External Beam Radiotherapy/ Intensity Modulated Radiotherapy (IMRT)
Q. What is external beam radiation?
A: External beam radiation involves the use of precisely focused photon radiation that is produced by a linear accelerator (treatment machine). External beam radiotherapy is the only completely non-invasive potentially curative treatment for Prostate Cancer. Radiation is invisible, tasteless and odorless. No radiation remains with the patient after each day of treatment. External beam radiation can be delivered alone (9 weeks) or in combination with seed implant (5 weeks). External beam radiotherapy is delivered Monday through Friday, 20 to 30 minutes per day/5 days a week for 5 weeks if given in combination with a seed implant or for 9 weeks if delivered alone.
What is IMRT?
A: IMRT is the type of external beam radiotherapy that we utilize for the treatment of prostate cancer and other malignancies. Allegheny General Hospital was one of the early pioneers of IMRT in the 1990’s. Utilizing IMRT, we are able to precisely shape the radiation fields to fit the shape and size of a prostate and avoid delivering dose of radiation to the nearby rectum or the bladder. IMRT involves both computerized treatment planning (using an inverse planning algorithm) and a computer driven treatment delivery system. IMRT involves taking each of the radiation beams and making it into smaller beamlets. Each of these beamlets can deliver a different dose of radiation to shape our fields however is necessary to obtain the best radiation dose distribution. The use of IMRT has been shown to significantly decrease side effects of radiation and allows us to deliver higher doses of radiation safely resulting in better cancer cure rates
What is image guided IMRT?
A: While IMRT allows us to precisely shape the radiation beams; Image guidance helps us focus the beams accurately on the prostate.
We have 2 methods of image guidance at Allegheny General Hospital; Cone Beam CT and Gold (Fiducial) Markers.
Cone Beam CT involves obtaining a specialized CT scan of the patient on the treatment couch each day at the time of treatment. The location of the prostate is visualized and compared to the location of the prostate on the treatment planning CT scan. The treatment couch is moved to account for changes in the location of the prostate assuring accurate set up. This technique allows us to visualize the prostate in three dimensions. The dose of radiation delivered from the CT scan is incorporated into the delivered dose of radiation so no additional dose is required for imaging. This is a procedure developed and uniquely applied by the staff at Allegheny General Hospital.
Another available technique for visualizing the prostate on a daily basis utilizes gold markers (fiducials). Three gold markers are placed in the prostate by the urologist. Placement of the gold markers is a procedure similar to a prostate biopsy. Each day prior to IMRT treatment, X-rays are obtained, the markers are seen on the X-rays and are aligned with the location of the markers on the planning CT. The location of these markers represents the location of the prostate. The treatment couch is moved to account for changes in the location of the prostate assuring accurate set up. Both of these techniques enable us to deliver high doses of radiation precisely to the prostate while sparing dose to the rectum, the bladder, the hip joints, and the small intestine.
What are the steps involved in receiving external beam radiation?
A: IMRT with image guidance is a three step process.
1) Simulation: involves a specialized CT scan of the pelvis performed on our dedicated CT scanner. This is usually done with Intra-venous (IV) contrast. The patient is positioned on their back on the treatment couch. A custom mold is made to help limit the external motion of the legs and torso. Ideally the patient will have an empty rectum and full bladder at the time of CT simulation (and treatment daily). After images are obtained, 3- 5 permanent marks (tattoos) are placed on the patient’s skin, these consist of pinpoint tattoos and these are utilized as preliminary set up points for daily treatment. After the CT simulation it may take a week before treatment is ready to start.
2) Treatment Planning; involves outlining the patients anatomy on the computer generated CT images. The radiation oncologist together with radiation physicists and dosimetrists will develop a computer generated plan that optimizes radiation dose delivery to the prostate and minimizes dose to the adjacent structures (bladder, rectum). This plan meets strict dose, quality assurance, and dosimetric guidelines. Once it is approved and once the quality assurance process is complete, the patient is called and daily treatments can begin.
3) Treatment; involves Monday through Friday 20-30 minute per day visit. The patient is placed on the treatment couch, the mold is fitted, and the image guidance images are obtained. Alignment is performed with table shifts and then the treatment is delivered. During treatment delivery the machine will rotate to five angles around the patient and will deliver radiation from each position. The treatment itself takes less than 15 minutes to complete.
What are the side effects from external beam radiotherapy?
A: External beam radiotherapy utilizing IMRT with image guidance is a non-invasive treatment modality, patients are able to maintain their daily lifestyles throughout the course of therapy. Patients are seen by the Radiation Oncologist and nurse at least once per week during treatment. In addition to the potential inconvenience of the daily treatment, some patients may develop bladder irritation resulting in both daytime and nighttime urinary frequency, possibly burning with urination. These symptoms can develop during the course of radiotherapy and can last for one to two months after the completion of radiotherapy. Typically medications such as Flomax (or Uroxatral) are very successful in relieving these symptoms. During the course of treatment, some patients may develop rectal irritation, sometimes diarrhea and rarely rectal bleeding. These side effects are usually self limited or treated with modifications in diet or with over the counter medications. Long term effects on the bladder and rectum are uncommon after external beam radiotherapy using IMRT with image guidance, however, there are occasional cases rectal bleeding and bleeding from the bladder which can occur months to years after treatment. Scar tissue formation affecting the bladder or ureters is a rare side effect as well.
What if external beam radiotherapy is not successful?
A: If external beam radiotherapy does not cure a patient’s prostate cancer, there are other options for treatment. It is important first to determine whether the patient’s prostate cancer recurred because of recurrence in the prostate or because of spread of cancer elsewhere in the body. If after a thorough work-up it is determined that there is persistence or recurrence in the prostate, then patients may be a candidate for cryosurgery or for androgen deprivation therapy. If the disease is spread elsewhere in the body, then androgen deprivation therapy alone would be indicated. Patients are typically not candidates for prostatectomy (or surgical removal of the prostate) after radiation treatment due to changes in the tissues which make surgery difficult.
How successful is external beam radiotherapy?
A: There are numerous studies looking at the outcomes for patients treated with external beam radiotherapy. External beam radiotherapy using IMRT with image guidance is a very effective way of treating prostate cancer. Studies have shown that the results are similar to those of seed implant or prostatectomy for ideal candidates.
Q: Can you summarize the pros and cons of external beam radiotherapy?
A: The cons of external beam radiotherapy are potential inconvenience for patients, the risk of short term urinary and bowel symptoms including diarrhea and a risk of developing long term bowel and bladder complications.
The pros of External beam radiotherapy with IMRT and image guidance are that it is an entirely non-invasive treatment and the results are comparable to other invasive treatments for prostate cancer. There are no requirements relative to prostate size, previous surgeries, and external beam radiotherapy can be safely delivered to patients not healthy enough to undergo surgical procedures. There is no radiation exposure to others from external radiation
Q: What is a prostate seed implant (Prostate Brachytherapy)?
A: Prostate seed implant is a potentially curative treatment for prostate cancer (and other malignancies) where radioactive seeds (smaller than the size of a grain of rice) are inserted into the prostate through hollow needles. The radioactive seeds give off radiation over a period of time which irritate the normal cells and kill the prostate cancer cells.
Q: Is prostate seed implant a new procedure?
A: Implanting radioactive sources has been done for well over 100 years. The technique that we utilize to implant radioactive Iodine 125 or Palladium 103 seeds has been utilized for approximately 20 years. The advent of this technique coincided with the use of rectal ultrasound technology. We now utilize sophisticated ultrasound visualization of the prostate and real-time intra-operative computer driven treatment planning to optimize the dose delivery to the prostate.
Q: Who is a candidate for seed implantation?
A: Seed implantation alone or in combination with external beam radiotherapy can be utilized for most patients with early or intermediate risk prostate cancer. Typically patients who have significant urinary symptoms ( such as frequency, difficulty starting a stream) or those who have an enlarged prostate (>60cc) are not good candidates for seed implant. Patients who have had prior procedures such as TURP may not be ideal candidates for prostate seed implant depending on the size of the surgical defect from TURP.
Q: Why do some patients need IMRT and seed implant?
Some prostate cancer can spread outside the confines of the prostate. Patients who have a PSA over 10, a Gleason score of 7 or higher, and/or a large mass on exam have a higher risk of cancer outside the prostate. For these patients a seed implant alone does not treat enough area outside the prostate and these patients may benefit from a five week course of IMRT before the seed implant. Sometimes the IMRT can be done at a facility closer to where the patient lives. Seed implant is usually done 2-4 weeks after completion of IMRT
Q: How is seed implant performed?
A: 1) The first step for a patient undergoing a prostate seed implant is to undergo a volume measurement of the prostate. This is a several minute outpatient procedure done by our urologist. An ultrasound probe is placed in the rectum and a measurement of the size of the prostate is obtained. This step is needed for us to know how many seeds to order
2) Once a date and time for the procedure are arranged with the Urologist and Radiation Oncologist, the patient is given oral antibiotics and will undergo any pre-operative tests and/or medical clearance from their doctor for the procedure.
3) On the day of the procedure the patient is admitted to a room in the outpatient surgery center, on the 11th floor of the hospital. When the Operating room is ready the patient will be brought down to the pre-operative holding area. The anesthesiologist and the urologist will speak with the patient. The patient will then go to the operating room and an anesthetic will be administered. Typically patients will have a general anesthetic, but a spinal anesthetic is sometimes used.
4) The procedure to place the seeds takes up to an hour to complete. Seeds are placed into the prostate through hollow needles implanted through the skin between the legs. 60 – 100 seeds are implanted depending on the shape and size of the prostate. A computerized, real time plan to determine ideal seed placement is utilized in the operating room. The procedure is performed by the urologist and radiation oncologist as well as an experienced support staff. After the procedure, the patient goes to the recovery room for an hour or two and is then returned to their room in the outpatient surgery center. The patient typically will have a catheter in their bladder.
5) When the patient is stable for discharge, their catheter will be removed and they can be discharged. If they cannot start a stream of urine, the catheter will be re-inserted and the patient will be discharged with a catheter. The catheter will then be removed in a couple of days.
6) A CT scan of the pelvis to verify seed positioning will be done one month after the implant is performed. This CT needs to be done at AGH.
Q: What are the side effects from seed implant?
- About one out of ten patients will go home from the hospital with a catheter.
- Most patients will see blood in their urine for two weeks or so after the procedure, this will resolve on its own
- Starting one to two weeks after the procedure, patients commonly experience urinary frequency, the need to get up more often at night, burning with urination, and sometimes urgency. These symptoms can sometimes last up to a year. We treat these symptoms with medications such as Flomax or Uroxatral which may need to be continued for up to a year after the implant.
- Rectal irritation and rarely bleeding can occur up to one year after the implant
- Erectile dysfunction can occur after implant. One study showed a rate of 15% impotence at 2 years and 35% rate at 6 years after implant. Medications (Viagra. Levitra, Cialis) can sometimes help relieve these symptoms. Other treatments are also available.
- Dry ejaculate sometimes can occur after implant
- Bleeding from the bladder is a possible but rare long term side effect.
Q: What happens to the seeds:
The metallic seeds stay in the patient forever. The radioactivity decays and becomes undetectable over several months.
Q: What are the precautions for radiation safety?
After the seed implant there is radioactivity inside the patient. The NRC states that such patients do not present a risk to the people around them, including young children and pregnant women. However, in keeping with the general principle that radiation exposure should be kept as low as reasonably possible, we suggest the following:
1) Both Palladium-103 and Iodine-125 are low-energy radioactive materials. They are not deeply penetrating and lose their energy at a short distance. Almost the entire dose is contained in the prostate gland. Tiny and probably trivial amounts of the radiation may nevertheless be detected beyond the body.
2) Objects that are touched or used by you do not become radioactive. Body wastes (urine and stool) or body fluids (saliva, tears, semen, or blood) are not radioactive.
3) Children should not sit on the patient’s lap for the first three months after the implant.
4) Pregnant (or possibly pregnant) women should avoid prolonged, close contact with the patient for the first three months after the implant.
5) At a distance of several feet, there is no limit to the length of time anyone can be with the patient.
6) For the first 2 months, use a condom when engaging in sexual intercourse, in the very rare event that there is a radioactive seed in the semen.
After the first three months, no further radiation precautions are necessary
In the rare case that you find a seed:
Under no circumstances should you handle a seed with your fingers. Use a spoon or tweezers to place it in the toilet and flush twice
If you do find a seed do not keep it for any reason
Q: What happens to the Prostate Cancer and PSA after the seed implant?
We usually do not recommend checking a PSA ( blood test) for three months after an implant. Some doctors do not check a PSA for six months. This is because the PSA can bounce up and down and can cause unnecessary concern for patients soon after the implant. Typically PSA will be checked every three to six months for the first several years after implant and then every year. We expect the PSA to decline under 1.0 and to stay there forever. You will be seen every six months by a urologist or radiation oncologist for the first several years after implant.
Q: How successful is seed implant?
Seed implant, IMRT, surgery all have very similar cure rates for prostate cancer. One study which followed 3000 patients with early stage prostate cancer for 8 years showed a 93% PSA control rate for patients with early stage and low grade prostate cancer.. Studies of the results for patients with early stage prostate cancer treated at AGH over the past five years show a PSA control rate of 94%.
Q: What if seed implant or IMRT is not successful?
Due to changes in the anatomy around the prostate, surgery cannot typically be done after seed implant or IMRT. If prostate cancer recurs these patients are typically treated with androgen deprivation (medications that block testosterone) or with cryosurgery (freezing of the prostate).
Q: Are these treatments covered by insurance?
IMRT with image guidance and seed implants are covered by medicare and by most insurance carriers.