You’ve just been diagnosed with the most common male cancer. Fortunately, your doctor caught your prostate cancer early, when it is 90 to 95 percent curable.
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You and your doctor may discuss active surveillance, surgery, brachytherapy or intensity-modulated radiation therapy (IMRT).
But you may want to ask about a newer option: stereotactic body radiotherapy, or SBRT.
“SBRT achieves the same high rates of cure as other therapies,” says radiation oncologist Rahul Tendulkar, MD. “But it is more convenient than IMRT and less invasive than brachytherapy or surgery.”
Technological advances over the last 10 years allow SBRT to deliver very high doses of radiation — precisely and safely — over a short period of time.
“We can visualize the target area much more clearly (within millimeters), thus limiting the dose to surrounding organs, like the rectum and bladder,” he explains.
Internal vs. external radiation
Conventional radiation therapy is delivered from either outside or inside the body:
- IMRT (intensity-modulated radiation therapy) delivers low doses of radiation to the prostate every day, for eight to nine weeks.
- Brachytherapy is a one-time procedure in which radiation seeds are implanted into the prostate.
How does SBRT compare to these conventional forms of radiation therapy?
“SBRT is similar to IMRT,” says Dr. Tendulkar. “But it is more precise, so we can deliver higher doses of radiation — over just a week and a half — without increasing side effects.”
“Brachytherapy is more invasive, requires anesthesia, and seems to have more bothersome urinary side effects than SBRT.”
The most common side effect of SBRT is urinary irritation (feelings of both frequency and urgency). Some patients may also experience a weaker stream.
“These symptoms usually go away a few weeks after SBRT, and patients typically return to baseline function within six months,” says Dr. Tendulkar.
What happens during SBRT
Before treatment, your bowels must be emptied, yet your bladder should be full. (Drinking fluid moves part of the bladder away from the target area. Clearing the bowels prevents the rectum from encroaching on the treatment area.)
When you arrive for SBRT, you’re positioned on a table, and the radiation therapist aligns you to small tattoos that are dotted on your skin. Next, a CT scanner built onto the radiation therapy machine takes a 3D image of your anatomy.
“We usually implant markers into the prostate that can act like a GPS device,” says Dr. Tendulkar.
Because of the high doses, a radiation oncologist, physicist and radiation therapist must all be present to verify that your position is perfect. If needed, they make millimeter adjustments to ensure the bladder and rectum are safely out of range.
“Once the beam is turned on, treatment takes only three to four minutes,” he says. “If the markers show us that you’re moving, we’ll pause the treatment.
“Our patients are typically in and out within half an hour.”
Because SBRT is a relatively new treatment, seek help from a center with experience in using this technology to treat prostate cancer, advises Dr. Tendulkar.
“We think SBRT will overtake IMRT in the next few years for a large number of patients,” he says.
SBRT doesn’t work for everyone, he notes. Men with very large prostate glands can experience more side effects from the very high doses. And when prostate cancer spreads beyond the prostate – into the seminal vesicles or pelvic lymph nodes, for example — IMRT is the better option.
“But SBRT is a great option for most men with early-stage prostate cancer, and we hope more and more patients will take advantage of it,” Dr. Tendulkar concludes.