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Radiation therapy has been used to treat prostate cancer for more than 100 years. During the past 20 years, tremendous advances in technology have revolutionized radiation therapy, making it an even more effective and safe option for the treatment of prostate cancer.
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How Radiation Therapy Works to Eradicate Cancer Cells?
Types of Radiation Therapy
The Role of Hormone Therapy With Radiation Therapy
Which Type of Radiation Therapy is Most Appropriate?
More About IMRT
Treatment
More About Brachytherapy - permanent seed implantation
Potential Side Effects of Radiation Therapy
Temporary Short-Term Effects
Potential Long-Term Side Effects
Potential Long-Term Sexual Side Effects
Potential Long-Term Bowel Side Effects
Second Cancer
Follow Up
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How Radiation Therapy Works to Eradicate Cancer Cells?
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Prostate cancer is a disease in which abnormal prostate cells grow and reproduce uncontrollably. Radiation therapy works by damaging the DNA within cancer cells and destroying their ability to reproduce. Relative to normal cells, cancer cells are more susceptible to radiation therapy because of their constant growth and limited ability to repair radiation damage.
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Types of Radiation Therapy
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There are 3 methods of radiation therapy used to treat prostate cancer.
1. External beam radiation therapy: Radiation beams are generated in a treatment machine external to the patient and sophisticated computers are used to target the radiation beams at the prostate. The most common type of radiation used is high energy x-rays (also known as photons). Other less common types of radiation used are protons and neutrons.
There are 2 principal methods of delivering external beam radiation therapy:
3-dimensional conformal radiation therapy: CT scans are used to obtain 3-dimensional information about a patient's cancer and normal anatomy. A 3-dimensional model of the patient's anatomy is reconstructed on a computer, and a treatment plan is designed to focus multiple radiation beams at the patient's prostate. The dose of radiation is shaped to conform to (match the shape of) the patient's prostate and anatomy, maximizing radiation to the cancer while minimizing the dose to surrounding normal tissues.
Intensity modulated radiation therapy (IMRT): IMRT, the most recent advance in external beam radiation therapy, greatly improves upon 3-dimensional radiation therapy. Enhancements in the treatment machine and computer planning software allow each radiation beam to be divided into hundreds of smaller beams (called beamlets). The intensity of each of these beamlets may be modulated, allowing a finer adjustment of the radiation doses, and significantly improving the focus of the radiation on the cancer. An integral part of IMRT is the use of sophisticated treatment planning computers to optimize the many treatment variables (including the thousands of beamlets and their variable intensities). The result is higher doses of radiation to the cancer and lower doses to the surrounding normal tissues, translating into a greater chance of cure and a lower risk of side effects. At the Marin Cancer Institute, IMRT is utilized for prostate cancer therapy.
2. Brachytherapy (also known as radioactive seed implantation): Radiation is delivered directly to the cancer by inserting radioactive seeds into the prostate.
There are 2 methods of brachytherapy:
Permanent seed implantation: Under anesthesia, small radioactive seeds (or pellets) are implanted into the prostate by passing the seeds through hollow needles inserted into the prostate. The seeds are placed permanently in the prostate. The radioactivity released from the seeds travels only a short distance, delivering a high dose of radiation to the prostate, while limiting the dose of radiation to the surrounding tissues. The seeds eventually lose their radioactivity, losing most of their radioactivity within 2 to 6 months, depending on the type of seeds used. The 2 most common types of seeds used are Iodine-125 and Palladium-103.
Temporary seed implantation (also known as High Dose Rate or HDR): Catheters (tubes) are implanted into the prostate. The catheters pass out of the body and are connected to a machine, which passes a high dose radioactive seed through the catheter and into the prostate for short periods of time (minutes). The treatment is called high dose rate because a high dose of radiation is given in the short time that the seeds are placed in the prostate. The catheters are left in the prostate for 1 to 2 days and the seeds are passed in and out of the prostate 2 to 3 times during this period. The whole procedure is repeated again in one week. HDR is typically used in conjunction with external beam radiation therapy for more advanced cancers (see next section). There is less long-term experience with HDR as a stand-alone treatment for early stage prostate cancers.
3. Combined external radiation therapy and brachytherapy: Both external beam radiation therapy and brachytherapy (permanent seed or HDR) may be combined for more advanced or aggressive cancers. The brachytherapy delivers a high dose of radiation directly to the prostate while the external beam radiation therapy delivers radiation to the surrounding tissues where the cancer may have spread. The amount of each type of treatment (external beam radiation and brachytherapy) are decreased when combined. Treatment starts with 5 weeks of external radiation therapy followed 2 to 4 weeks later by the brachytherapy procedure.
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The Role of Hormone Therapy With Radiation Therapy
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In certain situations, a course of hormone therapy may be recommended along with radiation therapy. Hormone therapy reduces the level of the male hormone testosterone in the body. Prostate cells require testosterone to remain active. By reducing the level of testosterone in the body, the prostate cancer cells shrink and become inactive. Hormone therapy is usually given in the form of a slow release medication (a single injection of the medication may last 1 to 4 months, depending on the dose).
Hormone therapy is used in conjunction with radiation therapy for 2 primary functions:
Hormone therapy can be used for 2 to 3 months prior to radiation therapy to shrink the size of a large prostate. This is occasionally used prior to brachytherapy (discussed later).
For more advanced or aggressive cancers, hormone therapy works together with radiation therapy to improve the effectiveness of the radiation therapy. Hormone therapy is started 2-3 months before radiation therapy and continued through the course of radiation therapy. For some of these cancers, hormone therapy may be continued after radiation therapy for a total of 2 years.
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Which Type of Radiation Therapy is Most Appropriate?
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The choice of treatment depends on the characteristics of the cancer and the patient's urinary function, general health, age, and personal preferences.
Radiation Treatment Options by Prostate Cancer Risk GroupProstate Cancer Risk Group | IMRT | Brachytherapy | Combined IMRT
+ Brachytherapy | Adjunctive
Hormonal Therapy | Low | Yes | Yes | No | No (unless to shrink the prostate) | Intermediate | Yes | Selected Cases | Yes | Sometimes
(4 to 6 months) | High | Yes | No | Yes | Yes
(2 years) |
Contraindications to brachytherapy
Brachytherapy is generally not recommended when a patient has significant urinary symptoms (such as straining to urinate, weak urinary stream, waking up frequently at night to urinate), undergone a prior TURP (transurethral resection of prostate) procedure, or a very large prostate. For patients with borderline enlargement of their prostate, hormonal therapy may be used prior to brachytherapy to reduce the size of their prostate.
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More About IMRT
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IMRT is a non-invasive procedure, which requires no hospitalization or anesthesia. The treatments themselves are painless (similar to undergoing a chest x-ray for example). Patients are able to drive themselves to and from their treatments. Patients do not become radioactive.
IMRT involves a series of daily treatments, 5 days per week, given over 8 weeks. Although the actual time of the radiation delivery is short, patients typically spend 20-30 minutes per day in the treatment center.
Radiation therapy may be aimed at just the prostate or to the surrounding tissues and pelvic lymph nodes as well. One advantage of radiation therapy for higher risk cancers is the ability to treat areas outside of the prostate to which the cancer could potentially spread. The extent of treatment depends on the risk of spread, which is determined by each individual patient's prostate cancer characteristics. These characteristics place his cancer into a prostate cancer risk group. For patients with prostate cancers in the low risk group, treatment is limited to the prostate, since the risk of spread to the surrounding tissues is low. For patients with prostate cancers in the high-risk group, the risk of spread becomes significant and treatment is directed to the prostate and pelvic lymph nodes. IMRT is particularly advantageous for treatment of the lymph nodes since it can greatly reduce the doses to the surrounding normal tissues in the pelvis. The precision of radiation therapy is greatly enhanced with the use of guidance systems to target the prostate. The position of the prostate can shift between treatments, and these guidance systems track the position of the prostate at the time of each treatment. One technique is the use of x-rays to locate marker seeds placed in the prostate. Another technique is the use of ultrasound to visualize the prostate (also known as BAT). These techniques are known as Image Guided Radiation Therapy (IGRT). Images (x-rays or ultrasound) are used to precisely guide the radiation therapy. The Marin Cancer Institute has both marker seed and ultrasound (BAT) technologies.
Preliminary Steps to Starting IMRT
1. Hormonal therapy: If hormone therapy is used, it is initiated by the patient's urologist 2-3 months before the start of radiation therapy. For very large prostates or more advanced cancers, up to 6 months of hormone therapy may be used. The cancer is being actively treated by the hormone therapy during this period.
 CT Scan |  MRI |
2. Prostate gold seed marker placement: Three small gold seed markers are implanted into the prostate and used to target the prostate prior to each daily radiation treatment. The procedure is similar to a prostate biopsy and performed by a urologist at least 1 week prior to simulation (next step).
3. Simulation: During simulation, measurements and x-rays are taken to set-up the treatment. A custom body mold is made to maintain consistent positioning for every treatment.
4. CT scan: A CT scan is used to obtain 3-dimensional information about the patient's anatomy.
5. MRI scan: A MRI scan is used to supplement the CT scan with more detailed anatomic information. The prostate, rectum, and bladder are much more clearly identified with a MRI scan. The use of a MRI for treatment planning is relatively unique to the Marin Cancer Institute.
6. Treatment planning: Treatment planning is performed by a team composed of a physician, PhD physicist, certified dosimetrists, and licensed radiation technologists. Our physicians have an integral hands-on role in the process. Sophisticated computers use the information from the simulation, CT scan, and MRI scan to reconstruct a 3-dimensional model of the patient's anatomy and devise a plan of treatment. An essential part of IMRT is Inverse Treatment Planning, a process in which a very advanced computer's processing power is harnessed to search for the best possible treatment plan given a desired idealized goal. The computer will test all potential treatment plans and present the best solution. A number of quality assurance testing measures are performed prior to initiating treatment. This whole process typically takes 1- 2 weeks.
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Treatment
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Daily treatments are performed by specially trained and licensed radiation technologists (RT). Precise treatment is ensured by the use of the gold seed markers to target the prostate prior to each daily treatment. X-rays are taken each day to adjust and verify the accuracy of treatment. The x-rays are reviewed by the physician each day. During the course of treatment, the patient's physician sees him each week to monitor the progress of therapy. Each patient is monitored by a certified oncology nurse (OCN) each week as well.
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More About Brachytherapy - permanent seed implantation
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 Seeds compared to a dime. |  X-ray of seeds in a patient. | Brachytherapy is performed in 2 steps:
1. Prostate volume study: An ultrasound is performed to map out the size (volume) and shape of the prostate. This information is captured electronically and a treatment planning computer is used to reconstruct a 3-dimensional model of the prostate. The number, position, and dosage of seeds required to treat the prostate cancer is calculated and a plan of treatment is developed. The radioactive seeds are custom ordered for each patient.
2. Seed implantation: Brachytherapy is a minimally invasive treatment. Seed placement is performed in the hospital as an outpatient procedure, which typically takes a couple of hours. The procedure is performed under general or spinal anesthesia. Hollow needles are placed into the prostate through the perineum (area between the scrotum and anus). The seeds are placed into the prostate and the needles are removed. No incisions are made, and there is minimal blood loss. Ultrasound imaging and a special template guidance system ensure accurate placement of the seeds into the prostate. The radiation released by the seeds travels a limited distance and most of the radiation is absorbed within the prostate. The seeds lose their radioactivity over time (exponentially). The need for a urinary catheter is uncommon. The procedure is usually performed in the morning and patients typically go home after eating lunch.
Two types of radioactive seeds are commonly used:
- The Iodine-125 seeds have a half-life of 2 months. That means that half of the radiation activity is lost every 2 months. In the first 2 months, the activity decreases from 100% to 50%. Between months 2 and 4, the activity decreases from 50% to 25%, and so on.
- The Palladium-103 seeds have a half-life of 17 days.
More About Combined IMRT and Brachytherapy:
When IMRT and brachytherapy are combined, IMRT is performed first for 5 weeks. The brachytherapy is performed approximately 1 month following the completion of IMRT.
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Potential Side Effects of Radiation Therapy
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The side effects of modern radiation therapy are significantly less than treatments performed even 5-10 years ago. Side effects may be divided into temporary short-term side effects and potential long-term side effects. A more detailed review of potential side effects will be discussed by your physician.
Side Effects That Do Not Happen
There is no hair loss, nausea/vomiting, or skin burns associated with prostate cancer IMRT or brachytherapy.
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Temporary Short-Term Effects
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In general, treatment is well tolerated. The degree of side effects depends on whether treatment is limited to the prostate only or includes the pelvic lymph nodes. Some patients with higher risk cancers undergoing more aggressive treatment to the prostate and pelvic lymph nodes may experience more side effects.
Fatigue: Patients may temporarily experience varying degrees of fatigue. This side effect is usually mild to moderate and does not typically interfere with a patient's normal daily activities. Some patients feel fine and work a full day, while others may require more rest. Patients are encouraged to remain active, since patients who remain physically active typically experience less fatigue.
Urinary side effects: Patients may temporarily experience changes in their urinary habits. Symptoms may include more frequent urination, urgency, a slower urinary stream, and irritation or burning. These side effects are typically minimal to moderate. Occasionally, a few patients may experience more intense or longer lasting symptoms. This is particularly true for patients undergoing treatment to the pelvic lymph nodes. If necessary, there are medications that can treat these symptoms.
Bowel side effects: Patients may temporarily experience changes in their bowel habits. Symptoms may include more frequent bowel movements, urgency, and soft or loose stools. These symptoms are typically less common than the urinary symptoms and are generally minimal to mild. Changes in diet or over-the-counter medications can treat these symptoms if necessary. These symptoms may be more significant for patients undergoing treatment to the pelvic lymph nodes and/or patients with underlying bowel problems such as inflammatory bowel disease.
Additional side effects unique to brachytherapy: Immediately following the implant procedure, patients may experience symptoms related to the implantation procedure (rather than the radiation). These may include bruising between the legs, blood in the urine, and uncommonly, the need for a catheter.
Hormone therapy related side effects: Please refer to the chapter on hormone therapy.
External beam radiation therapy: External beam radiation treatments (like chest x-rays for example) do not cause the patient to become radioactive. No special radiation safety precautions need to be taken.
Brachytherapy (permanent seed implantation): The radioactive seeds within the patient's body are temporarily radioactive. However, the radiation does not make any part of the patient's body or any of his bodily fluids radioactive. The radiation released by the seeds travels a limited distance and most of the radiation is absorbed within the prostate. A very small amount of radiation escapes the body. No special precautions are required for spouses. One study measured the dose of radiation received by spouses during a one-year period. The exposure was equivalent to taking a round-trip airline flight between New York and Tokyo. (At high altitudes, people are exposed to higher doses of cosmic x-rays.) Special precautions are recommended for pregnant (or possibly pregnant) women and growing children. Pregnant women should keep a distance of 6 feet from the patient and children should not sit on the patient's lap for the first 2 months following an Iodine implant and the first 3 weeks following a Palladium implant. (The time differences are due to the different lengths of radioactivity of these 2 elements).
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Potential Long-Term Side Effects
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Generally, men regain the same urinary function they had prior to radiation therapy.
Incontinence: The risk of long-term urinary incontinence following radiation therapy is very low since the prostate is not removed.
Stricture: There is a low risk of developing scar tissue in the prostate region. This scar tissue may narrow the urethra and weaken the flow of urine. This may require a urethral dilation (stretching) or other procedure to relieve the obstruction. Following radiation therapy, patients should consult with their radiation oncologist prior to undergoing any invasive urinary procedure.
Changes in urinary habits: A small percentage of men may develop a more sensitive prostate and bladder (more urinary frequency, urgency, or a weaker stream).
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Potential Long-Term Sexual Side Effects
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Impotence: Approximately 20-50% of men may develop difficulty achieving or maintaining an erection starting 6-12 months after radiation therapy. The risk is dependent on a patient's age, baseline sexual function, and other health conditions. Younger men with good sexual function prior to treatment and no other risk factors for erectile dysfunction (such as arteriosclerosis, high blood pressure, diabetes, and smoking) have a lower risk of developing erectile dysfunction. Conversely, older men with pre-existing erectile difficulties and other health problems will have a higher risk. Medications such as Viagara, Cialis, and Levitra are generally effective. If not successful, other treatments such as vacuum pumps or injection therapy may be recommended.
Decreased ejaculate: The sperm are produced in the testicles. The prostate and seminal vesicles produce a fluid (making up the majority of the ejaculate), which aids the sperm to fertilize an egg. Most men will have a permanent decrease in the amount of ejaculate with climax. This does not affect the ability to achieve a climax.
Decreased fertility: The change in the ejaculate generally results in decreased fertility. If a patient is interested in fathering children after treatment, sperm banking is recommended. Conversely, some men may still be fertile following treatment and appropriate contraception should be used as necessary. There is a remote possibility that radiation may temporarily affect the sperm. Therefore, men should wait 18 months before fathering children.
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Potential Long-Term Bowel Side Effects
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Rectal bleeding: Some patients may have an aggravation of their hemorrhoids or develop radiation proctitis (superficial irritation of the rectum immediately adjacent to the prostate). This may result in painless bleeding seen intermittently on the toilet tissue or with the stools. Typically, the amount of blood is insignificant and the bleeding eventually stops on its own. Patients on blood thinners have a higher risk of rectal bleeding. Suppository medications may be recommended. With modern radiation therapy techniques, this occurs less frequently and is seen in less than 10% of patients. A few percent of patients may require a minor procedure to treat the bleeding.
Rectal ulcer: This is a very rare complication that may require surgery to fix or bypass the damage. This may be aggravated by a biopsy or other invasive rectal procedures. Following radiation therapy, patients should consult with their radiation oncologist prior to undergoing any invasive rectal procedure.
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Second Cancer
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Prostate cancer survivors are not at higher risk of developing other cancers compared to the general population. Patients treated with radiation therapy are at a slightly higher risk of developing a second cancer in the irradiated area (such as the bladder or rectum). The risk of a second cancer is very rare. If a second cancer occurs, it typically occurs many years after treatment.
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Follow Up
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Frequency of follow-up visits: Patients who undergo external beam radiation therapy are seen 1 month after the completion of treatment and then every 6 months. Patients who undergo brachytherapy are seen at 1 week, 1 month, 3 months, and 6 months after the implant (the period of time when the majority of radiation is released from the seeds). They are then seen every 6 months. Follow-up visits usually alternate between their radiation oncologist and their urologist.
PSA testing and PSA response: The goal of curative treatment is eradication of the cancer, with prevention of cancer related symptoms and death. Following any treatment, PSA is used to monitor cancer activity. The PSA is generally checked every 6 months. After radiation therapy, the PSA should decline to a low level (generally less than 1.0 ng/ml) and remain low indefinitely. A steadily rising PSA is an early sign of recurrent cancer.
PSA bounce: Following brachytherapy, the PSA may temporarily rise and then decline during the first couple of years. This may be due to prostate cells dying and releasing their PSA or it may be the result of inflammation or infection. If this occurs, the PSA is rechecked in 2 months.
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