuvant systemic chemotherapy should be studied in future multicenter randomized trials.