Radiation therapy involves exposing the prostate and, depending on the type of radiation used, also the surrounding areas to x-rays or other types of radiation designed to destroy cancer cells or at least prevent them from growing and spreading. The two types of radiation therapy used to treat prostate cancer are external beam radiation therapy (EBRT) and an associated EBRT called conformal EBRT (a subtype of which is proton therapy); and brachytherapy.
External beam radiation therapy, or EBRT, involves exposing the prostate gland and surrounding tissues to radiation doses, given daily in separate individual treatments. The radiation is delivered in this way because cancer cells are sensitive to radiation at different stages in their growth. When the cancer cells are exposed to radiation every day for a designated treatment period (typically five days a week for 6 to 7 weeks), there is a better chance of catching the cancer cells when they are most sensitive and also not allowing them to recover from radiation damage.
A more precise type of EBRT is conformal EBRT, in which the radiation oncologist uses CT images to help him or her better see where to treat the prostate gland. The three-dimensional images also allow the radiation oncologist to identify surrounding structures, such as the bladder and rectum, and to deliver a higher amount of radiation to the prostate while minimizing the radiation to surrounding normal tissue. A new subtype of conformal EBRT is also available in some markets called proton therapy that is a type of conformal radiation therapy that delivers high doses of protons to a targeted area. More on proton therapy
The ideal candidates for both types of EBRT are men who have a life expectancy of 7 to 10 years. In men who have higher risk prostate cancer, the increased radiation delivered via conformal EBRT can lead to a better decrease in PSA progression than the dose used in conventional EBRT. Hormonal therapy is often prescribed along with EBRT for men who have a Gleason score of 7 or higher or a PSA of 10 ng/mL or higher.
Overall, the amount of radiation delivered and the area treated differs for each individual and depends on the stage and Gleason grade. Men who have a history of inflammatory bowel disease or a history of previous pelvic radiotherapy are not good candidates for radiation.
The success rates for both EBRT and conformal EBRT depend on the initial PSA level. Studies show that 89 to 92 percent of men who underwent conformal EBRT who had a pretreatment PSA of less than 10 ng/mL had no increase in their PSA level at five years. Those who had a pretreatment PSA of 10 to 19.9 ng/mL had an 82 to 86 percent chance of having no increase in PSA level at five years, while those with a PSA greater than 20 ng/mL showed a 26 to 63 percent chance of having no increase in PSA at five years.
Both types of EBRT can cause side effects that occur within 90 days after receiving radiation treatment (acute side effects) or more than 90 days after radiation treatment (late side effects). The severity of the side effects varies and depends on the type and length of treatment, treatment site, and the individual patient’s tolerance for radiation.
The most common acute side effects include:
- Changes in bowel habits, such as development of diarrhea, abdominal cramping, rectal pain, rectal bleeding, and feeling the need to have a bowel movement
- Skin irritation, with the most sensitive areas being the perineum and the fold under the buttocks
- Edema, which may affect the legs, scrotum, or penis. This side effect is rare.
- Rectal and urinary irritation, although the effects from conformal EBRT are typically less severe
- Urinary symptoms such as urinary urgency, hesitancy, and increased urination during the night.
Late side effects can include persistent bowel problems, persistent urinary symptoms, urinary bleeding, erectile dysfunction, and urethral stricture.
The Calypso ® 4D Localization System™ is a type of external beam radiation that has been called the GPS for the Body. For men who choose the Calypso System, tiny electromagnetic transponders (“seeds”) are permanently implanted into the prostate during an outpatient procedure before radiation therapy is initiated. These transponders send out radiofrequency signals which are detected by the Calypso System and the 4D Tracking Station. Because the prostate can move during radiation due to normal breathing and movement of the intestinal tract, these signals allow physicians to see exactly where the tumor is at all times during radiation treatment. Thus they can pinpoint the treatment area and avoid radiating nearby healthy tissues, sparing the colon, bladder, and other important structures, and minimizing side effects of radiation such as urinary incontinence and erectile dysfunction. Calypso has been approved by the Food and Drug Administration (FDA) for treatment of prostate cancer, and holds promise of treating other cancers in the future. (University of Maryland)
Brachytherapy involves implanting either permanent, tiny, radioactive capsules (“seeds”) or temporary needles into the cancerous prostate gland. The physician can use either a transrectal ultrasound or a CT scan to evaluate the prostate and help in the placement of the seeds or needles. The seeds send out a radioactive agent—either palladium 103 or iodine 125–over weeks or months to kill the tumor. Men who have small tumors that are confined to the prostate are candidates for this approach. Palladium provides a higher initial dose of radiation and is usually used for tumors with a Gleason score of at least 7, while iodine is used to treat tumors with a Gleason score of 6 or lower.
Placement of the seeds is a minimally invasive procedure and does not require any incisions. Men who undergo seed implantation can typically return to full activity within 3 to 4 days after the procedure. For men who are at high risk for cancer spreading outside the prostate, their oncologist or urologist may recommend that they undergo EBRT along with seed implantation.
The temporary brachytherapy method involves placing needles (also referred to as catheters) into the prostate, and giving the radiation through the needles. A computer-controlled machine is used to supply the radioactive iridium seed into the needles and also controls how long each seed remains in there. Therefore this method allows a radiation oncologist to change the dose after the needles are placed which is an advantage over permanent seed placement.
Brachytherapy is associated with a variety of common side effects. Men who receive palladium typically experience urinary symptoms earlier because it releases high energy sooner than iodine. Side effects that can affect men who undergo brachytherapy include:
- Urinary symptoms such as urinary retention, frequent urination
- Bladder outlet obstruction, which results in difficulty or an inability to urinate, occurs in 7 to 25 percent of men
- Urinary incontinence occurs in less than 1 percent of men
- Rectal ulceration and bleeding, which is seen in less than 5 percent of patients
- Urethral stricture, or narrowing of the urethra, is related to the formation of scar tissue. It occurs in 5 to 12 percent of men and tends to develop later
- Erectile dysfunction may occur in as many as 40 to 60 percent of men who undergo brachytherapy
- A temporary and benign increase in PSA levels occurs in some men
The ideal candidate for brachytherapy is a man whose life expectancy is more than 7 to 10 years, who has localized prostate cancer of low to intermediate risk, and who has no underlying illness that would complicate the procedure.
Information about the long-term success rates of brachytherapy is limited and complicated by the fact that most men in the studies have had more than one additional treatment for prostate cancer. Success is usually defined as a PSA of less than 0.5 ng/mL. Generally, 10-year success rates of 64 to 85 percent have been reported.
A form of external beam radiation therapy that is more advanced than traditional radiation treatments is a subtype of conformal radiation called proton therapy, which until recently has been available only at research facilities. Proton therapy is a type of conformal radiation therapy that delivers high doses of protons to a targeted area, which radiation oncologists can achieve using advanced imaging techniques that allow them to identify the exact location of the tumor.
Protons cause less damage to healthy tissues than does conventional radiation therapy because once the energy has reached the tumor, there is no exit dose. In conventional radiation, the x-rays continue past the treatment site, causing additional damage to tissues as they go. Therefore with proton therapy, healthy tissue receives less exposure to radiation, leading to fewer complications and a greater probability of success. Proton therapy for prostate cancer typically takes place for five days a week for eight weeks.
Proton therapy, which has been studied and used successfully for the past seven years at the Loma Linda University Proton Treatment Center in Southern California, offers men with prostate cancer a new way to treat the disease. In addition to the ability to focus more accurately on the cancer, proton therapy has also been associated with a very low rate of cancer recurrence within the prostate treatment field. Dr. Slater noted that disease-free survival rates are greater than 90 percent at four years. Prostate cancer typically requires proton therapy five days a week for eight weeks.
Proton therapy is sometimes referred to as “bloodless surgery” because it treats the cancer with surgical precision that leaves nearby healthy tissues and organs nearly untouched. According to Dr. Jerry Slater, clinical director of Loma Linda’s Proton Therapy Center, proton therapy “allows very little scatter to the bladder and rectal areas, higher doses to the prostate, and significantly less side effects.” (National Association of Proton Therapy)
Although little research has been published on the side effects of proton radiation therapy, a recent study published in the Journal of the American Medical Association offers some insight. Researchers evaluated 280 men who had been treated with either conventional or high-dose combined photon and proton radiation for early prostate cancer. At a median of 9.4 years after treatment, patient-reported side effects were as follows for the standard versus the high-dose: urinary irritation, 23.3% vs. 24.6%; urinary incontinence, 10.6% vs. 9.7%; bowel problems, 7.7% vs. 7.9%; and sexual dysfunction, 68.2% vs. 65.9%. (Talcott)
Proton therapy is still relatively new, and so it is not widely available. Currently about 20 centers around the United States offer proton therapy. Anyone who is interested in proton therapy can discuss the option with their healthcare provider and/or contact the National Association of Proton Therapy for more information and treatment locations.
Health insurance usually covers proton therapy, but because it is more costly than other forms of radiation and not as readily available, you should consult your insurance company before committing to treatment.
AUA NY 2010 – Choosing the “right type” of radiation therapy – Slide Presentation- KRAKOW, POLAND – Presented by Glen Gejerman, MD at the Annual Meeting of the AUA – New York Section – October 3 – 9, 2010 – Kraków, Poland (PDF)
National Association of Proton Therapy: http://www.proton-therapy.org/
Talcott JA et al. Patient-reported long-term outcomes after conventional and high-dose combined proton and photon radiation for early prostate cancer. JAMA 2010 Mar 17; 303(11): 1046-53
University of Maryland Marlene and Stewart Greenebaum Cancer Center: http://www.umgcc.org/radiation_oncology_program/calypso_home.htm