What is oligodendroglioma?
Oligodendroglioma is an uncommon type of primary brain tumor that comprises about 3 percent of all primary brain tumors diagnosed in the United States. Oligodendrogliomas contain cells that resemble normal oligodendrocytes but are more rapidly growing than normal cells. Like other brain tumor types, oligodendrogliomas are graded on a grade I-IV scale, with IV the worst. Grade II oligodendroglioma is a slow-growing tumor. Grade III oligodendroglioma, synonymous with anaplastic oligodendroglioma, typically grows more quickly. While some oligodendrogliomas are not malignant, they all have the potential to be.
Who is likely to have oligodendroglioma?
Oligodendroglioma can occur at any age, including childhood. These tumors are more common in men, with 35 to 40 being the average age of diagnosis.
What characterizes oligodendroglioma?
Symptoms depend on the location of the tumor within the brain. About half of oligodendroglioma patients experience seizures as the first symptom. Other symptoms may include headaches that are worse in the morning and improve during the day, mental or personality changes, nausea and vomiting, drowsiness, and vision problems. Oligodendroglioma can affect parts of the brain that control speech, vision or motor functions. For this reason, surgery may be associated with the risk of disability.
How does the pathologist make the diagnosis?
If brain tumor symptoms are present, your primary care physician performs a thorough neurological exam to check vision, hearing, balance, coordination and reflexes. To see inside the brain and locate the problem, the physician will order imaging tests such as magnetic resonance imaging (MRI), computed tomography (CT), or positron emission tomography (PET). A radiologist reviews these images and, in many cases, can diagnosis a tumor as malignant or benign using only these images. However, a definitive diagnosis and subclassification of a primary brain tumor is rendered by a pathologist, based upon the radiographic features and the microscopic study of the biopsied or resected tumor tissues.
It is important that a pathologist experienced in examining brain tumors performs this microscopic examination of your surgically resected tissues. Studies show that the diagnosis may change substantially for at least one-third of patients when an experienced pathologist does the review.
What is meant by the grade of the cancer?
The grade of a tumor refers to how benign or malignant it appears under the microscope and how aggressively the cells are growing. Tumors are graded on a grade I-IV scale, with IV the worst. In a grade I cancer, the cells look close to normal, with only slight abnormal changes. At this stage, the cells are slowly growing and indolent. Grade IV cancer cells bear little or no resemblance to normal cells, and the cells are growing quickly and are frankly malignant. Grades II and III describe conditions between these two extremes.
How do doctors determine what treatment will be necessary?
Your treatment will depend on the size, stage and location of the tumor, as well as your age. The pathologist consults with your neurosurgeon, radiation oncologist, and oncologist. Together, using their combined experience and knowledge, they determine treatment options most appropriate for your condition. It’s important to learn as much as you can about your treatment options and make the decision that’s right for you.
What kinds of treatments are available for oligodendroglioma?
Treating oligodendroglioma is a complex process, requiring a variety of techniques and procedures. The initial treatment often includes steroid medications to reduce swelling and inflammation of brain tissue, as well as anticonvulsant medications to prevent and control seizures if you have experienced them. If fluid has built up in the brain, a physician may insert a shunt—a long, thin tube that draws excess fluid from the brain.
Common treatments to remove or reduce the size of oligodendroglioma include surgery, sometimes combined with radiation therapy. Chemotherapy is used in addition to surgery and radiation therapy to treat patients with grade III anaplastic oligodendroglioma and in some cases of lower-grade oligodendroglioma, especially if the tumor has come back after initial surgical removal. To make sure that you receive treatment consistent with current best practices, you may wish to obtain a second opinion from a brain tumor specialty center for adults or children.
Surgeons work to remove as much of the oligodendroglioma as possible while trying to minimize damage to healthy tissue. Some tumors can be removed completely while others only partially or not at all. To gain access to the tumor, surgeons may cut bone from the skull in a procedure called craniotomy and replace the bone after the procedure. Some surgeons use a high-powered microscope (microsurgery) or computer programs that create 3-D maps of the tumor’s location; these maps help surgeons to remove tumors with minimal damage to healthy tissue and can reduce your pain and recovery time. In some situations, ultrasonic waves can be used to break apart the tumor, with the fragments removed by suction, in a procedure called ultrasonic aspiration. Sometimes, to prevent cancer from coming back, surgeons place chemotherapy-coated wafers in the space where a tumor has been removed.
Radiation therapy—pinpointed high-energy beams—can shrink tumors or destroy cancer cells remaining after surgery. This treatment is also an option if surgery is not possible. Radiation therapists sometimes use 3-D maps similar to what surgeons use to deliver radiation in the exact size and shape of the tumor.
In cases of anaplastic oligodendroglioma, a common treatment regimen involves radiation treatment combined with a chemotherapy drug called temozolomide (Temodar®), which makes the tumor more sensitive to the radiation therapy.
You may consider enrolling in a clinical trial testing new treatments. These treatments are highly experimental in nature but may be an option, especially for advanced cancers. Some trials may involve biologic therapy, which uses the natural defenses of the immune system to fight cancer. Clinical trials for oligodendroglioma may be found at www.cancer.gov/clinicaltrials or by calling NCI’s Cancer Information Service at 800-4-CANCER (800-422-6237) or NCI’s Neuro-Oncology Branch at 301-402-6298.
Current clinical trials for oligodendroglioma evaluate new procedures such as brachytherapy, stereotactic radiosurgery, and intraoperative radiation therapy. In brachytherapy, radiation therapists place materials that produce radiation (radioisotopes) directly into the tumor to destroy cancerous cells from the inside. In stereotactic radiosurgery, radiation therapy is used to damage cancer cells, taking away their ability to reproduce. Because the dose of radiation used in this procedure is designed to have minimal effect on normal tissue, this therapy is used to treat tumors that have tentacles reaching into parts of the brain that are difficult to reach. In intraoperative radiation therapy, the surgeon moves vital organs or tissue out of the way so that they will not be harmed by the radiation. In another new treatment being evaluated, radiation therapy is delivered in smaller, more frequent doses to lessen side effects.
What kinds of questions should I ask my doctors?
Ask any question you want. There are no questions you should be reluctant to ask. Here are a few to consider:
DEFINITION OF TERMS
Anaplastic: A descriptive term that is applied to tumors containing rapidly dividing cancer cells that bear little or no resemblance to normal cells.
Oligodendrocytes: Cells that support, nourish and protect nerve cells in the brain and spinal cord.
Primary Brain Tumor: A tumor that originates in the brain or spinal cord tissue rather than spreading to the brain from another part of the body.
Pathologist: A physician who examines tissues and fluids to diagnose disease to assist in making treatment decisions.
This information was developed by the College of American Pathologists’ Public Affairs Committee in conjunction with the College’s Cancer Committee and Council on Scientific Affairs. The College is providing this information to help you better understand your health. Ultimately any decisions you make about your health, however, should be between you and your doctor.