Radiation therapy, or radiation oncology, involves using targeted, penetrating rays of energy (radiation) to destroy cancer cells. In the treatment of lung cancer, radiation therapy can be used before surgery to shrink a tumor or after surgery to kill any remaining cancer cells.
External beam radiation therapy is the most common form of radiation therapy used to treat lung cancer. It is produced by a machine called a linear accelerator—short, targeted bursts of x-rays are fired from the machine at the cancer.
As with any cancer treatment, a detailed treatment plan must be developed for external beam radiation therapy. The treatment plan helps determine the exact area where the treatment needs to be focused. This area is called the "treatment field."
The first step in determining the treatment field is an information-gathering process called a "simulation." Even with a patient lying still, a tumor will move during external beam radiation therapy because of breathing and other normal bodily movements.
Previously, to compensate for the movement and to ensure the entire tumor was treated, radiation oncologists had to target the tumor as well as some surrounding healthy tissue. Today, advanced technologies help radiation oncologists plan and apply external beam radiation therapies that target the tumor while sparing as much of the surrounding normal tissue as possible.
Technologies used at the Swedish Cancer Institute (SCI) to develop a treatment plan and then ultimately treat lung cancer using external beam radiation therapy include:
4D CT Imaging
The SCI was an early adopter of 4D imaging that allows physicians to visualize the motion of lung tumors over a patient's breathing cycle, resulting in improved design of each patient's treatment plan.
Image-Guided Radiation Therapy (IGRT)
Swedish was the first in the Northwest and among the first in the world to offer this innovative procedure. Radiation beams come out of the linear accelerator in a square-shaped manner. To spare as much of the surrounding normal tissue as possible, the radiation oncologist designs special blocks to shape the radiation beam. With IGRT, the linear accelerator is joined to a CT scanner. This allows for near real-time imaging of the tumor prior to treatment, improving the precision of the radiation delivery while reducing the exposure of radiation to normal tissue.
Intensity-Modulated Radiation Therapy (IMRT)
For years, Swedish physicians have been at the forefront of researching IMRT applications. With IMRT, the radiation beams are broken up into numerous pencil-sized beams. These smaller beams, or beamlets, can be conformed to the shape of the tumor in three dimensions. As a result, high doses of radiation can be directed at the cancer while reducing damage to nearby tissue.
Radiation oncologists at Swedish were among the first in the Northwest to use a 16-slice PET/CT scanner for radiation-treatment planning. The scanner combines Computerized Tomography (CT) and Positive Emission Tomography (PET), two standard medical imaging tools. The PET/CT scanner allows the tumor to be defined more precisely by better identifying the junction between cancer and inflamed normal tissue. This, in turn, allows the radiation oncologist to more effectively plan the dose of radiation to the cancer while sparing more of the healthy tissue.
Volumetric Modulated Arc Therapy (VMAT)
SCI was one of the first cancer centers in the United States to introduce this novel radiation therapy delivery technique. During VMAT treatment, the radiation machine rotates around the patient in a series of arcs delivering focused beams of radiation to the cancer. The shape and intensity of the radiation beams changes as the machine rotates. These features mean that, in effect, the beam of radiation can come from an infinite number of angles, thereby reducing the dose of radiation to normal tissue while increasing the dose to the cancer. The arc-based delivery also allows the radiation oncologist to treat tumors that are adjacent to critical structures in the body, such as a tumor that may be wrapped around an organ.
Learn more about Volumetric Modulated Arc Therapy (VMAT)
CyberKnife (Stereotactic Radiosurgery)
The Swedish Radiosurgery Center offers the first radiosurgery system accurate enough to target small and complex tumors anywhere in the body, including the lungs. Stereotactic radiosurgery, despite its name, is a non-surgical procedure that uses precisely targeted radiation to treat certain types of tumors and other inoperable medical disorders. The CyberKnife system uses a high-energy x-ray machine on a robotic arm to deliver the radiation beams.
Learn more about CyberKnife
Brachytherapy and Lung Cancer
Brachytherapy, also known as internal radiation therapy or interstitial radiation, is done by implanting a radioactive source inside or next to a cancerous tumor. At Swedish, High-Dose Rate (HDR) brachytherapy has been used in the treatment of lung cancer.
HDR involves the temporary placement of a concentrated radiation source directly in or around the tumor. The direct placement helps spare surrounding healthy tissue while the high dose can mean a shorter treatment time compared to more traditional radiation therapies.
In addition to HDR, lung-saving brachytherapy is another internal radiation therapy offered at Swedish. Lung-saving brachytherapy may be an option for high-risk patients with non-small cell lung cancers.
The SCI participated in a national, multicenter clinical research trial through the American College of Surgeons Oncology Group (ACOSOG) that offers many potential benefits for high-risk patients with non-small cell lung cancers that are three centimeters or smaller.
Lung surgeons are able to resect less of the lung as they operate because they lay down a mesh implanted with radioactive seeds, which deliver radiation to the site over a three-month period. This allows for smaller surgical margins that spare more lung tissue while 100 percent of the radiation dose is delivered within five millimeters of the seeds. Swedish surgeons first performed this procedure in 2008.
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