Gliomas are primary tumors that originate in brain parenchyma. Symptoms and diagnosis are similar to those of other brain tumors. Treatment involves surgical excision, radiation therapy, and, for some tumors, chemotherapy. Excision rarely cures.
Gliomas include astrocytomas, oligodendrogliomas, medulloblastomas, and ependymomas. Many gliomas infiltrate brain tissue diffusely and irregularly.
Astrocytomas are the most common gliomas. They are classified, in ascending order of malignancy, as
Low-grade or anaplastic astrocytomas tend to develop in younger patients and can evolve into glioblastomas (secondary glioblastomas). Glioblastomas contain chromosomally heterogeneous cells. They can develop de novo (primary glioblastomas), usually in middle-aged or elderly people. Primary and secondary glioblastomas have distinct genetic characteristics, which can change as the tumors evolve. Some astrocytomas contain oligodendroglioma cells; patients with these tumors (called oligoastrocytomas) have a better prognosis than those with pure astrocytomas.
Oligodendrogliomas are among the most benign gliomas. They affect mainly the cerebral cortex, particularly the frontal lobes. Some oligodendrogliomas are characterized by deletion of the p arm of chromosome 1 (1p deletion), deletion of the q arm of chromosome 19 (19q deletion), or both. These deletions predict longer survival and better response to radiation therapy and chemotherapy. Anaplastic oligodendrogliomas are a more malignant form of oligodendrogliomas and are managed accordingly.
Medulloblastomas and ependymomas usually develop near the 4th ventricle. Medulloblastomas develop mainly in children and young adults. Ependymomas, which are uncommon, develop mainly in children. Both types of tumors predispose to obstructive hydrocephalus.
Symptoms and signs vary by location (see Common Localizing Manifestations of Brain Tumors). Diagnosis is the same as that of other brain tumors.
Treatment involves surgery, radiation therapy, and chemotherapy to reduce tumor mass. Excising as much tumor as possible is safe, prolongs survival, and improves neurologic function.
After surgery, patients receive a full tumor dose of radiation therapy (60 Gy over 6 wk); ideally, conformal radiation therapy, which targets the tumor and spares normal brain tissue, is used.
For glioblastomas, chemotherapy with temozolomide is now routinely given with radiation therapy. The dose is 75/mg/m2/day (including weekend days when radiation is skipped) for 42 days, then 150 mg/m2 po once/day for 5 days/mo during the next month, followed by 200 mg/m2 po once/day for 5 days/mo in subsequent months for a total of 6 to 12 mo. During treatment with temozolomide, trimethoprim/sulfamethoxazole 800 mg/160 mg is given 3 times/wk to prevent Pneumocystis jirovecii pneumonia.
Patients receiving chemotherapy require a CBC at varying intervals.
Implantation of chemotherapy wafers during surgical resection may be appropriate for some patients.
Investigational therapies (eg, stereotactic radiosurgery, new chemotherapeutic drugs, gene or immune therapy, radiation therapy plus temozolomide) should also be considered.
After conventional multimodal treatment, the survival rate for patients with glioblastomas is about 50% at 1 yr, 25% at 2 yr, and 10 to 15% at 5 yr. Prognosis is better in the following cases:
With standard treatment, the median survival time is about 30 mo for patients with anaplastic astrocytoma and about 15 mo for patients with glioblastomas.
Treatment involves whole-brain radiation therapy using about 35 Gy, a posterior fossa boost using 15 Gy, and spinal cord radiation therapy using about 35 Gy. Chemotherapy may be given as adjunctive therapy and for recurrences. Several drugs are effective for certain patients; these drugs include nitrosoureas, procarbazine, vincristine alone or in combination, intrathecal methotrexate, combination chemotherapy (eg, mechlorethamine, vincristine [Oncovin], procarbazine, plus prednisone [MOPP]), cisplatin, and carboplatin. However, no regimen is consistently effective.
With treatment, survival rates are at least 50% at 5 yr and about 40% at 10 yr.
Usually, surgery to excise the tumor and open CSF pathways is done, followed by radiation therapy. For histologically benign ependymomas, radiation therapy is directed at the tumor; for more malignant tumors with residual tumor after surgery, whole-brain radiation therapy is used. For tumors with evidence of dissemination, radiation therapy is directed at the whole brain and spinal cord.
How much of the tumor can be excised may predict survival best. With treatment, overall 5-yr survival rate is about 50%; however, for patients with no residual tumor, the 5-yr survival rate is > 70%.