Primary brain tumors are the most common solid tumors occurring in children. Between 2,500 and 3,500 children and teens are diagnosed with brain tumors in the United States each year. Because there are many different kinds of brain tumors, the number of children diagnosed with each particular type is small. The incidence of brain tumors is higher in males than females and higher among white children than black children.

Description

Describing the various brain tumors is difficult because there is no universally accepted system for categorizing them. Generally, however, most tumors are named for the type of cell from which the cancer originated and the location of the tumor in the brain. The most common pediatric brain tumors are astrocytoma, medulloblastoma, brain stem gliomas, ependymomas, and optic nerve gliomas.

• Astrocytomas.  Astrocytomas are tumors that arise from star-shaped cells called astrocytes. Low-grade astrocytomas grow slowly, and many types have a favorable prognosis. High-grade astrocytomas grow quickly and are more difficult to treat.

• Medulloblastomas.   Medulloblastomas are fast-growing, malignant tumors that are usually located in the cerebellum. They are diagnosed most often in children between the ages of 4 and 8 and are more common in boys than girls.

• Brain stem gliomas.  Brain stem gliomas are slow- or fast-growing tumors that occur equally in both sexes and are most common in children between the ages of 5 and 10.

• Ependymomas.  Ependymomas are tumors that usually grow on the internal surfaces of the brain and spinal cord and are often benign. Ependymomas in the brain occur most often in children younger than age 10; those of the spinal cord usually strike children older than age 12.

• Optic nerve gliomas.  Optic nerve gliomas are tumors located along the optic nerves, the optic chiasm, and the hypothalamus.

Brain tumors can be benign (noncancerous) or malignant (cancerous). Treatment of both benign and malignant brain tumors can result in numerous late effects.

Treatment

Treatment for brain tumors usually is some combination of surgery, radiation, and chemotherapy. In some cases, stem cell transplantation is also used. If the tumor is benign, surgery may remove it completely. Whether the tumor is benign or malignant, its location in the brain usually determines how it is treated.

Surgery

Surgery has many uses in the treatment of brain cancers. It is used to get a sample of tissue to confirm the diagnosis, remove as much of the tumor as possible, or alleviate symptoms. For some brain tumors, surgery is used to place a shunt to drain fluid from the brain. There are some instances when surgery is not possible due to the location of the tumor and the damage that would be done to the child’s ability to function by trying to remove it.

After surgery for brain tumors, physicians classify, grade, and stage the tumor before deciding on what further treatment, if any, is necessary. Each step of this process is explained in the following list:

• Classification.  A pathologist looks at a sample of the tumor under a microscope to determine the origin of the tumor cells. For instance, tumors that arise from glial cells in the brain are ependymomas, astrocytomas, and oligodendrogliomas.

• Grading.   The pathologist estimates the degree of the malignancy by studying many different features of the tumor cells. Numbers are used to describe the aggressiveness of the tumor, with the higher numbers being the more aggressive. Tumors are assigned a grade of I, II, III, or IV. Some brain tumors do not get a grade because they are always considered to be aggressive (for instance, medulloblastoma). Aggressive means they will grow and spread if left untreated.

• Staging.  Before surgery, the extent of the tumor spread is evaluated using scans. During surgery, the neurosurgeon decides whether the tumor can be completely removed (called resected) and whether other tumors are present. For most tumors, doctors recommend a lumbar puncture to check for cancer cells in the cerebrospinal fluid. The doctor will determine how many additional studies, if any, are needed after surgery to stage the tumor.

After the tumor has been classified, graded, and staged, the oncologist gives recommendations for treatment.

Radiation

Radiation therapy—directing high-energy x-rays at tissue—is frequently used for brain tumors. In most cases, the radiation is directed at the tumor itself, sparing surrounding healthy tissue as much as possible. To minimize damage to healthy brain cells, 3-dimensional conformal radiation therapy or charged-particle radiation therapy (such as proton beam therapy) are being used at many cancer treatment centers around the country. Research is currently underway with children to examine the acute and long-term effects associated with this new way to deliver radiation. For extremely malignant tumors, the entire cranium and sometimes the spine are irradiated to destroy any cancer cells that have broken off from the main tumor and lodged elsewhere.

Radiation is generally given in many doses (called fractions) over a period of time. The length of radiation treatment and the amount of radiation given varies depending on the type of tumor, its location in the brain, and the child’s age. Because of the critical brain growth that would be disrupted in young children, doctors try to postpone or avoid using radiation until children are at least 2 years old.

Chemotherapy

Chemotherapy has variable effectiveness against brain tumors because the blood-brain barrier prevents many types of chemotherapy from penetrating brain tumors. In some cases, chemotherapy is used in very young children to slow the progression of their disease until radiation can be given with fewer long-term side effects. In other cases, chemotherapy is one of the front-line treatments used to cure disease.

Stem Cell Transplantation

Autologous bone marrow transplants and peripheral blood stem cell transplants have been used with increasing frequency to treat children with high-risk or relapsed brain tumors. Descriptions of the types of stem cell transplants and their late effects are at the end of this chapter under “Stem cell transplantation.”

Late effects

This section briefly outlines some common and uncommon late effects from treatment. Remember that you may develop none, one, or several of these problems in the months or years after treatment ends.

The brain is the master of thoughts, emotions, and actions. All treatments for brain tumors can result in major effects on thinking and functioning. Following are brief descriptions of some of the more common known late effects after treatment for brain tumors. Of course, the specific treatment used (i.e., surgery, radiation, chemotherapy), the age of the child, and the location of the tumor determine the types of late effects that are likely to develop.

Learning disabilities. Both surgery and radiation can damage a child’s CNS. When whole brain radiation is used, it can have profound effects on how well the brain functions. The amount of damage depends on the child’s treatment, age, and sex, with younger female children more at risk than males and older children or teens. Learning disabilities can develop years after treatment ends, and social functioning is often impacted as well. For more information, see Chapter 8 .

Growth and hormonal problems. Radiation can also affect growth. Children who receive more than 2400 cGy of cranial radiation or spinal radiation often fail to grow normally. Radiation can cause early or delayed puberty, thyroid problems, and other hormonal imbalances. For more information, see Chapter 9 .

Hearing loss and kidney damage. Cisplatin can cause significant hearing loss and kidney damage. For more information, see Chapter 10 , and Chapter 14 .

Hepatitis C. Infection with the hepatitis C virus can develop in survivors who had blood transfusions prior to July 1992. For more information, see Chapter 15 .

Other late effects. Radiation to the head can also cause cataracts and, rarely, secondary cancers. For additional information, see Chapter 10 and Chapter 19 .