Judith Bosco
External beam radiation therapy (EBRT) is a type of radiation therapy and cancer treatment option that transmits doses of radiation to the body in order to destroy cancer cells and shrink tumors. In this therapy, a beam of radiation from outside the body is directed at cancerous tissues. The treatment is painless and lasts only about five minutes. It is a local treatment, designed to treat only a specific part of the patient’s body. For instance, a breast cancer patient would only receive external radiation therapy on their breast. This is done in order to minimize severe damage inflicted on normal tissue.
In external beam radiation therapy, a linear accelerator (a special X-ray machine) transmits high-energy rays to the targeted tumor. The machine molds radiation beams to the outline of the tumor and delivers radiation from any angle. The linear accelerator does not come in contact with the patient while transmitting radiation to the cancer cells.
In external beam radiation therapy, there are three types of radiation beams: photon beams, proton beams, and electron beams. Photon beams reach tumors deep inside the body, and as they travel through the body, bits of radiation are distributed along their path. Photon beams do not stop when the tumor is reached and go into the normal tissue near the tumor. Proton beams can also reach tumors deep inside the body, but they do not scatter bits of radiation along their path, and they stop once the tumor is reached. Electron beams cannot travel deep into the body tissue, so they are only used on tumors located on the surface of the skin, or near the surface.
External beam radiation therapy is used to treat a myriad of cancer types including: breast cancer, lung cancer, prostate cancer, kidney cancer, and leukemia. Radiation therapy can be used in the early stages of cancer or after it has started to spread. When external beam radiation therapy is used in the early stages of cancer, patients tend to have higher success rates usually around 90% or higher. It is considered the most effective cancer treatment after surgery, but the efficacy varies from person to person, and cancer to cancer.
Radiation therapy can damage healthy cells and this can engender side effects. Side effects of external beam radiation therapy differ depending on the part of the body being treated and the duration of the treatment. Common side effects include: skin alterations, fatigue, nausea, hair loss, swelling, and inflammation.
There are six types of external beam radiation therapy: 3-D conformal radiation therapy(3D-CRT), intensity-modulated radiation therapy (IMRT), image-guided radiation therapy(IGRT), tomotherapy, stereotactic radiosurgery, and stereotactic body radiation therapy. In 3-D conformal radiation(3D-CRT), radiation beams conform to the shape of the tumor, and this shaping allows normal tissue to be spared while enabling higher doses of radiation to be used. Intensity-modulated radiation therapy(IMRT) is similar to 3D-CRT but smaller beams are used and the strength of the beams can be altered to give varying amounts of doses to certain parts of the tumor. Tomotherapy is a type of IMRT that takes images of the tumor before treatment to enable precise tumor targeting. It rotates around the patient during treatment and transmits radiation in a spiral pattern. Image-guided radiation therapy (IGRT) is where imaging scans are performed before each treatment. Stereotactic radiosurgery is a type of radiation treatment where high-energy beams are used to treat small tumors in the brain and central nervous system. Stereotactic body radiation therapy is similar to stereo radiosurgery but is only used for remote minuscule tumors outside the brain and spinal cord, usually in the lung or liver.