SBRT, or stereotactic body radiation therapy, is a type of radiation treatment that delivers very high doses of radiation to a tumor in just one to five sessions, compared to the 25 to 40 sessions typical of conventional radiation. It uses advanced imaging and precise targeting to focus multiple radiation beams on a small area, destroying the tumor while limiting damage to surrounding healthy tissue. SBRT is sometimes called radiosurgery, though no actual cutting is involved.
How SBRT Destroys Tumors
Conventional radiation works primarily by damaging the DNA inside cancer cells so they can no longer divide. SBRT does this too, but because each dose is so much higher (typically above 10 Gy per session), it triggers additional mechanisms that conventional radiation does not.
At these high doses, the blood vessels feeding the tumor sustain significant damage. Without a blood supply, cancer cells that survived the direct radiation hit are starved of oxygen and nutrients. This vascular damage is a major reason SBRT can be so effective against small, well-defined tumors. High-dose radiation also appears to stimulate the immune system to recognize and attack tumor cells, adding a third layer of cancer-killing activity on top of direct DNA damage and blood vessel destruction.
Cancers Commonly Treated With SBRT
SBRT works best on tumors that are relatively small, clearly defined on imaging, and not too close to sensitive structures. The most established uses include:
- Early-stage lung cancer. SBRT is the standard treatment for patients with early-stage non-small cell lung cancer who cannot undergo surgery, whether because of age, poor lung function, or other health conditions. A retrospective study of 215 patients found five-year overall survival of nearly 64%, with local recurrence rates of only about 9% at five years. For a nonsurgical treatment, those numbers are strong.
- Prostate cancer. SBRT has become an increasingly common option for low-risk and intermediate-risk prostate cancer. A study following 97 patients found that 92% were free of biochemical recurrence at five years, with results holding up well even at nine years (about 88%). Treatment is typically completed in five sessions over one to two weeks, compared to the seven or eight weeks required for conventional prostate radiation.
- Liver tumors. Both primary liver cancers and metastases that have spread to the liver from other sites are treated with SBRT, particularly when surgery is not an option. Tumors up to about 10 cm have been treated, though outcomes are generally better with smaller tumors.
- Oligometastases. When cancer has spread to only a few sites (typically five or fewer), SBRT can target each metastasis individually. Research in lung and prostate cancer has shown that treating all oligometastatic sites with SBRT can improve survival compared to standard approaches that focus only on the primary tumor.
SBRT is also used for tumors in the spine, pancreas, kidney, and adrenal glands, though the evidence base varies by site.
What Treatment Feels Like
Each SBRT session typically lasts 30 to 90 minutes, though much of that time is spent on positioning and imaging rather than the radiation itself. You lie on a treatment table while the machine rotates around you, delivering radiation from many different angles. The beams converge on the tumor, so the target receives a very high dose while each individual beam passing through healthy tissue delivers a relatively low one.
You won’t feel the radiation during treatment. There is no heat, no pain, and no sensation at all. The biggest challenge for most patients is simply holding still. Depending on the tumor location, you may be fitted with a custom body mold or frame that helps keep you in exactly the right position. Some systems also track your breathing in real time, adjusting the radiation beam to follow the tumor as it moves with each breath.
Because SBRT requires only one to five visits, the overall time commitment is dramatically shorter than conventional radiation. Many patients complete their entire course within a single week.
Side Effects by Treatment Site
SBRT generally causes fewer side effects than conventional radiation because healthy tissue receives less total radiation exposure. That said, the high dose per session means side effects are possible, and they vary depending on where the tumor is located.
For lung tumors, the most common issues are shortness of breath, a dry cough, and chest wall pain. These result from inflammation in the lung tissue and irritation of nerve endings in the chest wall. Most of these effects are temporary, though some patients notice mild breathing changes that persist.
For liver tumors, nausea and diarrhea are the primary concerns. These are usually manageable with dietary changes and medication. The treatment team carefully calculates how much of the healthy liver is exposed to radiation, aiming to preserve at least 700 mL of functional liver tissue.
For prostate treatment, patients may experience temporary urinary frequency, urgency, or mild rectal irritation. These effects typically develop in the days following treatment and resolve within a few weeks. Fatigue is possible with any SBRT site but tends to be milder than with longer radiation courses.
Who Is a Good Candidate
The ideal SBRT candidate has a tumor that is relatively small and well-separated from critical structures like the spinal cord, major blood vessels, or the bowel. For lung cancer, tumors under about 5 cm that sit in the outer portions of the lung are the most straightforward to treat. Tumors near the center of the chest, close to the heart or major airways, require more caution and modified dosing.
Tumor size matters because SBRT’s precision advantage diminishes as the target grows. Larger tumors require larger radiation fields, which exposes more healthy tissue to high doses. For liver tumors, outcomes are best when the tumor is under 4 cm, though tumors up to 10 cm and beyond have been treated when no better options exist.
SBRT is not typically used when there are too many tumors to target individually, when a tumor wraps around or directly invades a critical organ, or when the patient cannot lie still long enough for precise targeting. Previous radiation to the same area may also limit whether SBRT is safe, since tissues have a cumulative tolerance for radiation exposure.
How SBRT Compares to Surgery
For early-stage lung cancer, surgery remains the gold standard when a patient is healthy enough to undergo it. But for patients who are not surgical candidates, SBRT offers local control rates that approach surgical outcomes, with five-year local recurrence under 10%. Recovery is also dramatically easier: there is no incision, no hospital stay, and no weeks of surgical recovery.
For prostate cancer, the comparison is more nuanced. SBRT, conventional radiation, and surgery all produce similar long-term cancer control for low and intermediate-risk disease. The choice often comes down to side effect profiles and patient preference. SBRT’s appeal in prostate cancer is largely practical: five treatments versus 40 or more, with comparable outcomes.
In the liver, SBRT fills a different niche entirely. Many liver tumors are inoperable because of their location, the number of lesions, or the patient’s underlying liver disease. SBRT provides a noninvasive way to treat these tumors when surgery is off the table.