What is Stereotactic Body Radiation Therapy?
- SBRT directs extremely high doses of radiation at a very precise location.
- This hyper-focused radiation prevents damage to surrounding healthy tissue.
- Higher doses of radiation mean you could complete therapy in one to five days.
Just as medications that target and shrink cancerous tumors have advanced by leaps and bounds in the past decades, radiation therapy has come quite a long way, too.
Read MoreSBRT is a hyper-focused form of radiation therapy that delivers super high doses of radiation directly to the tumor and minimal radiation to the surrounding healthy tissue. To do this, doctors use imaging to find the 3D coordinates of a tumor. They then align the radiation beam directly with the tumor as opposed to the affected tissue or bone as happens with traditional radiation. This allows for delivering much higher doses of radiation at a time and substantially reduces the effects on healthy surrounding tissue. Because of this outsized dose of radiation, for eligible patients, SBRT can do its job in as little as one day or a week at the most.
"Besides being more convenient, it's a lot more effective across many different tumor types," says Simone, who is Chief Medical Officer at New York Proton Center.
SBRT Versus Traditional Radiation
Traditional radiation is delivered at smaller doses over the course of several weeks and causes damage to the tumor's DNA. While the tumors can recover to some degree between radiation sessions, the goal is that the multiple radiation sessions damage the tumor's DNA enough that it can no longer repair itself.
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SBRT, on the other hand, involves such a high dose of radiation that the tumor can't repair itself between sessions. There may not even be more than one session. "It completely ablates the tumor, almost like you're having surgery without getting an operation," Simone says. Then, ideally, the tumor dies over the course of the next month.
Because this type of radiation doesn't affect the healthy tissue in the surrounding area, it tends to cause fewer of the sometimes serious side effects that traditional radiation can.
Who Can Get SBRT
SBRT works well in small, typically early-stage tumors throughout the body, including in the brain, lungs, prostate, liver, and spine. Again, the hyper-focused, high-dose radiation can kill tumors in these areas while sparing the otherwise healthy organ. This can reduce the risk of side effects as serious as liver failure after liver radiation and cognitive problems after whole-brain radiation.
"We're seeing some patients live years and years with brain metastases, depending on its features, because we're able to almost spot-weld any new lesions with the stereotactic treatment," Simone says.
In prostate cancer, SBRT can treat low- to intermediate-risk disease. In lung cancer, doctors use this option to treat operable tumors in people who are not candidates for surgery due to other health problems.
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"It is a well-established standard of care for patients with early stage lung cancer who otherwise are not ideal candidates for surgery," says Loo, who directs Thoracic Radiation Oncology at Stanford Cancer Institute. Emerging research suggests, he adds, that SBRT may be just as effective as surgery in anyone with an operable lung tumor. Clinical trials are currently underway to confirm this.
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Because SBRT provides a viable treatment option for many people with lung cancer who are too sick for surgery, Simone says, some data suggest this therapy has increased the overall survival of the entire lung cancer population.
A Powerful Combination
SBRT isn't only for small, operable tumors though. New research shows that it may be a powerful companion to systemic therapies, such as chemotherapy, immunotherapy and targeted drugs, in people who have advanced metastatic disease.
Systemic therapies do a good job of keeping microscopic cancer cells at bay. In many types of cancer, the newest medications are helping people live with metastatic disease for years. But, sometimes, a new tumor appears.
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Researchers are finding that rather than increase the dose of the medication, which may not work and can increase side effects, or change medications, they can apply SBRT to the new lesion, while the patient continues to take the same medication.
"We're using radiation to sort of spot-treat and eliminate the tumors that you can see and then using the chemotherapy to eliminate the microscopic cells that are spread more widely," says Loo.
New data from clinical trials suggest SBRT, used in combination with systemic therapies, boosts the effects of those other treatments, such as chemotherapy or targeted therapy.
"That's the new frontier for SBRT. The hope was once that we would develop a pill that would cure cancer and eliminate the need for radiation, but now that we have these pills and other effective drugs, they've increased the importance of localized radiation."
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