There are two types of brain tumors. Primary brain tumors arise from the tissues which make up the brain and its coverings. Primary brain tumors may be malignant or benign. Secondary, or metastatic brain tumors, travel to the brain from cancerous tumors elsewhere in the body. Metastatic tumors are always malignant. The most common sources of metastatic tumors are cancers of the lung, breast, skin (melanoma), kidney and colon.
The treatment of malignant tumors to the brain is complex. Once a cancerous tumor spreads to the brain, there are several options for control or cure. These options include open surgery, whole brain radiation therapy, chemotherapy and radiosurgery. These options are often used in a combined approach to treatment.
Conventional whole brain radiation therapy has been used for more than 60 years to treat brain metastases. The entire brain is radiated using small doses of radiation, or fractions, each day for a number of weeks. This gradually builds up a dose large enough to effect tumor growth. Because the normal brain tissue is sensitive to radiation, the total dose given to the tumor is limited for whole brain radiation. Side effects are common: loss of hair, at one end of the spectrum of complications, and dementia and other brain injury at the other end of the spectrum of complications. Continued tumor growth and the development of new metastases are not unusual after whole brain radiation therapy because of dose limitations.
The concept and techniques of radiosurgery were developed by Professor Lars Leksell in Sweden many years ago. Dr. Leskell is the inventor of the Gamma Knife. Radiosurgery avoids many complications and limitations of whole brain radiation therapy. Radiosurgery is more effective and convenient. Instead of radiating the whole brain, radiosurgery is specifically targeted treatment of the metastatic tumor. This means only the tumor receives a therapeutic dose of radiation, while the surrounding normal brain receives little or no toxic radiation. This also means the dose given to the tumor can be much greater (and effective) than the dose of radiation possible with whole brain radiation. However some patients require whole binary radiation therapy. Your doctor will discuss with you whether you need whole binary radiation, gamma knife or both.
Radiosurgery is usually carried out in a single fraction on an out-patient basis. Patients can return to normal activities the day following Gamma Knife radiosurgery. Unlike whole brain radiation therapy, radiosurgery can be repeated should additional metastases appear or the original tumor continues to grow. We expect that 90% of metastatic tumors treated with radiosurgery will show no further growth, and many or most tumors will disappear. Radiosurgery can be performed by linear accelerator systems adapted to radiosurgery, proton beam systems, and the Leksell Gamma Knife. Dr. Leksell actually envisioned and developed all of these methods of treatment, but ultimately selected the Gamma Knife because of its accuracy, effectiveness, and ease of use. It is the only radiosurgical device solely dedicated to use for tumors of the brain. (Other systems are adaptations of machines used for conventional radiotherapy.) Its design of focused sources of gamma rays, and fixed frame-based radiation delivery define the standard for radiation accuracy. This is critical for small tumors near important neural structures.