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Oligodendroglioma

 

Definitions

  • 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.
  • Malignant: Cancerous.
  • Primary brain tumor: A tumor that originates from cells within the brain or spinal cord tissue rather than from a tumor that spreads to the brain from another part of the body. 
  • Pathologist: A physician who examines tissues and fluids, usually under the microscope, to diagnose disease in order to assist in making treatment decisions. 

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 age 35 the average age of diagnosis.

What characterizes oligodendroglioma?

Symptoms depend on the location of the tumor within the brain. About half of oligoden-droglioma 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 pre-sent, 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 determine if a tumor is most likely malignant or benign using these images. However, a definitive diagnosis and sub-classification of a primary brain tumor is rendered by a pathologist, based upon the microscopic examination of the tissue biopsy/resection material.

It is important that a pathologist experienced in examining brain tumors performs this review. 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 a microscope and how aggressively the cells are growing. In a grade I tumor, the cells look close to normal, with only slight abnormal changes. At this stage, the cells are slow-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, grade, 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, some-times combined with radiation therapy. Chemotherapy is used in addition to surgery and radiation therapy to treat patients with grade III Anaplastic oligodendro-glioma 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 proce-dure. Some surgeons use a high-powered microscope (micro-surgery) 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 pre-vent 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 brain tumors evaluate various chemotherapy treatments, as well as new procedures such as brachytherapy, stereotactic radiosurgery, and intra-operative 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.

For more information, go to www.cancer.gov (National Cancer Institute) or www.abta.org (American Brain Tumor Association). Type the keywords oligodendroglioma or brain tumor into the search box.

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:

  • Please describe the type of cancer I have and what treatment options are available.
  • What is the grade of the cancer?
  • What are the chances for full remission?
  • What treatment options do you recommend? Why do you believe these are the best treatments?
  • What are the pros and cons of these treatment options?
  • What are the side effects?
  • Is your medical team experienced in treating the type of cancer I have?
  • Can you provide me with information about the physicians and others on the medical team?
  • If I want a second opinion, could you provide me with the names of physicians and/or institutions that you would recommend?