When researchers started thinking about a new way to deliver radiation therapy, it seemed like a radical idea. The proposal was to focus a very high dose on a very small area of the body, effectively delivering the same amount of radiation in three to five days that is typically given over six weeks. This would allow people to finish their treatment much sooner – but would it be safe?
The answer turned out to be yes. Stereotactic body radiation therapy is not only safe, but it has higher cure rates and fewer side effects than traditional radiation treatments. It also provides an option for some people whose cancer has spread or who can’t tolerate surgery.
How it works
With stereotactic body radiation therapy, or SBRT, multiple beams of radiation are focused on a highly precise area. To determine this area, radiation oncologists use the latest imaging techniques to measure not only the exact location of the tumor but also how it moves as the person breathes. Doctors call this four-dimensional mapping, since it includes time in the calculations. The treatments incorporate both the tumor location and movement, and the result is a personalized profile of the tumor that minimizes radiation to surrounding healthy tissue.
A typical session of SBRT lasts between 35 to 45 minutes. The person lies on a specially made body cradle or mold that helps minimize movement during the treatment. Arms are positioned above the head; remaining still in this position is usually the hardest part of SBRT.
Most people get three to five treatments, which can be on consecutive days or spaced over a week or longer. Traditional radiation treatments are shorter, at 15 to 20 minutes per session. However, they are given daily for up to six weeks.
Advantages of SBRT
SBRT is most commonly used to treat early lung cancer, and also for some early cancers of the liver, prostate, kidney, pancreas and some others. It’s very useful for people who can’t tolerate surgery, such as those with liver cancer who have liver failure, or those with lung cancer who are smokers or dependent on oxygen.
Since it minimizes radiation to healthy organs and tissues, SBRT causes far fewer side effects. For example, while conventional radiation therapy for lung cancer can lead to severe fatigue, painful swallowing, weight loss and a dry cough, most people who get SBRT have only mild fatigue or possibly a dry cough that goes away in about a week.
At the same time, the higher dose of radiation with SBRT is very effective at destroying cancer cells. Depending on the size and location of the tumor, success rates are as high as 80 percent to 90 percent.
Not for everyone
Since SBRT uses a high dose of radiation, there are limitations on how it is used. It’s not typically recommended for tumors that measure over five centimeters or are close to critical structures like the esophagus or major blood vessels. SBRT is also ruled out for most cancers that have spread to lymph nodes. Treating these cancers with SBRT would expose more normal tissue to radiation and increase side effects and other problems.
In some special cases SBRT can benefit people with cancer that has spread. For example, when breast cancer has metastasized to a small number of sites it can sometimes be controlled for years with SBRT in combination with chemotherapy. This also is the case with colon cancer, melanoma and kidney cancer that has spread to just a few places.
Advances in cancer treatment, such as SBRT and immunotherapy, are increasing survival rates for many people. While these therapies now work for only a limited number of cancers, researchers are working to find ways to help more and more people.
To learn more about research into new ways to prevent and treat cancer, visit the American Cancer Society online at cancer.org and click on Explore Research.