Radiation Treatments for Brain Tumors
Treatment for brain tumors depends on a number of factors including the type, location and size of the tumor as well as the patient's age and general health. Brain tumors can be benign or malignant, primary or metastatic. Even if the tumor is benign, many patients suffer from symptoms if a brain tumor goes untreated. Historically, brain tumors have
been treated first with surgery. However, in many cases, surgery isn't possible because of the location of the tumor. And with the advances in radiation therapy and radiosurgery, more and more patients are able to have their tumors treated without undergoing an invasive surgery.
Sometimes the whole brain is given radiation, sometimes only a limited area. When the whole brain needs radiation treatments for brain metastases, treatments are usually given daily Monday through Friday for two to three weeks. Some patients can be treated with radiation therapy first, and then radiosurgery, or radiosurgery alone.
Treatment Techniques
There are two broad categories of radiation therapy; both are designed to target the tumor precisely while minimizing exposure to the healthy surrounding tissue. In the first category - external beam radiation therapy - the radiation is delivered by a machine called a linear accelerator, or linac, which focuses a high-energy x-ray beam into the tumor site from outside the body. In the second treatment category, the radiation is delivered by radioactive material placed inside the body near the cancer cells — a procedure called brachytherapy (also called implant radiation therapy or internal radiation therapy).
External Beam Radiation Therapy
IGRT, or image-guided radiation therapy, uses sophisticated computer software to analyze a series of image scans of your tumor to create a detailed, three-dimensional picture of the site and your surrounding tissues. The scans typically are produced by computed tomography (CT scan), magnetic resonance imaging (MRI), or positron emission tomography (PET scan). Image-guidance technology enables your team to view the tumor and its position in your body before and during each treatment.
VMAT, or volumetric modulated arc therapy, uses special software and an advanced linear accelerator to deliver treatments up to eight times faster than what was previously possible with standard radiation therapy. Unlike conventional treatments, during which the machine must rotate several times around the patient, or make repeated stops to treat the tumor from a number of different angles, VMAT can deliver the dose to the entire tumor in a single rotation — in as little as two minutes.
IMRT, or intensity modulated radiation therapy, involves changing the intensity of the radiation beam at various angles. At each of these angles, the intensity of the radiation is varied (modulated) and the shape changed to suit the shape of the tumor. This directs the prescribed amount of radiation to each part of the tumor, and minimizes exposure to the surrounding healthy tissue.
Radiosurgery is a medical procedure that allows non-invasive treatment of benign and malignant tumors. It is also known as stereotactic radiosurgery (SRS) when used to target tumors in the brain and spine, and stereotactic body radiotherapy (SBRT) when used to target tumors in the body. Radiosurgery uses similar technology to other radiation treatment techniques but differs from conventional radiation therapy treatments in two important ways:
- Rather than having treatment five days a week for 4 to 6 weeks, radiosurgery is delivered in a few very large radiation doses given in five or fewer sessions over one to two weeks.
- Because each treatment delivers very high doses of radiation, the requirement for precision and accuracy is much greater (millimeters vs. centimeters) than conventional treatments. Most radiosurgery techniques to spine are given in one session.
Until recently, radiosurgery was most often used when the patient could not undergo conventional surgery to remove the tumor(s) because of its size or location, or because the person's health was too poor for surgery. However, some physicians consider radiosurgery as the first line of treatment for some tumors.
Internal Radiation Therapy or Brachytherapy
Low-dose brachytherapy (internal radiation therapy) is not a very common technique for treating brain tumors, but may be used in some cases during surgery if it is difficult for the physician to define the outermost edge of the tumor. This procedure involves placing very small radioactive seeds near the tumor site in order to disrupt the growth of any cancerous cells that may remain in the area where the tumor was removed.
