SBRT Explained: Same Results, Less Time In Treatment For Prostate Cancer

Stereotactic body radiation therapy (SBRT) is a highly focused radiation treatment that precisely targets the prostate gland. The “stereotactic” component refers to the use of three-dimensional imaging and guidance systems to pinpoint the exact location of the prostate before each treatment session. This level of precision allows for the safe administration of a much higher radiation dose per session. It’s typically completed in just five treatments spread over one to two weeks.

Compared to conventional radiation therapy, which can require daily treatments for up to eight or nine weeks, SBRT is much more convenient for patients.

The technique is made possible by the integration of advanced technology, including:

• Image-guided radiation therapy (IGRT) with cone-beam CT scans
• MRI-based planning in some centers for better soft-tissue visualization
• Motion management techniques, including the use of fiducial markers or rectal spacers to account for organ movement

Because of these enhancements, SBRT can focus the radiation more tightly on the prostate while sparing nearby organs, like the bladder and rectum.

Typically, SBRT is given every other day over five sessions, Dr. Dal Pra explains — so a patient’s schedule might be Monday, Wednesday, and Friday, plus the following Monday and Wednesday.

“Treatment usually takes 20 to 30 minutes a day,” Dr. Dal Pra adds.

Radiation Therapy Options

There are several forms of radiation therapy used to treat prostate cancer, each differing in how the radiation is delivered, over how many treatments.

The options include:

• Conventional External Beam Radiation Therapy (EBRT): Delivered over 35–40 sessions (7-9 weeks), standard daily doses of ~1.8–2 Gy, requires a long time commitment but is well-established
• Moderately Hypofractionated Radiation: Delivered over 20-28 sessions (4-6 weeks), slightly higher dose per treatment, shown to be non-inferior to conventional EBRT in large randomized trials
• SBRT / Ultra-Hypofractionation: Only 5 treatments, typically over 1-2 weeks, dose per treatment is much higher (7–8 Gy per fraction), requires the most precise planning and delivery techniques

The key distinction lies in the number of treatments and dose per treatment. With SBRT, the biological equivalent dose (BED) is high enough to destroy prostate cancer cells efficiently, but because the radiation is so precisely delivered, damage to surrounding tissues is minimized.

Studies also report biochemical recurrence-free survival rates of 90-95% at 5 years in low- and intermediate-risk groups who receive SBRT, similar to traditional approaches.

What Are The Side Effects Of SBRT?

Although SBRT is safe and effective, it still involves radiation, and side effects may occur. These typically fall into acute (short-term) and late (long-term) categories.

Acute side effects (during and shortly after treatment) may include:

• Urinary symptoms (increased frequency, urgency, a burning sensation during urination)
• Bowel changes (looser stools, mild rectal discomfort, or occasional rectal bleeding)
• Fatigue (generally mild compared to longer treatment regimens)

These effects usually resolve within a few weeks after treatment ends.

Late side effects (months to years later) may include:

• Urinary incontinence or obstruction, though rare with modern techniques
• Erectile dysfunction, which may occur over time, especially in older men or those with prior sexual dysfunction
• Rectal bleeding or ulceration, though much less likely when rectal spacers (like SpaceOAR) are used

To minimize side effects, many treatment centers use rectal spacers (a gel or balloon-like substance injected between the prostate and rectum) and fiducial markers (tiny gold seeds implanted into the prostate) to ensure accuracy.

Am I A Candidate For SBRT?

SBRT is not suitable for every prostate cancer patient. However, it is increasingly considered an excellent option for men with:

• Low-risk or favorable intermediate-risk prostate cancer
• Gleason score ≤ 3+4
• PSA ≤ 10-20 ng/mL
• No evidence of extracapsular extension or lymph node involvement
• No significant urinary obstructive symptoms

For eligible patients, SBRT offers a convenient, highly effective, and well-tolerated treatment option for prostate cancer. By reducing the number of sessions to just five, it significantly eases the treatment burden while maintaining excellent cancer control. As with any treatment, decisions should be made in consultation with a radiation oncologist, who will evaluate your cancer characteristics, anatomy, urinary function, and personal preferences.

Questions To Ask Your Doctor

• Am I a candidate for SBRT?
• Is there any reason I should consider traditional radiation instead?
• What side effects should I be on the lookout for?
• What are my options if SBRT is not effective?

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