Successful treatment of low-grade oligodendroglial tumors with a chemotherapy regimen of procarbazine, lomustine, and vincristine.

Anaplastic oligodendroglioma (OD) tumors, especially those with the combined loss of the short arm of chromosome 1 (1p) and the long arm of chromosome 19 (19q), are sensitive to chemotherapy. Only limited data are available on the role of chemotherapy in low-grade OD. The authors retrospectively studied the outcome of the procarbazine, lomustine, and vincristine (PCV) chemotherapy regimen in a group of 16 patients with newly diagnosed OD and 5 patients with recurrent low-grade OD. Two groups of patients were studied: newly diagnosed patients with large OD and mixed oligoastrocytomas (OA) and patients with recurrent OD and OA after radiotherapy who still showed nonenhancing tumors. Treatment consisted of standard PCV chemotherapy. In the newly diagnosed and responding patients, radiotherapy was withheld until the time of disease recurrence. Responses were assessed by T2-weighted magnetic resonance image (MRI) scans. Loss of chromosome 1p and 19q was assessed using fluorescent in situ hybridization with locus-specific probes. Three of five patients with recurrent tumors responded. Thirteen of the 16 newly diagnosed patients showed evidence of response. The median time to disease progression in this group was >24 months. Only one of these patients experienced disease progression while receiving chemotherapy. Several patients showed a signficant clinical improvement despite only a modest improvement of the tumor on the MRI scans. Even patients without loss of 1p or 19q showed satisfactory responses. No TP53 mutations were found. Newly diagnosed patients with OD tumors, with or without loss of 1p/19q, responded to PCV chemotherapy. Up-front chemotherapy may be indicated especially for patients with large tumors. MRI scans were of limited value for the assessment of response. A Phase III trial should be initiated to compare radiotherapy with chemotherapy.