Radiation therapy, sometimes called radiotherapy, involves the use of high-energy rays or particles to kill cancer cells. Radiation therapy works within cancer cells by damaging their DNA, and inhibiting their ability to grow and divide. When cancerous cells try to divide, they realize their DNA has been damaged and die instead. They are then naturally eliminated from the body. Tumors that grow rapidly, such as small cell lung cancers, will discover that their DNA has been damaged more quickly, and therefore will die more quickly. Tumors that grow more slowly, such as non-small cell lung cancers, will likewise die more slowly. Healthy cells are also affected by radiation, but can repair themselves in a way cancer cells cannot.
There are two main types of radiation therapy – external beam radiation therapy and internal beam radiation therapy (brachytherapy).
External Beam Radiation Therapy
External beam radiation therapy is an effective method of delivering high-energy x-rays to the cancer. A machine called a linear accelerator focuses the radiation beam to a precise location in the body for an exact period of time. This type of radiation therapy is most often used to treat primary lung cancers or its metastasis to other organs. Each treatment lasts only a few minutes, not including setup time. Radiation treatments are typically given five days a week for several weeks.
Today, conventional external beam radiation is not used as frequently as in the past, and newer techniques are enabling doctors to more accurately treat lung cancers while minimizing exposure to nearby healthy tissue. Most doctors recommend these techniques when they are available.
- Three-dimensional conformal radiation therapy (3D-CRT) combines multiple radiation treatment fields to deliver precise doses of radiation to the lung tumor.
- Intensity modulated radiation therapy (IMRT) is a specialized form of 3D-CRT that modifies the radiation by varying the intensity of each radiation beam. This technique is often used if tumors are located near structures such as the spinal cord.
- Stereotactic body radiation therapy (SBRT) is a specialized form of IMRT that delivers high doses of radiation to small and precisely defined targets over a shortened course of therapy, often in as few as three to five treatments. This type of radiation therapy is sometimes used to treat very early stage lung cancers.
- Proton beam therapy is a type of radiation therapy that uses proton beams rather than x-rays. It is only available in a limited number of facilities at the present time.
Internal Beam Radiation Therapy (Brachytherapy)
Brachytherapy is most often used to shrink tumors and to relieve symptoms caused by lung cancer in an airway. This procedure is usually done through a bronchoscope, although it may also be done surgically. The doctor places a small amount of radioactive material, often in the form of pellets, either directly into the cancer or into the airway next to the cancer. Since the radiation only travels a short distance from the source, there are minimal effects on surrounding healthy tissues. In most cases, the radiation source is removed after a short time, and less often the “seeds” are left in place permanently and grow continually weaker over several weeks.
External beam radiation therapy is sometimes used as the primary treatment for lung cancer, often in combination with chemotherapy. This is particularly true if the tumor cannot be removed surgically due to its size or location, or because of the patient’s poor health status. If the patient’s tumor can be removed surgically, radiation therapy can be used either alone or in combination with chemotherapy after surgery to attempt to kill any remaining microscopic disease. Radiation therapy may also be used to relieve symptoms of advanced lung cancer.
Treating Lung Cancer with Radiation Therapy
For non-small cell lung cancer:
- Stage I non-small cell lung cancer is treated primarily with surgery however patients who are not surgical candidates may be treated with stereotactic body radiation therapy. An excellent alternative, it is non-invasive and is usually completed in one to five treatments.
- Stage II tumors that extend outside the lung itself or where there is early lymph node involvement are treated with surgery, followed by chemotherapy. Conventional external beam radiation therapy would most commonly be recommended for those patients whose health status excludes them from surgery.
- Stage III tumors that extend into other organs or involve lymph nodes in the mediastinum (middle of the chest) can be treated in several different ways. For some patients, chemotherapy alone or chemotherapy and radiation therapy combined (chemoradiation) followed by surgery is reasonable. For others, chemoradiation therapy without surgery is preferred. Radiation is typically given over several weeks.
- Stage IV tumors have spread from the lungs and involve other locations in the body such as the brain, the bones or the liver. Although usually treated with chemotherapy, radiation therapy may be used for local control of the tumor to prevent symptoms such as pain. Treatments typically last one to two weeks.
For small cell lung cancer:
- Limited stage small cell lung cancer is confined to the chest. It corresponds roughly to Stage I-III for non-small cell lung cancer above. It is treated primarily with simultaneous chemotherapy and radiation. Because there is a high rate of microscopic tumor deposits in the brain, prophylactic cranial irradiation is frequently given after the patient has completed chemoradiation to the chest.
- Extensive stage small cell lung cancer is metastatic disease and corresponds to Stage IV non-small cell lung cancer. It is treated primarily with chemotherapy, with radiation therapy used for local control of the tumor to prevent symptoms. Treatments typically last one to two weeks.
Side Effects of Radiation Therapy
Side effects from radiation therapy may vary from one patient to the next because the direction the beam travels through each person’s body may be different. Some people feel fine, while others are uncomfortable. Likewise, different organs respond to radiation in different ways; some may be damaged relatively quickly and side effects may appear after a short period of time, while others become damaged more slowly and the effects may not be apparent until months after treatment ends. As with any medical treatment, it is always recommended that a discussion of potential side effects is included in the doctor-patient dialogue.
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