Radiation for prostate cancer
Here's what you should know about this treatment option.
Men who get diagnosed with prostate cancer have several options to choose from for their next step. Many men with slow-growing, low-risk cancer follow active surveillance, a wait-and-see approach that monitors the cancer for changes.
But if the cancer shows higher risk (a Gleason score of 7 or higher) or has already begun to spread, other treatments are recommended. (A Gleason score classifies prostate tumor cells on a scale from 6 to 10. The higher the number, the more likely the cancer will spread.) There are two options: surgery to remove the prostate (called a prostatectomy) or radiation to destroy the cancer cells.
Studies comparing these two approaches demonstrate no advantage of one over the other with respect to cancer control. Your path will depend on factors like your current health, the specifics of your cancer, and personal preference. Yet for many men, radiation can be the better option.
"It's much more precise than the traditional radiation used for other kinds of cancer, and research also has found that long-term quality of life is often better, with fewer adverse health effects compared to surgery," says Dr. Anthony D'Amico, a radiation oncologist with Harvard-affiliated Dana-Farber Cancer Institute and Brigham and Women's Hospital.
There are two main ways to deliver radiation to the prostate: external beam radiation and brachytherapy.
Are you a candidate?Whether your doctor recommends radiation depends on various factors, including your age, health, and personal preferences. The type of radiation is often dictated by your risk group (low, intermediate, or high) and whether the cancer is localized or has spread. Sometimes hormone therapy (called androgen suppression therapy, or ADT) is given before radiation or along with it. ADT reduces levels of male hormones, called androgens, which can slow or even stop the cancer's growth. Studies have found this one-two punch leads to higher survival rates than radiation alone among men with localized prostate cancer and a Gleason score of 7 or higher. If you opt for surgery, your doctor may suggest radiation afterward, called adjuvant radiation therapy. "You have surgery to remove cancer, and then radiation to eliminate any remaining tumor deposits to keep cancer from returning," says Dr. Anthony D'Amico, a radiation oncologist with Harvard's Dana-Farber Cancer Institute. Cancer that has grown beyond the prostate also may require post-surgery radiation. After you've had radiation, you'll have a prostate-specific antigen (PSA) test every three to six months for five years and then annually after that to check for recurrence of the cancer. "If your PSA ever rises above 2, then imaging tests are done, and if needed, additional radiation or other appropriate treatment is given," says Dr. D'Amico. |
External beam radiation
Rays of high-energy radiation are targeted to the site of the cancer on the prostate (and sometimes nearby lymph nodes). External beam radiation effectively destroys cancer cells, but it can also damage healthy tissue. A CT scan determines the prostate gland's exact location to allow for precise focusing and help limit collateral damage to the rectum and bladder. You lie on a table where a device delivers the radiation for five to 10 minutes. In general, treatments are given five days a week for several weeks. There are several types of external beam radiation therapy:
Three-dimensional conformal radiation therapy (3D-CRT). This involves taking three-dimensional pictures of the prostate and surrounding structures before treatment to pinpoint their locations. These images help the radiologist keep radiation away from the bladder and rectum.
Intensity-modulated radiation therapy (IMRT). IMRT is now the most commonly used form of radiation therapy. It is similar to 3D-CRT, but is more precise because it allows doctors to change the radiation intensity within each of several radiation beams, increasing total radiation to the cancerous area while reducing radiation to healthy tissues.
Proton beam therapy. This has the same precision as IMRT but uses protons (subatomic particles with a positive electrical charge) instead of photons (light particles) used in conventional radiation. During proton beam therapy, radiation is released in a narrow band, thus minimizing damage to surrounding tissue. The downside is that it is more expensive and not available everywhere. "Also, outcomes appear to be equivalent with IMRT in terms of curing the cancer and improving quality of life," says Dr. D'Amico.
Stereotactic body radiation therapy (SBRT). SBRT uses image guidance and computer-controlled robotics to deliver multiple radiation beams to the tumor. Several systems are available, with brand names like CyberKnife, Gamma Knife, and TomoTherapy. Long-term side effects are still being explored.
Hypofractionated radiation therapy. This delivers larger doses with each treatment, requiring fewer sessions — typically, a total of five treatments spaced out over four to five-and-a-half weeks. A man is eligible for this treatment only if he has good urinary flow, doesn't need to urinate often at night, has not had prostate surgery, and doesn't take anticoagulants (blood thinners).
Brachytherapy
Brachytherapy involves placing radioactive pellets, or "seeds" — each about the size of a grain of rice — in or near the prostate tumor. The number of seeds ranges from 50 to 150, depending on the size of the prostate gland.
After the man receives either general or spinal anesthesia, the doctor places an ultrasound probe in the rectum and a catheter in the bladder. The doctor then uses a needle to insert the seeds through the perineum (the area between the scrotum and anus) and guides them into place. The seeds are left there and, over time, emit less and less radiation until they become nonradioactive. Depending on the type of seeds, this may take anywhere from three months to a year.
If cancer returns, a doctor may suggest high-dose-rate brachytherapy. Here, the more powerful seeds are temporarily placed and then removed several days later, with the process repeated for several sessions.
Image: © Mark Kostich/Getty Images
About the Author
Matthew Solan, Executive Editor, Harvard Men's Health Watch
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