Mixed oligoastrocytomas: a survival and prognostic factor analysis.

Seventy-one patients with supratentorial mixed oligoastrocytomas underwent surgery only (5 patients) or surgery with postoperative radiation therapy (66 patients) between 1960 and 1982. The median survival for these 71 patients was 5.8 years and the 5-, 10-, and 15-year survival rates were 55, 29, and 17%, respectively--values significantly different from those of an age- and sex-matched normal reference population. Uni- and multivariate survival analyses were applied to 14 possible prognostic factors, including the following: patient factors--age, sex, and seizures; tumor factors--site, size, side, computed tomographic enhancement, and calcification; pathological factors--tumor grade and dominant cellular component; and treatment factors--extent of surgical resection, lobectomy, and radiation dose and field. Of these factors, tumor grade, as determined by the Kernohan method, was the most strongly associated with survival. The 60 patients with Grades 1 and 2 tumors had a median survival of approximately 6.3 years and 5- and 10-year survival rates of 58% and 32%, respectively, compared with 2.8 years (36 and 9%, respectively) for the 11 patients with Grades 3 and 4 tumors. Age < 37 years, gross total resection, partial brain radiation, and radiation dose > or = 5000 cGy were other factors significantly associated with improved survival in both uni- and multivariate models. Three of five patients not receiving postoperative radiation therapy experienced tumor recurrence and died. Seven of eight patients from whom tissue was obtained at the time of tumor progression demonstrated anaplastic transformation.(ABSTRACT TRUNCATED AT 250 WORDS)