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PROSTATE CANCERThe CyberKnife® Robotic
Radiosurgery System was cleared by the U.S. Food and Drug Administration in 2001 to treat tumors anywhere in the body, including
the prostate. 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 the prostate cancer. The CyberKnife System offers
patients a minimally invasive, alternative prostate cancer treatment. Prostate cancer treatments with the CyberKnife System
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 Prostate Cancer?The
prostate is a male sex gland that is about the size of a walnut. It produces a thick fluid that is a normal component of semen
in men. Prostate cancer is the most common cancer among men in the United States after non-melanoma skin cancer, and is the
third leading cause of cancer-related deaths. Prostate cancer is expected to be diagnosed in 186,320 men in 2008. 1
Because of widespread screening efforts, the majority of newly diagnosed prostate cancers are found early when they are still
confined to the prostate gland, thus the number of prostate cancer-related deaths has decreased.
How is Prostate Cancer Detected?Prostate cancer is usually detected with a combination of a prostate-specific
antigen test (i.e., a PSA test, in which the levels of a protein in the blood are assessed) and digital rectal exam (DRE),
where the doctor feels for any enlarged, irregular, or firm areas on the prostate. Elevated PSA levels and/or an abnormal
DRE will usually prompt the doctor to perform a biopsy of the prostate. Typically during this procedure, a transrectal ultrasound
(TRUS) is used to visualize the prostate and help the physician guide the biopsy needle. A prostate biopsy is usually performed
in the doctor’s office with the patient under local anesthesia. The biopsy sample is then sent to a lab and assessed
by a pathologist, who specializes in diagnosing diseases by examining tissue, blood and body fluids. If cancer is present
in the biopsy sample, then further testing, such as a Computed Tomography (CT) scan, Magnetic Resonance Imaging (MRI), Positron
Emission Tomography-CT (PET-CT) scans, or bone scans may be recommended to determine the stage of cancer.
How is Prostate Cancer Treated?For
patients with early stage prostate cancer that is confined to the prostate itself, treatment options include surgery, external
beam radiation therapy (EBRT), brachytherapy (LDR and HDR), CyberKnife® Radiosurgery, hormonal therapy and watchful waiting.
Each of these options is explained in detail below. Prostate cancer surgery:
Prostate cancer
surgery involves complete removal of the prostate and some of the adjacent tissues (radical prostatectomy). There are two
types of surgery common for prostate cancer: open radical prostatectomy and laparoscopic prostatectomy. Open
radical prostatectomy:
There are two approaches to performing an open radical prostatectomy, a radical retropubic
approach and a radical perineal approach. During a radical retropubic prostatectomy, a long incision is made in the lower
abdomen and the surgeon removes the entire prostate with some surrounding tissues. Nerves in the surrounding tissues can be
easily damaged during this procedure, resulting in impotence, so surgeons often use techniques to preserve the nerves around
the prostate that control erections. Nerve-sparing techniques have been shown to decrease the incidence of impotence following
radical prostatectomy, but there is still a high risk of impotence following surgery. The radical perineal approach involves
the surgeon making an incision in the perineum, the skin between the testicles and the anus. Nerve-sparing techniques are
more difficult in this approach. Patients that undergo open radical prostatectomy typically spend three to four days in the
hospital and can expect to have a catheter remain in their urethra for three to four weeks to help with urination. Either
surgical approach poses a significant risk of possible complications for patients, such as infection, bleeding, lengthy hospital
stays, urinary side effects and impotence. In general, open prostatectomy is a highly effective modality for controlling prostate
cancer, with long-term (10-15 years) overall survival ranging from as high as 97%.2-5, 29 Urinary complications
are common shortly after surgery, and in the long term urinary incontinence may occur in 5-15% of patients and impotence has
been reported to occur in 50-80% of patients.6, 7 Laparoscopic prostatectomy:
Laparoscopic
prostatectomy is becoming more popular because it is less invasive. During this procedure, surgeons make several small incisions
in the abdomen. Instruments are inserted through the small incisions and are used to remove the prostate and surrounding tissues.
There is little evidence that laparoscopic prostatectomy is superior to open surgery in its ability to control the disease
but does have a reduction in complications.8, 9, 30, 31 Laparoscopic prostatectomy may be robotic-assisted; in
some reports of this method complications have been reduced relative to non-robotic prostatectomy (urinary incontinence has
been reported in 1-20% of patients, and impotence rates have ranged from 17-40%).10-14, 32 Patients who undergo
laparoscopic prostatectomy typically are hospitalized for two to three days with a catheter in place in the urethra and have
a shorter post-surgical recovery time compared to open surgery. External beam radiation therapy:
Radiation therapy is a non-invasive procedure that uses radiation to kill prostate cancer cells. Prior to treatment, CT
and MRI images are taken to determine the exact location of the prostate and surrounding structures. A treatment plan is then
created to deliver the radiation to the prostate and some of the surrounding tissue. It is necessary to irradiate some of
the surrounding healthy tissue during this treatment because there is a significant amount of variability in the day-to-day
location of the prostate and because the prostate can move inside the body from the effects of gas in the rectum and fluid
in the bladder, which cause uncertainties in the exact position of the prostate. Each treatment session lasts several minutes
and is painless. Treatments are typically delivered on an outpatient basis, five days a week, for 7 to 8 weeks.
Published outcomes of prostate cancer treatment by external beam radiation therapy include long-term survival of as high as
91%.4, 15-21 Patients may experience more rectal complications compared to surgery (10-20% of patients), urinary
toxicity has been reported in 10–15% of patients, and impotence has been reported in 20–64% of patients.6-8
Brachytherapy:
Brachytherapy is an invasive procedure that delivers radiation to the prostate
from a source that is implanted within the prostate. There are two approaches to brachytherapy treatments, low dose rate (LDR)
brachytherapy and high dose rate (HDR) brachytherapy. LDR brachytherapy:
In LDR brachytherapy,
small radioactive seeds about the size of a grain of rice are placed into the prostate and remain there permanently. Typically,
40 to 100 seeds are placed into the prostate through a needle, which is inserted through the skin. To relieve discomfort,
the procedure is done using spinal anesthesia or general anesthesia. The procedure may require overnight hospitalization.
The seeds emit low dose radiation to the prostate over several weeks or months, and the patient is radioactive while the radiation
is being emitted by the seeds. LDR brachytherapy results in a high rate of long-term survival, ranging from 85-94% in published
reports.4, 24, 25 Patients may experience low rates of urinary and rectal side effects (3-5%), and sexual dysfunction
has been reported in 20-50% of patients.8 In very rare situations, the seeds have become dislodged from the prostate,
enter the blood stream and migrate to other distant organs, but this does not typically pose health complications. HDR
brachytherapy:
HDR brachytherapy involves administration of high doses of radiation to the prostate over a
short period of time. Typically, an HDR brachytherapy procedure involves insertion of 12 to 20 hollow needles containing catheters,
which are inserted through the skin and into the prostate. Spinal anesthesia is usually given and the procedure often requires
overnight hospitalization. After the catheters are in place, a CT scan and/or MRI are taken to confirm the exact location
of the catheters, prostate and surrounding tissues. A treatment plan is then created and a radioactive source is placed through
the catheters to allow radiation to reach the prostate. The radioactive source remains at a location in the prostate for five
to 15 minutes and is then removed. Often the treatment occurs over several days and the catheters are removed after the last
treatment. Studies have shown that HDR brachytherapy results in excellent local control rates (89-98% in 3-6 years after treatment)
with rates of urinary, rectal and sexual function side effects that approximate those obtained with LDR brachytherapy.19-21
Nevertheless, this procedure can be painful and difficult for patients to undergo because of its invasiveness. Hormonal
therapy:
Male hormones, known as androgens, are produced normally by men and help support the growth of prostate
cancer cells. The goal of hormonal therapy is to decrease the amount of these specific hormones produced, in order to control
the growth of the prostate cancer cells. Hormonal therapy is usually prescribed in combination with other treatments, including
external beam radiation therapy, brachytherapy or before surgery to help shrink the size of the tumor. Side effects associated
with hormonal therapy can include decreased libido, impotence, hot flashes, osteoporosis and breast tenderness. HWatchful
waiting:
Prostate cancer is often a slow-growing cancer. Doctors may recommend that a patient receive no immediate
treatment, instead just closely monitoring the patient with PSA testing and rectal exams. Some men, especially those who are
older or have other health problems, may never need prostate cancer treatments. Radiosurgery:
Radiosurgery devices, such as the CyberKnife Robotic Radiosurgery System, offer patients a new option for the treatment
of prostate cancer. The challenge that doctors face in treating prostate tumors is that the prostate moves unpredictably as
air passes through the rectum and as the bladder empties and fills. Minimizing any large movements of the prostate can help
reduce unnecessary irradiation of surrounding healthy tissue. The CyberKnife System is able to overcome this challenge by
continuously identifying the exact location of the prostate tumor throughout the course of the treatment.
How Does The CyberKnife® Treat Prostate Cancer?The challenge that doctors face in treating prostate tumors
with radiation therapy is that the prostate moves unpredictably as air passes through the rectum and as the bladder empties
and fills. Minimizing any large movements of the prostate can help reduce unnecessary irradiation of surrounding healthy tissue.
The CyberKnife® Robotic Radiosurgery System is able to overcome this challenge by continuously identifying the
exact location of the prostate tumor throughout the course of the treatment. During CyberKnife treatment, a patient can lie
still and breathe normally while the doctor zeroes in on a moving target – the prostate – and irradiates it without
harming surrounding areas. As a result, the procedure is more comfortable for patients, radiation is delivered more accurately
and treatments can be completed in one to five days. Currently the CyberKnife Radiosurgery System is most frequently
used by itself for patients with early stage prostate cancer confined to the prostate or in combination with another therapy,
such as external beam radiation for patients with disease that extends beyond the prostate. In presentations at scientific
meetings and peer-reviewed publications, CyberKnife researchers have reported reliable reductions in PSA levels with low rates
of mild side effects during short-term follow-up after CyberKnife monotherapy.27, 28 Depending on the stage of
prostate cancer that is diagnosed, the doctor will recommend a treatment plan. What does a typical CyberKnife
treatment entail?
Prostate cancer treatment with the CyberKnife System involves a team approach, in which several
specialists participate. A team may include: - a Urologist
- a Radiation Oncologist
- a Medical Physicist
- Medical
Support Staff
Once the team is in place, the patient will begin preparations for CyberKnife treatment. As part
of their diagnosis, doctors will have measured prostate specific antigen (PSA) levels via a blood test that will be used to
help track treatment results. Prior to CyberKnife treatment, patients will be scheduled for a short outpatient procedure in
which three to five tiny gold seeds – called fiducial markers – are inserted into the prostate. The fiducials
are placed through a needle, which is guided via an ultrasound. Patients may be asked to clean out their rectum with an enema
the day of the fiducial placement. The CyberKnife System uses the fiducials as reference points to identify the exact
location of the prostate. Doctors will wait approximately one week after insertion of the fiducials before CyberKnife treatment
planning can begin to ensure that fiducial movement has stabilized. Prior to the treatment, a special custom-fit body
cradle will be made. The cradle is made of a soft material that molds to the patient’s body, ensuring that the patient
is in the same position for each treatment session and is comfortable during the procedure. While lying in the cradle,
patients will undergo a CT scan. This CT data will be used by the CyberKnife team to determine the exact size, shape and location
of the prostate. An MRI scan also may be necessary to fully visualize the prostate and nearby anatomy. Once the imaging is
done, the body cradle will be stored and used during CyberKnife treatment. A treatment plan will be specifically designed
by a medical physicist in conjunction with the patient’s doctors. Patients will not need to be present at this time.
During treatment planning, CT and/or MRI data will be downloaded into the CyberKnife System’s treatment planning software.
The medical team will determine the size of the area being targeted by radiation and the radiation dose, as well as identifying
critical structures – such as the bladder and rectum – where radiation should be minimized. At this time,
the CyberKnife System will be able to calculate the optimal radiation delivery plan to treat the prostate. Each patient’s
unique treatment plan will take full advantage of the CyberKnife System’s extreme maneuverability, allowing for a safe
and accurate prostate cancer treatment. After the treatment plan is developed, patients return to the CyberKnife center for
treatment. The treatment is usually delivered in one to five sessions. For most patients, the CyberKnife treatment is
a completely pain-free experience. They may dress comfortably in street clothes, and the CyberKnife center may allow patients
to bring music to listen to during the treatment. Patients also may want to bring something to read or listen to during any
waiting time, and have a friend or family member with them to provide support before and after treatment. When it is
time for treatment, patients will lie on their custom body cradle. The radiation therapist will ensure the body cradle is
properly adjusted and that patients are appropriately positioned on the treatment couch. When patients are ready for treatment
to begin, the location of the prostate will be tracked and detected. The medical team will be watching patients every step
of the way as the CyberKnife tracks the patient’s prostate as it moves, and safely and precisely delivering radiation
to it. The CyberKnife System’s computer-controlled robot will move around the patient’s body to various
locations from which it will deliver radiation. At each position, the robot will stop. Then, special software will determine
precisely where the radiation should be delivered. Nothing will be required of the patient during the treatment, except to
relax and lie as still as possible. Once prostate cancer treatment is complete, most patients quickly return to their
daily routines with little interruption to their normal activities. If treatment is being delivered in stages, patients will
need to return for additional treatments over the next several days as determined by their doctors. To date, prostate
cancer patients have experience only minimal short-term side effects from CyberKnife treatments. Data is still being collected
to evaluate long-term toxicity. Occasionally patients report temporary symptoms, which may include reduced urinary stream,
burning with urination, more frequent urination, increase in frequency of stools, loose stools and more gas with bowel movements
than usual. Doctors will discuss all possible side effects with their patients prior to treatment. In addition, doctors may
prescribe medication to control any side effects, should they occur. After completing a CyberKnife radiosurgery treatment,
it is important for patients to schedule and attend any follow-up appointments. Response to prostate cancer treatment varies
from patient to patient. Clinical experience today examining treatment outcomes up to 3 years following treatment, has shown
that most patients respond very well to CyberKnife treatments. CyberKnife physicians will monitor the outcome in the months
and years following a patient’s treatment using PSA tests and digital rectal exams.
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