When considering treatment options for a patient with brain metastases, physicians weigh a range of factors — the number of lesions, the location within the brain, the state of the patient's systemic disease, and his or her overall health. Considered together, these factors determine the optimal treatment for each patient.
Treatments for metastatic brain lesions include surgery, radiation therapy, and sometimes chemotherapy. These therapies may be delivered alone or in combination. Patients also often receive steroids (such as dexamethasone) to reduce the swelling, or edema, within the brain. Doctors at Memorial Sloan-Kettering use all of these treatments and are also conducting clinical trials to assess new chemotherapy agents for brain metastases.
For some patients with one or two brain lesions, surgery may be the best treatment option, as long as the tumors can be reached without causing extensive damage to healthy tissue. Neurosurgeons remove as much of the tumor as possible and at the same time release pressure within the skull caused by the tumor. Improvements in surgical techniques — particularly image-guided stereotaxy — have revolutionized brain surgery in recent years.
- Intraoperative Imaging Suite
To improve the success of brain surgery, Memorial Sloan-Kettering's neurosurgeons perform brain surgery in an intraoperative imaging suite that has a MRI scanner in the operating room. At any point during surgery, the neurosurgeon can rotate the patient into the MRI machine to determine whether the tumor has been removed completely. If any residual tumor is found, surgery can be resumed, and the remaining tumor detected in the scan is removed. Being able to reevaluate the patient's tumor with MRI during surgery allows neurosurgeons to operate with increased precision and will reduce the need for — and risk of — a second operation.
- Image-Guided Stereotactic Surgery
Image-guided stereotactic surgery, also called frameless stereotaxy, is a very precise method of operating on deep-seated brain structures that is based on the idea that all points on the brain can be described using a three-dimensional system of coordinates. Stereotaxy allows surgeons to better plan operations in advance and provides enhanced orientation and guidance during surgery.
Before the procedure, technicians attach six plastic self-adhesive dots around the patient's scalp, and an MRI is performed. At the start of surgery, the exact location of these dots is registered and used to relay the position of the patient's head to the surgical navigation system.
The team directs a wand-like viewing device at the patient's brain that simultaneously projects an image onto a monitor in the operating room. The image is synchronized with the MRI scan taken immediately before surgery. This image gives the neurosurgeon up-to-the-moment orientation as he or she plans an approach through healthy tissue to remove the tumor. Also, the neurosurgeon can use the viewing wand to help see through the tumor to its margins (the outermost edges of the tissue that is being removed) during the operation, helping to ensure that all visible tumor has been removed.
Frameless stereotaxy is used in conjunction with Memorial Sloan-Kettering's intraoperative MRI.
- Functional Imaging & Intraoperative Brain Mapping
Functional imaging and intraoperative brain mapping have greatly improved the safety of brain tumor surgery. Functional magnetic resonance imaging (fMRI) uses high-speed MRI to map areas of the brain associated with vision, speech, touch, movement, and other functions, the locations of which can vary from one person to the next. Using the map as a guide, the surgeon can plan surgery to avoid disrupting these important areas so as to minimize the effects of surgery.
Many of our brain tumor operations are performed while the patient is awake but sedated. During intraoperative brain mapping, the neurosurgeon electrically stimulates the brain in the area around the tumor using small electrodes while asking the patient to talk, count, look at pictures, and perform other basic tasks. This process helps our surgeons locate the “eloquent” regions in the brain, which govern speech, the senses, and movement, and a map is created of the areas where preserving brain tissue is an absolute necessity. Surgeons can then avoid these sensitive tissues while removing as much of the tumor as possible.
This kind of sophisticated brain mapping allows the neurosurgeon to remove tumors that are otherwise deemed inoperable, while maximizing preservation of the patient's normal function.
Some procedures are now performed using neuroendoscopy, in which the neurosurgeon works through a small opening in the skull using a thin tube with a powerful lens and high-resolution video camera to see into the skull and brain. Advantages of this minimally invasive neurosurgical procedure include a small incision site, the enhanced ability of the surgeon to perform microsurgical procedures, and the potential for less trauma to healthy tissue.
Following surgery, an MRI is performed to determine the extent of tumor removal and to help plan further treatment.
New methods of radiation therapy allow doctors to raise the dose of radiation delivered to a metastatic brain tumor, while enhancing precision and minimizing the amount of radiation that reaches healthy tissue.
These technological advances rely on Memorial Sloan-Kettering's team approach to cancer care, involving specialists in radiation oncology, neurosurgery, medical physics, and neurology, whose combined expertise is critical to ensure that the treatment is delivered most effectively and with a minimum of damage to healthy brain tissue.
IMRT & IGRT
Our physicians are working to develop new techniques to further improve the targeting accuracy of radiation therapy and to minimize its side effects. Our radiation oncologists use intensity-modulated radiation therapy (IMRT), which allows more precise treatment planning and the ability to deliver higher radiation doses with greater safety. With IMRT, radiation therapists can shape pencil-thin radiation beams of varying intensity to conform to specific tumor shapes and sizes, reducing the dosage of radiation to healthy tissues and possibly the side effects of treatment. In addition, an enhanced form of radiation therapy known as image-guided radiation therapy (IGRT) is used to treat brain tumors. By incorporating real-time image guidance within IMRT, radiation oncologists can make adjustments in the radiation beam so that radiation is delivered with even more precision.
Stereotactic Radiation Therapy
Memorial Sloan-Kettering radiation oncologists use a micro-multileaf collimator system for radiosurgery and also for more conventional radiation treatments. In this type of radiation therapy, the radiation beam is covered by many layers of what are called multileaves that shape the beam to the outline of the tumor, as interpreted by an MRI scan. Radiation is then delivered with great precision only to that tissue. The radiation beam is conformal (meaning that the instrument looks at the tumor in three dimensions and shapes the radiation beam to its outlines) and intensity modulated (the beam moves so that it spreads the radiation dose, and no area gets too large a dose).
The conformal radiotherapy method used for stereotactic radiosurgery treats brain tumors that are four centimeters (about an inch and a half) or less in diameter, including malignant gliomas, acoustic neurinomas, meningiomas, and brain metastases. The instrument is very precise and fashions the radiation dose closely to tumor boundaries, sparing the surrounding brain tissue from any significant dose of radiation.
Stereotactic radiosurgery may be used to treat most patients with three or fewer smaller brain tumors. Candidates for stereotactic radiosurgery include those whose lesions are not surgically accessible, who cannot tolerate anesthesia, or whose systemic disease is too advanced for neurosurgery.
Whole-Brain Radiation Therapy
When patients have large lesions deep in the brain or many lesions throughout the brain, whole-brain radiation therapy is the best treatment option. The treatments are administered over a course of weeks to minimize side effects.
Investigators here are also assessing the effectiveness of stereotactic radiosurgery following surgical removal of metastases, to see if this combination of treatments is a more effective way to prevent metastases from recurring.
Because most metastatic brain tumors do not respond to chemotherapy, chemotherapy is rarely part of the treatment regimen. However, there is increasing recognition that many standard chemotherapeutic agents work against brain metastases in some patients.
For example, a few chemotherapeutic agents, such as temozolomide, are effective in some patients with brain metastases. Temozolomide has shown effectiveness against some forms of primary brain tumors because the oral chemotherapeutic agent is able to cross the blood-brain barrier — the protective shield formed by special cells lining the capillaries in the brain that prevents many cancer drugs from penetrating to brain cells. All brain metastases have an abnormal blood-brain barrier that allows at least partial penetration of drugs into the tumor even if the agent cannot reach the healthy brain tissue. This is the reason an increasing number of drugs, such as temozolomide, are recognized as working against brain metastases.
Memorial Sloan-Kettering physicians are currently testing new agents specifically targeting brain metastases in clinical trials.