stereotactic radiosurgery

F O C U S I N G O N T R E A T M E N T

StereotacticRadiosurgery

A Word About ABTAFounded in 1973, the not-for-profit AmericanBrain Tumor Association has a proud history offunding research, providing patient services, andeducating people about brain tumors. Our mission is to eliminate brain tumors throughresearch and to meet the needs of brain tumorpatients and their families.

We gratefully acknowledge Walter Curran, MD,Professor and Chairman, Department ofRadiation Oncology, Thomas Jefferson UniversityHospital; Clinical Director, Kimmel CancerCenter of Jefferson Medical College; Director,Jefferson Cancer Network; and Group Chairmanof the Radiation Therapy Oncology Group(RTOG) for his assistance in writing this publication. We also appreciate the efforts of Shari Rudoler, MD for the original edition.

This publication was made possible throughthe generosity of Loma Linda UniversityMedical Center, Department of RadiationMedicine, Loma Linda, California and IntegraRadionics, Burlington, Massachusetts.

ISBN 0-944093-75-2

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| 1STEREOTACT IC RAD IOSURGERY

What Is StereotacticRadiosurgery?Stereotactic radiosurgery is a special form of radiation therapy - it is not surgery. Stereotacticradiosurgery allows precisely focused, high doseX-ray beams to be delivered to a small, localizedarea of the brain. It is used to treat small brain andspinal cord tumors (both benign and malignant);blood vessel abnormalities in the brain; definedareas of cancer; certain small tumors in the lungsand liver; and neurologic problems such as movement disorders. In this publication, weaddress radiosurgery only as used for braintumors.

Despite the use of the word, there is no surgery involved in this form of radiationtherapy.

What is RadiationTherapy?The radiation treatments used for brain tumorsare very similar to the radiation you know as atreatment for cancer in other parts of the body.When radiation is used to treat brain tumors, thegoal is to slow, or arrest the tumor growth.Radiation either kills tumor cells directly or itinterferes with their ability to grow. Radiation isnot completely selective, however. It can affectboth normal cells and tumor cells. Because of this,scientists worked to develop a special type of radiation that focuses the high-dose zone of radiation just on the target area. This focusedform of radiation is called radiosurgery.

STEREOTACT IC RAD IOSURGERY2 |

Radiosurgery is DifferentFrom ConventionalRadiation Therapy Conventional external beam radiation therapy –the most common form of radiation therapy –delivers full dose radiation to the tumor and someof the surrounding brain tissue. For several reasons, the target area for conventional radiationdeliberately includes a border (called a “margin”)of normal brain around the tumor. These reasonsinclude uneven tumor borders, the risk of invisiblespread of the tumor into the surrounding tissue, alarger tumor size, or the presence of multipletumors. This larger zone of full-dose radiationincludes the borders of the tumor where microscopic tumor cells may be located.

Since normal brain tissue is included in the full-dose region, conventional radiation is brokendown into small daily doses so the normal braintissue can tolerate it. As a result, reaching thedesired dose of radiation takes several weeks ofdaily treatment.

Radiosurgery focuses radiation beams more closely to the tumor than conventional externalbeam radiation. This is possible through the useof highly sophisticated computer-assisted equipment. A head frame or facemask used forthis treatment allows very precise set up,localization and treatment of the tumor. Usingadvanced computer planning, radiosurgery minimizes the amount of radiation received bynormal brain tissue and focuses radiation in thearea to be treated.

Since conventional radiation therapy covers morenormal tissue, it can often be given only once.Radiosurgery, however, may be considered for re-irradiation due to its precision and the possibility of avoiding previously treated areas.


Types of RadiosurgeryEquipment There are three general types of equipment usedto deliver radiosurgery: a system with fixedradioactive source, such as the Gamma Knife; linear accelerators; and cyclotrons.

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The Gamma Knife is a dedicated radiosurgeryunit containing two hundred and one cobalt-60

radiation sources which canall be computer-focused ontoa single area of the brain.

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Linear accelerators are the machines used to deliver conventional external beam radiation

therapy. A linear acceleratorcan be modified to deliver a single high-energy computer-shaped beam tothe tumor, or the liner accelerator may have beenmanufactured specifically for use in radiosurgery.

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Cyclotrons are nuclear reactors capable of smashing atoms to release proton, neutron and

helium ion beams that can beharnessed for radiosurgerypurposes. There are only afew of these machines in use.


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Names of RadiosurgeryEquipmentSeveral companies manufacture radiosurgeryequipment and the software for these computer-based systems. Each company gives their radiosurgery system a brand name, much in thesame way an automobile manufacturer namestheir cars. For example, GE, Radionics, Accurayand BrainLab are companies that manufacture linear accelerator-based radiosurgery systems orsoftware. Each manufacturer names their equipment: the X-Knife, Stealth Station,CyberKnife, and Novalis System are some of the brand names of linear-accelerator-based radiosurgery systems or software.

Each system has some inherent differences in the way the planning is done or the radiation is delivered, each with its own advantages and disadvantages. At this time, there is no definitiveproof that one system is better than another.

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The Gamma Knife is a radiosurgery system with a fixed source of energy. In this system, the radioactive cobalt-60 sources used to produce the radiation beams remain in one place while thepatient is moved on a sliding couch toward the source of the radiation.

STAR (Stereotactic Alignment for Radiosurgery),Conforma 3000, and PROBEAT are systems usedto deliver proton beam radiosurgery. Protonbeams are created by a cyclotron (a nuclear reactor) which smashes atoms, releasing the protons used in this therapy.

You may have also heard the term “stereotacticradiotherapy.” Stereotactic radiosurgery is given ina single session. If given in multiple sessions, thetreatment may be called stereotactic radiotherapyor fractionated stereotactic radiotherapy.

“Frameless radiosurgery” refers to radiosurgerythat does not use a metal frame to immobilize thehead during treatment. Rather, markers able to beviewed on a scan are placed on the scalp, or a facemask is used to help hold the head steady. Thetreatment equipment is then aligned with themarkers or with the face mask.

The Goals ofRadiosurgeryIn general, the purpose of any form of radiationtherapy is to shrink and destroy tumor cells. Sometumors can be cured by radiation therapy, whileothers may be controlled. There are situationswhere a tumor does not shrink in response toradiosurgery but is still cured. This is a commoncircumstance for patients with certain benignbrain tumors.


Because radiosurgery is a highly-focused treatment, this form of radiation therapy is usefulin situations where the tumor is small and contained in a localized area. Although the definition of “small” may vary slightly from institution to institution, “small” tumors are generally considered to be those 3 cm (about 1¹ ⁄₄ inches) or less in diameter.

Radiosurgery can be used for tumors in the brainor in the spinal cord. It may be used to treat multiple tumors if the tumors are small and thereare a limited number. Sometimes, radiosurgery isused to treat tumors that cannot be removed, orthose that can be only partially removed. Also,radiosurgery may be used as a local “boost” at the end of conventional external beam radiation therapy.

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How is RadiosurgeryGiven?There are several techniques used to deliverradiosurgery. In the paragraphs that follow, wedescribe a typical day of treatment using the morecommon types of radiosurgery equipment.Although the equipment or method you see mayvary, the goal of the treatment is the same.

Your first contact with the radiosurgery unit will likely be with one of the members of the radiosurgery team. Radiosurgery requires a team of specialists. That team may include a neurosurgeon, radiation oncologist, radiologist,radiation physicist, neurologist, anesthesiologist,specially trained nurses, technologists and the unitsupport staff. Members of the team first reviewyour medical records to decide if radiosurgerywould be of benefit to you. If it is determined thatradiosurgery is an option and you consent totreatment, the next steps will be obtaining therecords and scans needed to plan your personal-ized treatment. Your recent MRI scans, a currentscan or additional images, biopsy or surgicalreports, pathology reports, and specially designedplanning software are used to precisely determinethe plan for treating your tumor. The radiosurgeryteam calibrates the equipment to match your

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personalized treatment plan, including the area tobe treated and the dose of radiation to be given. Ingeneral, the area radiated includes the abnormalarea with a tiny margin of surrounding normal tissue. The dose of radiation is centered over theentire volume of the target area. The radiationdose decreases rapidly as the distance away fromthe target area increases.

Before the treatment, your team may prescribemedications such as steroids (which prevent brainswelling) or anti-seizure drugs (which controlseizures). The staff at the radiosurgery unit willalso provide you with specific instructions to follow in preparation for your treatment. Be sureto tell them — in advance — about all of the medications you are using including prescriptiondrugs, over-the-counter medications, vitamins,dietary supplements, or herbal preparations. Theywill tell you which drugs to continue, and whichto stop prior to treatment. You will also receiveinformation about your diet the day prior to thetreatment, any special shampoo instructions forthe evening before, the time and location of yourappointment, and transportation guidelines. Planto bring someone with you to drive you home.

When you arrive at the radiosurgery unit for yourtreatment, you may have an IV (intravenous) linestarted to help prevent dehydration. If you havequestions, remember to ask them before any relaxing medication is given to you. This willallow you to better understand the answers.

Most forms of radiosurgery require placement of alightweight headframe, also called a “halo.” Theheadframe has two functions. It helps your doctordefine the exact location of the tumor, and it willkeep your head immobilized so that there is nomovement during treatment. The headframe isattached the day of your treatment. Your doctorwill first inject a local anesthetic into your scalp atthe places where the pins will be placed. Thisanesthetic is a “freezing” medication similar tothat used by your dentist. Once the scalp is


numbed, screws or pins are positioned. Thosepins will hold the headframe in place during thetreatment planning and actual treatment. Placingthe pins and positioning your headframe can takeseveral hours, depending on the technique used.If your treatment will be given in more than onesession, computerized markers may be used toexactly match the previous pin locations. Or, theheadframe may be attached to your head with amouthpiece that is custom made for you, andallows exact reproduction of the position of theframe during each session.

Those being treated with proton beam radiosurgery may befitted with a moldedplastic face mask,which serves the same purpose as aheadframe. If yourradiosurgery is to be done with a“frameless” system,you may also be fittedfor a face mask.Low-dose x-rayimages will be taken to continually trackyour position duringtreatment.P R E PA R I N G A

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Once the headframe or facemask is in position,MRI and/or CT scans will be done with the headframe on. You will then be able to rest whilethe treatment plan is calculated by the radiosurgeryteam. Your physician may give you a mild sedativeto help you relax during this planning time andthe subsequent treatment.

For Gamma Knife treatment, you will be placedon a couch, and then a large, oversized helmet willbe attached over your headframe. Open holes inthe helmet allow computer-programmed beams tomatch the shape of your tumor. The entire couch(with you securely on it) is then slid into a dough-nut hole shaped piece of equipment calleda “gantry” through which the radiation beams are delivered.

If you are treated with a linear accelerator, you willbe positioned on a sliding bed around which thelinear accelerator circles. There are two commontechniques by which linear accelerators deliverradiosurgery. One is by directing many arcs ofphoton beams at the target area. The pattern ofthe arc is computer-matched to the shape of yourtumor. The second technique is to deliver theradiosurgery by a series of shaped “fixed” fieldsand not arcs. In some cases the radiation dose

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pattern is shaped by varying the intensity of radiation through these fields. This technique of varying the intensity is known as “intensitymodulated radiation therapy” or IMRT.

For proton beam-basedradiosurgery, you willusually be positionedon a table with yourhead in a fitted face-mask or a frame. As thenuclear reactor smashesatoms, the releasedprotons are directedtoward the tumorthrough beam-shapingblocks. The beams arecomputer-programmedto match the shape ofyour tumor.

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The actual treatment time for any of these techniques generally ranges from 15 minutes toabout two hours. After you receive your treatment,the headframe is removed. Generally, you returnhome the same day or you may be kept overnightfor observation. The radiosurgery team will provide you with instructions for caring for yourself in the next few days, and for your followup visit with your own physician. Most people feel able to resume their usual activitieswithin a day or two.

If you are to receive multiple treatments, these will be done on an “outpatient” basis. You will be given a schedule of appointments, and your headframe or mask will be repositioned each timeyou receive treatment.

After you complete your treatments, you shouldfeel free to contact the radiosurgery team with anyquestions or concerns. Unless your team instructsyou differently, the doctor coordinating your usualbrain tumor care is the doctor with whom youmake your followup appointments. A scan will bedone in a few months to evaluate the initial effectof the treatment, but it may take a year (sometimeslonger) to truly evaluate the full effect of the treatment.

Side Effects of TreatmentWhen your treatment planning is first done, yourradiosurgery team can talk with you about thepotential effects of the treatment specificallyplanned for you. Some people have few or no sideeffects from this type of radiation therapy. Oncethey have rested following the treatment and haveresumed their regular activities, tenderness at thepin sites may be their only side effect. Your doctorcan suggest pain medications if needed, or perhaps a topical gel to help numb the pin siteuntil it heals. Other people have reactions whichvary from early side effects to delayed reactions.


Early symptoms are often due to brain edema(swelling) caused by the radiation. These symptoms can include nausea, vomiting, dizziness,or headaches. Your doctor can prescribe steroids,anti-nausea drugs or pain relievers to control thesesymptoms, which are usually temporary. Once theswelling resolves, these symptoms usually resolve.

Two to three weeks after treatment, you may experience hair loss in the area radiated, but thisdoes not occur in everyone. Hair loss depends onthe dose of radiation received by portions of thescalp and the ability of the radiated hair follicles toheal. Regrowth usually begins in 3-4 months, andmay be a slightly different color or texture thanbefore. Your scalp may also become temporarilyirritated. Since some lotions cause further irritation, do not treat this yourself. Call yourradiosurgery team for advice.

Some patients may experience delayed reactionsweeks or months after treatment. These reactionscan include necrosis or cell death in the high radiation dose region due to swelling in reactionto the radiation effect on the target region. Thesesymptoms are mainly due to swelling or death ofbrain tissue in the treated area. They may mimicthe symptoms of tumor regrowth or stroke.Treatment will be based on the type of side effectthat occurred. Other effects depend on the location of the tumor. All treatments, even thoseclaiming to be “natural therapies,” have the potential for serious or life-threatening effects.When your doctor discusses the possible sideeffects of the treatment planned for you, askher/him to help you weigh the benefits of thetreatment against the risks.

To Learn MoreThis pamphlet is part of our Focusing onTreatment series of publications. Other publications in this series include Steroids,Surgery, Conventional Radiation Therapy and


Chemotherapy. In addition, we offer publicationsand resources that explain the different types ofbrain tumors, treatment options, supportresources, and the latest news in brain tumorresearch. To access these free services, please visit our web site at www.abta.org, or call us at800-886-2282.

It is our hope that the information in this pamphlet helps you communicate better with thepeople who are treating you. Our purpose is notto provide answers; rather, we encourage you to ask questions.

Photo CreditsWE THANK THE FOLLOWING CORPORATIONS AND INSTITUTIONS WHOGRACIOUSLY PROVIDED PHOTOS TO ENHANCE THIS PUBLICATION.

PAGES

03, 04 Gamma Knife image courtesy of Elekta Instruments

03, 04 ONCOR Linear Accelerator image courtesy of Siemens Medical Solutions

03, 04 Gantry of proton beam unit image courtesy of Loma Linda University Medical Center, Loma Linda, California

05 CyberKnife image courtesy Accuray, Incorporated

07 Novalis Shaped Beam Surgery System image courtesy of Mount Sinai Medical Center, New York City, New York

08 Radiosurgery planning images courtesy of BrainLab AG

10 Preparing a face mask image courtesy of Loma Linda Medical Center, Loma Linda, California

10 Face mask in place image courtesy of Accuray, Incorporated

11 Gamma Knife helmet image courtesy of Elekta Instruments

12 ConforMAX headframe image courtesy of Integra Radionics

12 Delivering proton radiosurgery image courtesy of The Frances H. Burr Proton Therapy Center at Massachusetts General Hospital, Boston


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