SBRT (Stereotactic Body Radiotherapy)

SBRT for Primary Lung Cancer and Oligometastases

Doctor with lung X-ray

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SBRT (stereotactic body radiotherapy) is a relatively new procedure for treating lung cancer or isolated cancer metastases to the lung, liver, or brain. Compared with conventional radiation, it uses high doses of radiation delivered to a very precise target. By using special positioning and implanted markers in the body, radiologists are able to deliver a much higher dose of radiation to a cancer than traditional radiation therapy, while sparing healthy tissue.

In treating metastases (from different types of cancer) it may improve survival. In a 2018 study looking at people with metastases from different types of cancer including lung cancer, it was found that using SBRT for up to 5 metastases increased survival without reducing quality of life. It is also being evaluated for its efficacy in treating stage I lung cancer in comparison with surgery.

Uses

At this time, there are a few reasons why SBRT may be used with cancer.

  • With lung cancer, SBRT is typically used for early stage, small lung cancers (non-small cell lung cancer) who are unable to have surgery for some reason. A lung cancer could be considered inoperable lung cancer due to the location of the tumor, or other health conditions which could make lung cancer surgery risky. It might also be considered for elderly patients who may be expected to do poorly with surgery or have medical conditions which may raise the risk of surgery complications.
  • For one or a few areas of spread of a cancer (oligometastases) to areas such as the brain, lungs, liver, or adrenal glands.

Procedure

Stereotactic body radiotherapy uses a high dose of radiation delivered to a very precise region of tissue. This is in contrast to conventional radiation therapy for lung cancer which uses a much smaller dose of radiation given over time. Radiologists map out coordinates in 4 dimensions to accurately define the area to be treated.

SBRT for Primary Lung Cancer

SBRT can sometimes work as effectively as surgery for some people with small non-small cell lung cancers which are otherwise inoperable, or in patients who have medical conditions which could make surgery dangerous. SBRT has resulted in control of the disease comparable to surgery, and long-term survival has been possible in people carefully chosen for the procedure. Tumors need to be small, usually less than 5 cm (2-3 inches) in diameter, and not be too close to the airways or the heart.

SBRT Very Effective for Stage I Inoperable Lung Cancer

According to a 2019 study published in The Lancet Oncology, SBRT nearly doubles survival in people with stage I inoperable lung cancer when compared with standard radiation therapy.

SBRT for Oligometastases

In the past, the presence of metastases limited treatment options to chemotherapy, and survival less than a year was the rule. For people that have only one or a few areas of cancer metastases (spread) the use of SBRT has changed that somewhat. It's been found that for people with oligometastases (oligo means literally "few') treating the metastases with SBRT has increased median survival rates and there have been some people who have survived long term due to this treatment. 

Lung cancer most commonly spreads to the brain, bones, the liver, and the adrenal glands, with SBRT used most often for people with liver metastases and brain metastases due to lung cancer. Due to advances in the treatment of oligometastases it has become possible for some people with lung cancer to experience extended periods of disease-free survival with a better quality of life than would otherwise be possible. (Some treatments such as targeted therapies for ALK positive lung cancer and more appear to penetrate the blood brain barrier. In fact, at the end of 2018 it was noted that people who have stage 4 ALK positive lung cancer with brain metastases had a median survival of 6.8 years when treated appropriately).

In the 2018 study noted above, the treatment of up to 5 metastases (to one or more areas) improved survival, with the 1-year survival rate being 84 percent and the 5-year survival rate 43 percent (this survival rate included people with different types of cancer including lung cancer). Patient reported quality of life was no worse immediately after the procedure, and was actually better at 6 months and 12 months following SBRT.

Possible Complications

Potential complications of SBRT depend on where it is being used and whether it is being used for a primary cancer or for a metastasis.

Complications as a Primary Treatment for Lung Cancer

There are many potential complications of SBRT for lung cancer, similar to side effects of conventional radiation therapy such as fatigue and radiation pneumonitis. Two of the more common complications of SBRT used for lung cancer include:

  • Brachial plexopathy: Radiation can damage nerves in an area called the brachial plexus. This may result in pain in the arm or shoulder, with weakness and then numbness of the hand and wrist.
  • Chest wall pain or dysfunction: If a tumor is near the chest wall, scar tissue may cause pain and restriction.

Complications of Treating Oligometastases

With brain metastases, the risk of cognitive dysfunction with radiation is always a concern, though it appears this is much less of a problem with SBRT than with conventional radiation.

The Future

Early results showing results with SBRT comparable to lung cancer surgery raise the hope that, for some people anyway, SBRT may be used as a less invasive alternative to lung cancer surgery in the future. It's also likely that, with better treatments of lung cancer now being approved and in clinical trials, and with initial results found with metastases, that SBRT may also be used further to remove sites of metastatic tumor.

Also Known As: stereotactic radiotherapy, stereotactic radiosurgery, stereotactic radiation therapy

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