Precise Radiation for Brain/CNS Cancer
While relatively rare, and often curable, finding the right therapy to treat tumors in the brain or central nervous system (CNS) can be challenging. Treatment usually requires surgery, followed by radiation therapy to destroy any remaining cancer cells. However, older radiation delivery methods can expose nearby, healthy tissue to damage.
Cutting-edge therapies such as Intensity Modulated Radiation Therapy (IMRT) and Image-Guided Radiation Therapy (IMRT) offered by Rainier Cancer Center enable physicians to deliver higher doses of precisely focused radiation to cancerous tumors while sparing nearby healthy tissue. This is particularly significant in the brain where critical structures may be at risk.
What Is Brain/CNS Cancer?
The central nervous system (CNS) is the medical name for the brain and spinal cord. Brain/CNS tumors are masses of abnormal cells in these areas that have grown out of control. There are two types of tumors. Primary tumors start in the brain/CNS and can be benign (non-cancerous) or malignant (cancerous). Metastatic tumors start in other parts of the body, most often the lungs, breast and colon, and spread (metastasize) to the brain/CNS. They are always malignant.
Most primary brain tumors can spread through the brain, but rarely spread to other areas of the body. However, even if a primary brain tumor is benign it presents a significant risk. As tumors grow they can compress normal brain tissue causing damage that can be disabling or even fatal. For this reason, physicians often speak of brain “tumors” and not brain “cancer.” The main concern with brain tumors is how quickly they spread to other parts of the CNS and how thoroughly they can be removed.
The four major categories of brain tumors include:
- Metastatic – the spread of cancer from one organ or part of the body to the brain and central nervous system.
- Gliomas – which occur in the glial cells that help support and protect critical areas of the brain. About 4 in 10 brain tumors are gliomas (includes benign and malignant tumors).
- Meningiomas – which are slow growing tumors that affect the meninges—the tissue that forms the protective outer covering of the brain. Twenty-five percent of all brain/CNS tumors are meningiomas and up to 85% of them are benign. They don’t typically produce symptoms, but if detected can be successfully treated with surgery.
- Schwannomas – which occur in the sheath that covers nerve cells. Vestibular schwannomas, (also known as acoustic neuromas) are responsible for hearing. These are typically benign and respond well to surgery.
- Medulloblastomas – which are common brain tumors in children. They grow quickly, and invade neighboring parts of the brain and CNS.
Who Gets Brain/CNS Cancer?
According to the American Cancer Society, the chance that a person will develop a malignant tumor of the brain or spinal cord is less than 1% (about 1 in 150 for men and 1 in 182 for women). Brain/CNS cancer accounts for about 1.5% of all cancers and 2.3% of all cancer-related deaths. The number grows significantly when benign tumors are factored in.
Most brain tumors are random, meaning they have no known cause. The most significant risk factor is exposure to radiation, either on the job or as cancer treatment. Other risk factors include:
- Cancer from another location – many cancers located elsewhere in the body have a tendency to spread to the brain.
- Immune system disorders – people with impaired immune systems have an increased risk of developing lymphomas of the brain or spinal cord.
- Genetic syndromes – people with rare cases of brain neurofibromatosis type 1 & 2 (NF1 & NF2), tuberous sclerosis, von Hippel-Lindau disease, Li-Fraumeni syndrome, Gorlin syndrome, Turcot syndrome, and Cowden syndrome may be more susceptible to developing brain tumors.
- Other environmental factors – some believe that there are other environmental factors, particularly cell phone use, but this is undocumented.
Some tumors are more prevalent by age and gender. For instance, meningiomas are twice as prevalent in women as in men and occur primarily on those over age 65. Medulloblastomas are typically found in children and are slightly more common in boys.
How Do I Know If I Have Brain/CNS Cancer?
There are no tests for the early detection of brain/CNS cancer. However, survival is more dependent on age, tumor type and location than on early detection.
Tumors typically are discovered as symptoms arise. Symptoms vary depending on the location and size of the tumor. Most are caused by pressure as tumors grow and include:
- frequent headaches.
- blurry vision.
- nausea and/or vomiting.
- personality or cognitive changes.
Other symptoms are site-specific or tumor-specific and include seizures; speech impairment; weakness or numbness on one side; problems with coordination, balance or mobility; and ringing in the ears (vestibular schwannomas/acoustic neuromas).
There are several tests physicians can use to further the diagnostic process and look for Brain/CNS cancer. MRI and CT scans often can show exactly where a brain tumor is located. PET scans can provide information about whether suspect areas are likely to be cancer. After treatment, they can tell whether cancer cells have been killed and whether abnormalities that may show up on MRI or CT are scar tissue or tumors that have grown back.
The only way to know for sure if a brain/CNS tumor is cancerous is with a biopsy or lumbar puncture (spinal tap). With a biopsy a sample of the tumor is removed surgically or with a needle and sent to the lab to be examined under a microscope. With a lumbar puncture cerebrospinal fluid is extracted to look for cancer cells.
What Are My Treatment Options?
Physicians use the results of diagnostic tests to determine the site of the cancer and to stage it—or tell how far it has spread. This helps determine the outlook for recovery and the best course of treatment. Because brain/CNS tumors are often located near critical and/or sensory organs, patients should work together with their physician to choose among several treatment options that may be used alone or together, and understand the risks and benefits of each.
Surgery is the most common treatment for brain/CNS tumors, and often provides a cure. The goal is to remove as much of the tumor as possible without affecting brain function, often followed by radiation therapy to kill any remaining cancer cells. For tumors that have spread diffusely into nearby brain tissue, the goal of surgery is to reduce the amount of tumor that will need follow-up treatment with radiation or chemotherapy. Surgery can also help with symptoms related to the pressure of the tumor.
Chemotherapy (also called “chemo”) employs oral or injected drugs to kill cancer cells. These drugs enter the bloodstream and travel throughout the body, making the treatment useful for cancers that have spread to distant organs. However, many chemotherapy drugs are not able to enter the brain and reach tumor cells. For some brain/CNS tumors, the drugs may be given directly into the cerebrospinal fluid in the brain or into the spinal canal below the spinal cord. For brain/CNS tumors, chemotherapy is typically used along with other types of treatment such as surgery and/or radiation therapy.
Because chemo kills some normal cells in addition to malignant ones, it can cause side effects that vary depending on the type of drug used. These include, but are not limited to, fatigue, nausea, vomiting, loss of appetite, hair loss, mouth sores, changes in menstrual cycle and infertility. It can also cause low white blood cell and platelet counts resulting in higher risk of infection and easy bruising/bleeding. Although rare, some chemotherapy drugs used for brain/CNS tumors cause kidney damage and hearing loss.
Researchers are learning more about the gene changes in cells that cause cancer, enabling them to develop new drugs that specifically target these changes. These drugs work differently than standard chemotherapy drugs, usually with less severe side effects.
Stereotactic radiosurgery is a highly precise form of radiation therapy used primarily to treat small tumors and other abnormalities of the brain. It is a non-surgical procedure that delivers a single, high dose of precisely-targeted radiation using highly focused gamma-ray or x-ray beams that converge on the specific area(s) of the brain where the tumor or other abnormality resides, minimizing the amount of radiation to healthy brain tissue.
Radiation that kills or shrinks tumors may be used alone or in combination with other treatments, particularly to kill any cancer cells that remain after surgery. For brain cancer, radiation is typically a secondary therapy, but may be used as a primary treatment for brain tumors in difficult or critical locations in the brain. It can be delivered internally or externally. Side effects are usually limited to irritation around the radiation site, although many patients also report fatigue.
Brachytherapy With brachytherapy, radioactive seeds (pellets) are placed into directly into or near the tumor. The seeds give off small amounts of radiation over several weeks, and may be complemented by low doses of external radiation to treat nearby areas. This radiation method carries small risks associated with seed migration within the body.
External-Beam Radiation Therapy External-beam radiation is much like getting a regular x-ray, but with a much higher dose of radiation. Precisely-focused beams of radiation are focused on the affected area from outside the body. Therapy is administered five days a week for a defined number of weeks, depending on the size, location and type of tumor. This schedule allows enough radiation to get into the body while giving healthy cells time each day to recover. The treatment itself takes only minutes and is usually painless, but the proximity of tumors to critical structures in or near the brain can limit the effectiveness of traditional radiation therapy. External-beam radiation has been proven to be very successful in palliative treatment for cancer of the brain.
IMRT/IGRT are rapidly replacing traditional external-beam radiation therapy for treating certain cancers. With daily CT guidance, they allow for more precise delivery of higher radiation doses to cancerous brain tumors while avoiding healthy brain and critical structures. IMRT/IGRT can also potentially shorten the duration of therapy and enable physicians to treat some brain/CNS tumors for which traditional radiation therapy was not an option.
Your Brain/CNS Cancer Treatment Partner
At Rainier Cancer Center, we offer patients a variety of treatment options, from traditional radiation to cutting-edge therapies such as IMRT/IGRT that may not be widely available in other treatment centers. Regardless of the treatment path, we pride ourselves on providing each patient with the best outpatient experience in the most comfortable atmosphere. Treating Brain/CNS cancer can be a complicated process, so our personal Cancer Navigators help guide each patient through their journey.
IMRT & IGRT: Fighting Brain/CNS Cancer with Precision
Quick and painless, external-beam radiation has long been used to destroy cancer cells. The latest methods—Intensity Modulated Radiation Therapy (IMRT) and Image-Guided Radiation Therapy (IGRT)—provide the most advanced technology for fighting cancer. Used alone or together, these therapies allow higher doses of radiation to be delivered with greater precision and accuracy without destroying surrounding, healthy tissue. For instance, IGRT allows for the safe delivery of higher doses of radiation when the tumor is close to the brain stem, optic nerve and optic chasm.
For patients, IGRT means:
- more effective treatment focused on cancer cells.
- less radiation exposure to normal tissue.
- potentially fewer and milder side effects.
- treatment for some tumors that couldn’t previously be treated by radiation.
How IMRT Works
IMRT is a specialized radiation therapy that uses powerful treatment planning software to calculate precise beam angles, shapes and exposure times tailored to each tumor. The radiation beam can be broken up into many smaller beams and the intensity of each small beam can be adjusted individually. This may allow a higher dose of radiation to be delivered to the tumor with less risk to nearby healthy tissue, potentially decreasing the duration of treatment and increasing the chance of a cure.
How IGRT Works
Tumors can move during a course of treatment. IGRT combines imaging and treatment capabilities on a single machine. This way, tumors can be tracked between, as well as during, treatments, allowing radiation to be focused more precisely. Images captured before each radiation session are compared to previous sessions so that clinicians know the exact location of the tumor each time. IGRT software also accounts for breathing and motion during treatment, ensuring the radiation stays focused on the tumor.
External-Beam Radiation Therapy
When IMRT/IGRT is not an option, Rainier Cancer Center can also provide traditional radiation therapy to patients with brain/CNS tumors. Like a regular x-ray, radiation beams are focused on the affected area from outside the body. It can be used alone or in combination with other therapies.
What to Expect During Treatment
The treatment process is similar for IMRT, IGRT and traditional external-beam radiation therapy.
First, we’ll schedule an appointment with a radiation oncologist. During this visit, we’ll perform a simulation of the treatment. You will be positioned on the treatment machine the same way you will be for actual treatment. The radiation oncologist will determine the need to use an immobilization device (such as a cast, mold or headrest) to keep you in the same position during treatment. Then, we’ll take a CT scan to precisely map your anatomy. Using information from the CT scan, the radiation therapist will mark the area(s) to be treated, either on your skin or on the immobilization device. Simulation sessions take 30 to 60 minutes and may be repeated at intervals throughout your course of treatment.
Next, your radiation oncologist and treatment team will design a treatment plan tailored to you. They will use information from the simulation session, anatomical maps obtained from the CT scan, previous medical tests and, in many cases, sophisticated treatment planning software.
For brain/CNS cancer, radiation therapy is typically administered 5 days per week. The number of weeks will vary widely and will be determined by your radiation oncologist. During each session, positioning takes from 5 to 15 minutes. Actual treatment time lasts about 10 minutes and is painless. The radiation is delivered using a machine called a “linear accelerator” which generates x-rays or photon radiation. The linear accelerator moves so that patients can lie comfortably without being re-positioned during treatment.
The treatment room is spacious, and you will not be completely enclosed by equipment. A radiation therapist will position you to ensure successful treatment then go to an adjoining control room. From there, he or she will monitor you closely during radiation treatment using video cameras. The therapist can hear you at all times, and the treatment can be immediately discontinued if you feel uncomfortable or ill. If IMRT/IGRT are employed, the therapist may move the machine or treatment table during treatment to best target the exact area of the tumor. Once each treatment is complete, you can return to your normal daily activities.