Refer to the PDQ summaries on Childhood Astrocytomas Treatment and Childhood Brain Stem Glioma Treatment for more information.
The most common genetic alteration in oligodendroglial tumors is LOH on the long arm of chromosome 19q, the incidence of which ranges from 50% to more than 80%. The second most common genetic alteration in oligodendroglial tumors is LOH on the short arm of chromosome 1p. Specific chromosomal abnormalities involving deletions of both 1p and 19q have been identified for a subset of oligodendroglial tumors, which have a good response to lomustine, procarbazine, and vincristine (PCV) therapy.[13,14] Median postoperative survival times have been reported to range from 3 to 10 years for all histologic grades of oligodendroglial tumors.
Oligodendroglioma (WHO grade II) is a well-differentiated tumor, composed predominantly of cells morphologically resembling oligodendroglia, which grows diffusely in the cortex and white matter. This tumor accounts for approximately 50% of oligodendroglial tumors and between 5% and 18% of all gliomas. Most oligodendrogliomas occur in adults, with a peak incidence in the fifth and sixth decades of life. Compared to patients with astrocytoma, patients with oligodendroglioma respond better to radiation therapy and chemotherapy. Temozolomide appears to have activity in low-grade oligodendrogliomas and oligoastrocytomas combined with a 1p allelic loss. Clinical improvement was noted in 51% of patients, and the radiologic response rate was 31%.[Level of evidence: 3iiiDiv]
Anaplastic oligodendroglioma (WHO grade III) is an oligodendroglial tumor with focal or diffuse histologic features of malignancy and a less favorable prognosis than grade II oligodendroglioma. Approximately 50% of oligodendroglial tumors are anaplastic oligodendrogliomas. These types of tumors manifest mainly in adults and occur primarily in the frontal lobe and secondarily in the temporal lobe. In a study of 39 patients, chemotherapy was effective in tumors with a chromosomal abnormality (i.e., an allelic loss at 1p and 19q, which is present in 65% of tumors) with a response rate to combination therapy with procarbazine, lomustine, and vincristine (PCV) approaching 100%. The 5-year survival rate in this group was 95%.[18,19][Level of evidence: 3iiiDiv]
(Refer to the Oligodendroglial Tumors section of this summary for treatment information.)
Oligoastrocytoma (WHO grade II) is composed of two distinct neoplastic cell types that morphologically resemble tumor cells in oligodendroglioma and diffuse astrocytoma. Estimates of incidence vary greatly. In one large U.S. study, only 1.8% of gliomas were classified as mixed gliomas. The median age of patients is reported to range from 35 years to 45 years. This tumor has a predilection for the cerebral hemispheres; the frontal lobes are most commonly affected, followed by the temporal lobes. These types of tumors contain no specific genetic alterations or chromosomal abnormalities; however, about 30% of oligoastrocytomas have genetic aberrations commonly found in astrocytic tumors. One study reported a median survival time of 6.3 years. Temozolomide appears to have activity in low-grade oligoastrocytomas and oligodendrogliomas combined with a 1p allelic loss. Clinical improvement was noted in 51% of patients, and the radiologic response rate was 31%.[Level of evidence: 3iiiDiv]