The prognostic impact of prior low grade histology in patients with anaplastic gliomas: a case-control study

At the time of recurrence, the majority of low-grade cerebral gliomas transform to a higher grade of histologic malignancy. The purpose of this study was to determine the survival outcome for patients whose anaplastic gliomas began as low-grade tumors compared with patients with de novo high-grade gliomas. Seventy-seven (11.5%) of 667 patients with anaplastic gliomas consecutively treated at the University of Alabama at Birmingham had histologically proven prior low-grade tumors. As a group, the patients with prior low-grade tumors would be expected to have a relatively favorable outcome, as they were younger and had a lower proportion of glioblastoma multiforme than the patients with de novo anaplastic gliomas. The provide a valid comparison, we performed a matched case-control study. We matched 68 patients from the prior low-grade group one-to-one with patients from de novo group for tumor histology, age, Karnofsky performance scores, and type of surgery, without knowledge of outcome. The two groups received comparable radiotherapy and chemotherapy. For the 68 patients with prior low-grade tumor, median actuarial survival from the time of diagnosis of malignant degeneration was 19.7 months and the 5-year survival rate was 22%, compared with 22.0 months and 28% for the 68 matched de novo patients. Kaplan-Meier survival curves for the two group did not significantly differ (p = 0.24 by logrank test). There were no significant survival differences between the patient subsets of prior low-grade versus de novo with glioblastoma, anaplastic astrocytoma, or anaplastic oligodendroglioma/mixed anaplastic glioma. The data indicate that the currently available treatment options, the survival outlook for patients with anaplastic gliomas, whose tumors arose from transformation of low-grade gliomas, is equivalent to the prognosis for patients with de novo anaplastic gliomas.