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BRAIN CANCERThe CyberKnife® Robotic
Radiosurgery System was cleared by the U.S. Food and Drug Administration in 1999 to treat tumors in the head and base of the
skull. Despite its name, the CyberKnife System is not a surgical procedure. In fact, there is no cutting involved. Instead,
the CyberKnife System delivers high doses of radiation directly to brain tumors. The CyberKnife System offers patients a non-invasive
alternative to brain cancer surgery, and can be used for brain tumors that are considered inoperable because of their location
in the head, for those patients who cannot undergo brain cancer surgery due to their poor medical condition, or who refuse
surgery. The CyberKnife System also can treat benign, or non-cancerous, tumors and other conditions, such as trigeminal neuralgia
and arterial venous malformations (AVMs). CyberKnife brain cancer treatments are typically performed on an outpatient
basis over a period of one to five days, requiring no overnight hospital stays. Most patients experience minimal to no side
effects with a quick recovery time.
What is Brain Cancer?Brain
cancer is an abnormal growth of cells in the brain, which result in a collection of cells called a brain tumor. If the abnormal
cells were originally brain cells that started to grow uncontrollably, it is a primary brain tumor. If the abnormal cells
originated in another part of the body, such as the lung or breast, and were carried to the brain by the blood or other body
fluid, then it is considered a metastatic brain tumor. More than 18,000 cases of primary brain tumors1 and more
than 170,000 brain metastases2 are diagnosed in United States each year.
Primary brain tumors
There are many types of primary brain tumors, including meningiomas,
pituitary adenomas, schwannomas and gliomas, which are divided into astrocytomas, ependymomas, medulloblastomas and oligodendrogliomas.
Each primary brain tumor is categorized based on the type of normal brain cell from which they originated and has its own
unique characteristics and growth patterns. Gliomas account for 40 percent of all primary brain tumors and it is common for
them to spread from the brain to other parts of the body1.The most aggressive type of glioma is called glioblastoma
multiforme2. Metastatic brain tumors
The cells that form metastatic brain tumors travel
to the brain from other parts of the body through the bloodstream, along nerves or within the fluid surrounding the spinal
cord and brain. These cells most commonly originate in tumors within the lung, breast, skin or colon, and are deposited in
the brain where they grow into a tumor.3 Both primary and metastatic brain tumors can be very dangerous because
they can compress sensitive brain tissue and nerves within the head, causing patients to experience symptoms such as vision
loss, hearing loss, difficulties with balance, pain or seizures. As these tumors grow larger, they can be life-threatening
because they disrupt critical parts of the brain that are responsible for breathing and other basic life functions.4
How is Brain Cancer Detected?Patients
with brain tumors may have symptoms such as headaches, seizures and other neurological problems. Because many of these symptoms
are not unique to brain tumors, it is difficult to make a diagnosis without some type of imaging study. Diagnosis often
involves visualization of the brain tumor by a physician using tools such as positron emission tomography-computed tomography
(PET-CT), Computed tomography (CT) scan or magnetic resonance imaging (MRI). Once the diagnosis has been made, more tests
may be necessary to identify the specific type of tumor and determine the proper treatment for the patient.
How is Brain Cancer Treated?The
treatment of brain tumors often requires combinations of several types of treatments to effectively fight the disease. Surgery:
For solitary tumors that are not near the brain’s most critical structures, such as those involved in vision or
regulation of breathing, the most common treatment option is surgery, in which the tumor is cut out through surgery.5
Surgery is used for primary brain tumors, such as a GBM, as well as solitary brain metastases and benign tumors. Surgery is
often followed by whole brain radiation therapy or partial brain radiation techniques to eliminate any microscopic bits of
the tumor. In some cases, malignant brain tumors can be treated in combination with chemotherapy for greater effect. Radiation
therapy:
If the patient suffers from multiple tumors, as is often the case with metastatic brain cancer, treatment
is often whole brain radiation therapy. Whole brain radiation treatment typically requires 20 to 40 sessions over four to
six weeks and is used to treat the entire brain, including both the tumor(s) and normal tissue. The normal brain tissue is
not as susceptible to small doses of radiation as the tumor cells, so the extended courses of whole brain radiation therapy
result in minimal destruction of normal brain cells for the patient. For patients with a limited number of tumors in
their brain, radiosurgery is another option.6 Chemotherapy:
Chemotherapy medication
is delivered orally or through an IV. It affects both normal tissue and the cancer cells, so patients may experience side
effects, such as severe nausea and vomiting, infections, fatigue and weight loss. Chemotherapy is typically given to a patient
in combination with other types of brain cancer treatment. For example, it may be given after whole brain radiation therapy
to target both the metastatic tumors in the brain and the tissues outside the brain that originally produced the cancer cells. Radiosurgery:
During the last 25 to 30 years, radiosurgery has emerged as an alternative to surgery.7-9 Unlike conventional
radiation therapy, during which small doses of radiation are delivered over weeks and months, radiosurgery can treat a tumor
in one to five sessions by delivering a high dose of radiation with extreme accuracy. During radiosurgery, hundreds of narrow
radiation beams are delivered from different angles, all intersecting at the tumor. This treatment allows the tumor to be
attacked by a high dose of radiation without damaging surrounding sensitive brain tissue. To be effective and safe, radiosurgery
must be accurate. To achieve this accuracy, some radiosurgery devices, such as the Gamma Knife®, require a rigid stereotactic
frame be affixed to a patient’s head so the system can pinpoint the exact location of a tumor.8 These frames
are screwed into a patient’s skull after local anesthesia is given. Many patients find these frames to be uncomfortable
and painful. In addition, if multiple treatment sessions are required, the patient may have to be hospitalized with the frame
in place for several days until the treatment is complete. Other radiosurgery devices, such as the CyberKnife Robotic
Radiosurgery System, improve on other radiosurgery techniques by eliminating the need for stereotactic frames. As a result,
the CyberKnife System enables doctors to achieve a high level of accuracy in a non-invasive manner and allows patients to
be treated on an outpatient basis.10, 11
How Does The CyberKnife® Treat Brain Cancer?The CyberKnife Robotic Radiosurgery System improves on
other radiosurgery techniques by eliminating the need for stereotactic frames. As a result, the CyberKnife System enables
doctors to achieve a high level of accuracy in a non-invasive manner and allows patients to be treated on an outpatient basis.10,
11 The CyberKnife System can pinpoint a tumor’s exact location in real time using X-ray images taken during the
brain cancer treatment that reference the unique bony structures of a patient’s head. The CyberKnife System has
a strong record of proven clinical effectiveness.12 It is used either on a stand–alone basis or in
combination with other brain cancer treatments, such as chemotherapy, surgery or whole brain radiation therapy. CyberKnife
brain cancer treatments involve a team approach, in which several specialists participate. The team may include: - a
Neurosurgeon
- a Radiation Oncologist
- a Medical Physicist
- a Radiation Therapist
- Medical Support
Staff
Once the team is in place, preparations begin for the CyberKnife treatment. Generally there are three steps
involved: - Set up and imaging
- Treatment planning
- CyberKnife treatment
Unlike other radiosurgery
systems – such as the Gamma Knife – the CyberKnife System does not require patients to be fitted with a rigid
and invasive head frame. In the set-up stage, the radiation therapist will create a soft mesh mask that is custom-fitted to
the patient’s face. This comfortable and non-invasive mask helps the patient keep his or her head and neck still during
treatment. While wearing the mask, a CT scan will be performed. The CT data then will be used by the CyberKnife team to determine
the exact size, shape and location of the tumor. An MRI, PET scan or angiogram also may be necessary to fully visualize
the tumor and nearby anatomy. Once the imaging is done, the face mask will be removed and stored until the CyberKnife treatment
begins. Then a medical physicist and the patient’s doctor use the data to custom-design the patient’s treatment
plan. The patient does not need to be present at this time. During the CyberKnife treatment planning phase, the CT,
MRI and/or PET scan data will be downloaded into the CyberKnife System’s treatment planning software. The medical team
will determine the size of the area that must be targeted by radiation and the radiation dose. They also will identify critical
structures where radiation should be minimized. Using this information, the CyberKnife System calculates the optimal radiation
delivery plan to treat the tumor. The treatment plan will take full advantage of the CyberKnife System’s extreme maneuverability,
allowing for a safer and more accurate treatment. After the brain cancer treatment plan is developed, the patient will
return to the CyberKnife Center for treatment. The doctors may choose to deliver the treatment in one session, or stage it
over several days. Typically, brain cancer treatments are completed within five days. For most patients, the CyberKnife treatment
is a completely pain-free experience. Patients dress comfortably in their own clothes and, depending on the treatment center,
they may be allowed to bring music to listen to during the treatment. Patients also may want to bring something to read while
they wait, and have a friend or family member with them to provide support before and after treatment. When it is time
for treatment, the patient lies on the table while their custom-fitted face mask is secured into place. The CyberKnife System’s
computer-controlled robot will move around the patient’s body to the various locations from which it will deliver radiation
to the tumor. Nothing will be required of the patient during the treatment, except to relax and lie as still as possible. Once
the CyberKnife treatment is complete, most patients quickly return to their daily routines with little interruption in their
normal activities. If the treatment is being delivered in stages, the patient will need to return for additional treatments
over the next several days, as recommended by their doctors. Side effects vary from patient to patient. Generally some patients
experience minimal side effects from CyberKnife treatments, and these often go away within a week or two. Prior to treatment,
the doctor will discuss with the patient all possible side effects they may experience. The doctor also may prescribe medication
designed to control any side effects should they occur. After completing CyberKnife radiosurgery treatment, it is important
that the patient schedule and attend follow-up appointments. They also must keep in mind that their tumor will not suddenly
disappear. Response to treatment varies from patient to patient. Clinical experience has shown that most patients respond
very well to CyberKnife treatments. As follow-up, doctors will monitor the outcome in the months and years following a patient’s
treatment, often using either CT scans and/or PET-CT scans.
1. CBTRUS, Primary Brain Tumors in the United States Statistical Report 1998-2002. 2006,
Central Brain Tumor Registry of the United States. (http://www.cbtrus.org/)
2. Khuntia, D., et al., Whole-brain radiotherapy in the management of brain metastasis.
J Clin Oncol, 2006. 24(8):
p. 1295-304.
3. Eichler, A.F. and S.R. Plotkin, Brain metastases. Curr Treat Options Neurol, 2008. 10(4): p. 308-14.
4. Andrews, D.W., Current neurosurgical management of brain metastases. Semin Oncol, 2008. 35(2): p. 100-7.
5. Black,
P., A. Golby, and M. Johnson, The emerging field of neurosurgical oncology: novel techniques to optimize outcomes and minimize
mishaps. Clin Neurosurg, 2007. 54: p. 36-46.
6. Tsao, M.N., et al., Whole brain radiotherapy for the treatment of multiple
brain metastases. Cochrane Database Syst Rev, 2006. 3: p. CD003869.
7. Leksell, L., The stereotaxic method and radiosurgery
of the brain. Acta Chir Scand, 1951. 102(4): p. 316-9.
8. Leksell, L., Stereotactic radiosurgery. J Neurol Neurosurg
Psychiatry, 1983. 46(9): p. 797-803.
9. Adler, J.R., Jr., et al., Toward an expanded view of radiosurgery. Neurosurgery,
2004. 55(6): p. 1374-6.
10. Naff, N.J., CyberKnife Radiosurgery in Neurosurgical Practice. Neurosurg Q, 2007. 17(4):
p. 273-282.
11. Hara, W., S.G. Soltys, and I.C. Gibbs, CyberKnife robotic radiosurgery system for tumor treatment. Expert
Rev Anticancer Ther, 2007. 7(11): p. 1507-15.
12. Chang, S.D., The CyberKnife: Potential in Patients with Cranial and
Spinal Tumors. Am J Cancer, 2005. 4(6): p. 383-393.
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