OBJECTIVES: I. Compare survival and time to first progression in patients with anaplastic oligodendroglioma treated with radiotherapy with or without adjuvant procarbazine, lomustine, and vincristine (PCV) following surgical resection. II. Investigate the effect of PCV on quality of life and neurologic function in these patients. III. Determine the toxicity of PCV in these patients. IV. Correlate chromosomal lesions (1p and/or 19q, 9p, p53 loss and mutation, amplification of chromosome 7, or loss of chromosome 10) with progression-free and overall survival in patients treated with these regimens.