Radiation Therapy for Lung Cancer

Radiation therapy is one of the main treatments for lung cancer. Radiation therapy kills cancer cells with high-energy particles or waves. About 80% to 85% of lung cancers are non-small cell lung cancer (NSCLC). Radiation therapy can be the primary treatment in NSCLC cases where the lung tumor cannot be removed with surgery. Sometimes radiation therapy is used together with chemotherapy. Radiation therapy may be used before surgery to shrink the tumor, making it easier to operate on. After surgery, radiation therapy may be used to try to kill cancer cells that can be left behind after the tumor is removed.

Radiation therapy is also used to treat lung cancer when it has spread to other areas such as the brain or bone. In advanced NSCLC, radiation therapy can be used to shrink tumors that have spread to other organs and relieve symptoms such as pain, bleeding, trouble swallowing, and cough. The other main type of lung cancer, small-cell lung cancer (SCLC), may receive radiation therapy directed at the brain to help prevent this type of cancer from spreading to this area.

How does radiation therapy work?

Radiation therapy uses high-energy particles or waves such as x-rays, gamma rays, electron beams, or protons. While standard radiation therapy uses X-ray beams made of photons, proton therapy uses protons. Photons are bundles of energy and protons are positively charged particles located in the nucleus of an atom.

The energy from radiation, these waves or particles, breaks the DNA molecules inside cells. Cells can’t divide properly when their DNA is broken. Cancer cells are particularly susceptible to DNA damage because they grow and divide faster than most normal cells. Broken DNA stops the cancer cells from dividing and causes them to die. Radiation therapy can also damage nearby non-cancerous cells, but most of these cells are able to recover. When radiation is directed at the head, fast-dividing hair follicle cells are susceptible to damage, which may result in hair loss.

The two main types of lung cancer radiation treatments are external beam radiation therapy (EBRT) and brachytherapy, also known as internal radiation therapy. Using radiation from an external source, such as in EBRT, is more common than internally placed radiation treatments. The type of radiation most commonly used for EBRT is X-ray photons. There are several variations of EBRT, which target tumors in the lungs or tumors that have spread from the lungs to other areas including the brain.

External radiation therapy

External beam radiation therapy (EBRT) is the type of radiation therapy most often used to treat NSCLC or its spread to other organs. The radiation source is external, provided by a machine outside the body, and aimed at the area where the cancer is located. EBRT is similar to having an X-ray but with a stronger dose of radiation. The procedure itself is painless and each treatment lasts a few minutes. The patient can expect to have a series of EBRT treatments such as 5 days a week for 5 to 7 weeks. The exact treatment schedule depends on the type of EBRT used as well as other factors specific to the patient and their lung cancer.

In early-stage lung cancer, traditional EBRT was found to have inferior patient outcomes compared to surgical removal of the tumor. Patient outcomes have improved with newer types of EBRT that use stereotactic technology for more precise targeting of tumors while sparing healthy tissues.

Stereotactic body radiation therapy (SBRT)

Stereotactic body radiation therapy (SBRT), also known as stereotactic ablative radiotherapy (SABR), is a newer EBRT technique that can treat cancers more accurately and reduce the amount of exposure to radiation for nearby healthy tissues. This technique targets cancer more precisely by aiming several beams of radiation at the tumor from different angles.

Planning for SBRT involves imaging to map out how the targeted tumor area moves when the patient breathes. For SBRT, the patient receives radiation treatment while inside a specially designed body frame that reduces movement of the lung tumor caused by breathing. Tiny tracking devices in the form of gold seeds or coils may be placed inside the patient’s tumor to help doctors precisely localize the tumor. SBRT needs far fewer treatments compared to traditional EBRT. Lung cancer patients with small tumors of five centimeters or less, who are poor candidates for surgery may be recommended SBRT.

Radiation therapy with the help of 3D imaging

CT scanning is used to generate three-dimensional (3D) images of the tumor to help target the tumor in three-dimensional conformal radiation therapy (3D-CRT) and intensity-modulated radiation therapy (IMRT). 3D-CRT and IMRT are EBRT techniques that reduce radiation damage to normal tissues. 3D-CRT uses computers to map the tumor’s location and shape. Then radiation beams are shaped to match the tumor and aimed at the tumor from several directions. IMRT has the added ability to adjust the strength of the radiation beams. This additional level of control further limits the radiation dose that reaches nearby normal tissue which is why IMRT is most often used when tumors are near important structures such as the spinal cord. Volumetric modulated arc therapy (VMAT) is a type of IMRT that uses a machine that rotates around the body while delivering quick bursts of radiation.

Stereotactic radiosurgery (SRS)

Stereotactic radiosurgery (SRS) is not really a surgery as it does not involve any incisions. It is a type of radiation therapy that may be used instead of or along with surgery for single tumors that have spread from the lung to the brain. SRS is given in only one session. One method of SRS uses a machine that can focus 200 beams of radiation on the tumor from different angles over a few minutes to hours while the position of the patient’s head is maintained with a rigid frame. Another SRS method delivers radiation from a machine that moves around the head, targeting the tumor from many different angles. This later SRS method may be repeated if more treatment is needed.

Internal radiation therapy (Brachytherapy)

Brachytherapy, or internal radiation therapy, is the placing of small pellets of radioactive material into the cancer or in the airway next to the cancer. Radioactive material gives off radiation as it decays, which kills cells nearby. This procedure is sometimes used in patients with NSCLC to shrink airway tumors to relieve symptoms. The small sources of radioactive material are placed by surgery or with a bronchoscope, a flexible tube inserted through the nose or mouth. The radiation travels a short distance from the source which limits the effects on nearby tissues. The radioactive material is usually removed after a short period of time. Less often radioactive pellets or seeds are left in place and the radiation weakens over several weeks.

Patients who receive high-dose radiation in their brachytherapy treatment may need to follow safety measures for a period of time to protect others from the radiation that their internal implants will be giving off. These measures may include staying in a private hospital room, protective clothing for medical staff and not having visitors for a period after the pellets were placed.

What are the side effects of radiation therapy?

Side effects that occur with radiation therapy include fatigue, nausea, vomiting, loss of appetite, weight loss, skin redness or blistering, and hair loss. Skin changes can be treated, and the side effects of radiation therapy often go away after treatment. Side effects may be worse when radiation and chemotherapy are given together.

Radiation therapy to the chest can damage the lungs, causing a cough or breathing difficulties which may improve after treatment. Symptoms of lung damage from radiation therapy may not completely go away. Patients who receive radiation to the chest may experience radiation pneumonitis several weeks or months after radiation therapy. Radiation pneumonitis is characterized by coughing, fever, and a sensation of fullness in the chest.

The esophagus, the tube through which you swallow food, may also get damaged by radiation treatment to the chest. This is why patients may have a sore throat or trouble swallowing during treatment, and difficulty eating certain foods. Patients who receive radiation therapy to the chest may need to eat only soft foods or liquids for a while, but symptoms often improve after treatment is concluded.

Receiving radiation therapy to the brain can sometimes cause memory loss, headaches, or trouble thinking. These symptoms are considered minor compared to those caused by cancer that has spread to the brain. The patient should be aware that their quality of life can be affected by these side effects from radiation therapy.

Radiation therapy has an important role in lung cancer treatment. In cases where a lung tumor cannot be removed surgically, due to the size or location of the tumor, or the poor health of the patient, radiation therapy may be the primary treatment for lung cancer. Radiation therapy may also be used in addition to surgery and/or chemotherapy to treat lung cancer and to treat and prevent cancer that can spread from the lung to the brain.

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