Brain Tumor Treatments
Once a brain tumor is diagnosed, the physician determines the best way to treat it. Often, surgery is the best option for removing as much of the tumor as possible. Radiation or chemotherapy may be used after surgery to destroy any remaining cells, or, in cases where the brain tumor is inoperable, may become the primary method of treatment.
Intraoperative MRI refers to the use of MRI technology to obtain images of the brain during surgery. Real-time visualization allows surgeons to confirm the location of lesions, plan and reconfirm the optimal surgical approach, and verify complete lesion removal prior to closure.
Conventional surgical navigation systems rely on images obtained prior to surgery and cannot account for movement of the brain during the surgery that could result simply from exposure or from tumor removal. With the use of MRI images obtained during various points in the surgery, the navigation system continuously adjusts to account for any brain shift, thereby minimizing harm to healthy and/or eloquent areas of the brain.
University Hospital is the hospital in the world to utilize a compact OR-based MRI system (PoleStar N-10) that successfully addresses the problems associated with early versions of intraoperative MRI systems, including cumbersome design, limited application, and high cost. The Brain Tumor Program is conducting clinical studies to confirm the efficacy of this revolutionary new technology.
The current gold standard in surgery involves the innovative use of stereotactic techniques. Instead of a “flat” image of the brain, computer-based technology provides a three-dimensional perspective to the surgeon.
Conventional stereotaxis attaches a metal frame to the patient’s skull to create a fixed reference point or system of coordinates. This fixed reference point, combined with a three-dimensional image of the brain provided by a computer and MRI scanning, allows for precise mapping and visualization of the tumor and surrounding tissue.
Once the brain has been mapped, precise navigation to the tumor site and optimal tumor resection is possible using a variety of surgical devices attached to the frame. The result is accurate, minimally invasive surgery that maximizes tumor resection, while minimizing injury to surrounding healthy tissue and functional losses in movement, sight, hearing, and speech.
Frameless Stereotactic Surgery
Frameless stereotactic surgery provides the same precision without the need to attach a heavy metal frame to the patient’s skull. Frameless systems substitute a reference system created by “wands,” plastic guides, or infrared markers. The Brain Tumor Program uses an infrared-based Stealth surgical navigation system for frameless, image-guided surgical approaches, and employs it when a frame-based system would be unnecessarily cumbersome or time consuming. Certain tumors-such as those with irregular margins-may be treated more effectively with the use of frameless stereotactic surgery.
The Stealth Station®, which works together with MRI, CT scans, or ultrasound, limits the size of cranial openings and removes much of the guesswork from cerebral localization. The Stealth uses sensor-based “optical tracking” computer technology to accurately pinpoint areas of the brain. It is precise within one millimeter. Images, produced in “real time,” are updated every eight seconds. This sophisticated system reduces surgical morbidity, operation time, and for some, length of hospitalization.
Surgical resection of a brain tumor is a common and often effective treatment. But sometimes the tumor’s location near “eloquent” areas of the brain-those that control movement or speech-poses a dilemma. Removing the tumor may also result in taking away some of the healthy tissue surrounding it, causing a neurological deficit.
The Brain Tumor Program is a pioneer in the use of Functional Image-Guided Surgery (FIGS), a technique that combines Functional MRI (fMRI) with frameless stereotactic surgery to optimize the safety and efficacy of treatment for patients with tumors located in the cerebral hemispheres.
During a FIGS procedure, fMRI is used to map the functional area of a patient’s brain. While the MRI is scanning, the patient is asked to perform a series of activities and movements, such as reading a list or tapping fingers. The areas of the brain that correlate to those movements “light up” on the scan and create an image. This information is sent to a surgical navigation computer located in the operating room. Neurosurgeons use a special pointer positioned on the patient’s head to guide incisions, skull openings, and brain tumors based on corresponding points of the MRI image. The added degree of precision in guidance and navigation provided by this technique maximizes tumor resection while minimizing the possibility of weakness, blindness, and speech loss.
FIGS offers non-invasive preoperative assessment and planning for brain tumor surgery. This technology also is being applied to stereotactic radiosurgery, where FIGS’ precision tremendously reduces the chance that radiation will be applied to eloquent areas of the brain.
MR SPECT is a new and highly effective method of scanning the brain. In many cases, it detects tumors that were unfound in earlier brain scans.
A conventional MR scan uses nuclear magnetic resonance imaging. This means that echoes of radio waves are sent to the brain to image a picture of the brain. As the radio waves encounter different densities, images are mapped out. Sometimes the images indicate masses or tumors. MR SPECT takes this mapping a step further and uses state of art software to analyze radio waves for signature patterns called spectra.
Different chemicals produce different types of spectra. So once the radio waves indicate a change in density, the spectra is analyzed. The presence of certain chemicals can tell physicians if there are tumors growing in the brain. The chemicals provide a more accurate indication for mapping. MR SPECT is a noninvasive test, that offers results in real time, decreasing the need for biopsies and other surgeries. It also offers physicians a quicker method of detection and enables treatment plans to be created sooner.
Skull Base Surgery
Many different types of tumors may be located at the brain’s undersurface, or skull base. Tumors in this area are not only deep-seated, they also are located near nerves associated with vision, hearing, and other functions. In the past, many of these tumors were considered inaccessible to the surgeon. Today, however, there are new approaches that enable neurosurgeons to remove skull base tumors without having to lift the brain. These operations, combined with advanced instrumentation and an emphasis on a multidisciplinary approach, have made skull base surgery a specialty in itself.
A comprehensive, “team” approach to skull base surgery is in place at University Hospital, and its importance cannot be overstated. With the skull base positioned near the eyes, ears, nose, and throat, there’s a need for specialists such as plastic surgeons, otolaryngologists, opthalomologists, neuroradiologists, and oncologists to be involved in the planning of the surgery and during the procedure itself. While one goal of the team is to remove as much of the tumor as possible, another is to retain the function of organs and nerves that may be affected by the surgery.
Plastic surgeons have adapted methods to skull base surgery that were initially used to repairing craniofacial deformities. Otolaryngologists, with their expertise in disorders of the head and neck, work closely with neurosurgeons in the care of patients with a range of anterior skull-based lesions. If a tumor is adjacent to an optic nerve, an opthalmolgist’s expertise may be needed to preserve the patient’s vision.
Stereotactic Radiosurgery (SRS)
Computer-based technology, which provides a three-dimensional perspective to the surgeon, is at the core of stereotactic techniques that are now the gold standard in brain tumor treatment. Not only can stereotaxis be used for conventional surgery, but also to deliver radiation to selected sites in the brain.
Stereotactic radiosurgery delivers focused, multiple beams of radiation to areas where they are needed-a single point on a tumor site-while avoiding healthy tissue. This procedure does not involve surgical incision and is often an excellent treatment alternative to surgery, or an option for patients who are not candidates for surgery. The Brain Tumor Program pioneered a radiosurgical technique that significantly reduces the treatment time required for complex lesions.
Stereotactic Radiation Therapy (SRT)
After surgical removal of a brain tumor, doctors want to make certain they have removed every tumor cell possible. Post-operative radiation treatments are commonly used to destroy microscopic cells or any part of the tumor that was inaccessible through surgery. Traditionally, radiation has been delivered to the whole brain-tumor site and normal tissue alike. But with today’s technology, the delivery of radiation can be focused on the tumor area.
Stereotactic radiation therapy uses frameless stereotaxis to deliver small doses of radiation therapy to tumor sites. Fractionated SRT is the method of delivering doses of radiation in daily treatments in order to increase the total amount of radiation directed to a tumor site.
Brachytherapy, or interstitial radiation, utilizes stereotactic techniques to implant radioactive “seeds” directly into a tumor. The seeds remain there for a period of time, enabling delivery of radiation across several stages of tumor growth and increasing the efficacy of treatment.
Stereotactic placement of brachytherapy sources is done in conjunction with physicians and assistance from radiation oncology.
GliSite® Radiation Therapy System
GliaSite is designed to be used after tumor removal surgery or tumor resection. After the surgery, an uninflated balloon catheter is placed inside the space left by the removed tumor (the tumor resection cavity). The other end of the catheter extends out under the scalp.
The balloon is filled with a solution (contrast medium) that is visible on an MRI. This allows the physician to verify that the balloon fits the cavity left by the resected tumor.
Once the patient has recovered from the tumor resection surgery, the contrast medium is removed from the balloon and a liquid radiation source is inserted into the catheter and into the balloon.
The radioactive fluid delivers radiation to the edges of the tumor cavity, targeting places where cancer may remain. It stays in the catheter for approximately three to seven days until the right amount of radiation is delivered. It is then removed from the catheter and then catheter is removed during a brief surgical procedure.
Because of the precision of the catheter, the risks to healthy tissue are minimized.
The Gliadel® Wafer
The Gliadel® Wafer is a complementary therapy used in the treatment of certain brain tumors. The Brain Tumor Program was part of a national study involving Gliadel and patients with recurrent glioblastoma multiforme (GBM) tumors. It currently is the principal investigator in a new multicenter study of the combined treatment of Gliadel, radiation therapy, and radiosurgery in patients with newly diagnosed malignant gliomas. Patients are being accepted into the trial study.
With the use of Gliadel in recurrent GBM tumors, up to eight dime-sized wafers are implanted following surgery. They slowly erode, delivering high concentrations of a chemotherapeutic drug, carmustine, at the tumor site. Because of the blood-brain barrier–a protective wall of blood vessels and cells–IV-delivered chemotherapy has difficulty reaching brain tumors. Additionally, Gliadel does not have the side effects commonly found with chemotherapeutic agents delivered through an IV.