Radiation Therapy

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Radiation therapy is a type of cancer treatment that uses high-powered energy beams, such as X-rays, to kill cancer cells. Radiation therapy is used in an attempt to cure cancer, control cancer growth, or relieve symptoms caused by the tumor, such as pain.

How does radiation therapy work?

Radiation therapy works by damaging the cancer cells’ ability to multiply. When the cancer cells die, the body naturally eliminates them. Unlike systemic chemotherapy, which kills cancer cells wherever they are throughout the body, radiation only kills cancer cells directly in the path of the radiation beam. Because radiation also damages the normal cells in its path, care is taken to shape the radiation beams to minimize the amount received by sensitive organs. One advantage of radiation therapy is that it does not tend to cause side effects outside the treated area.1

How is radiation therapy given?

Radiation therapy is administered by a radiation oncologist, a doctor who specializes in using radiation treatments to treat cancer.

Radiation therapy can be roughly classified by the position of the radiation source. Radiation can come from a machine outside the body (external beam radiation therapy) or from radioactive material placed in the body (internal radiation therapy, more commonly called brachytherapy).

External Beam Radiation Therapy (EBRT)

When radiation therapy is directed at the lung cancer from outside the body, it is called external beam radiation therapy (EBRT). This is the type of radiation therapy most often used to treat non-small cell lung cancer. For EBRT, the radiation oncologist takes careful measurements to determine the proper dose of radiation and the correct angles for aiming the radiation beams. Treatment is similar to getting an X-ray, but the radiation dose is stronger. Each radiation therapy session is usually painless and only lasts a few minutes.

A radiation therapy schedule usually consists of a specific number of treatments given over a set period of time. For example, a standard course for lung cancer may consist of sessions 5 days per week (Monday-Friday) for 6 to 7 weeks, for a total of 30 to 35 treatments.

Radiation therapy schedule

Internal Radiation Therapy or Brachytherapy

Brachytherapy seedingWhen radiation therapy is given using implants, it is called internal radiation therapy or brachytherapy. The radiation oncologist places a small source of radioactive material, often in the form of small pellets or seeds, directly into the cancer. This is usually done during bronchoscopy or during surgery. The radiation travels only a short distance from the implanted radiation source to the tumor, which limits damaging effects on surrounding healthy tissue. The radioactive material may be removed after a short time—several minutes for high-dose-rate brachytherapy or up to a few days for low-dose-rate brachytherapy. Alternately, the “seeds” are left in place permanently, and the radiation gets weaker over time until it is all absorbed.2

What are the different types of external beam radiation therapies (EBRTs)?

Body moldStandard EBRT is used less often now since newer techniques with greater accuracy have been developed. The new techniques have resulted in better success rates and fewer side effects. In each case, the patient will often be fitted with a body mold that restricts movement.

A CT scan or MRI scan is then done to locate the tumor and surrounding organs. Radiation oncologists may use MRI or PET simulator technology to more precisely and safely target the cancer cells. To aid in daily positioning, up to a half-dozen tattoos consisting of tiny dots will be placed on the skin. During each subsequent treatment session, one or more beams are targeted at the tumor and irradiate the diseased tissue painlessly. During EBRT, the patient must remain still to avoid moving the tumor out of the focused beam.

EBRT machine

Three-dimensional conformal radiation therapy (3D-CRT)

3D-CRT uses special computers to precisely map the location of the tumor. Radiation beams are shaped and aimed at the tumor from several directions, which makes them less likely to damage normal tissues.

Intensity-modulated radiation therapy (IMRT)

IMRT is an advanced form of 3D therapy. IMRT modifies the radiation by varying the intensity of each radiation beam. This technique allows a precise adjustment of radiation doses to the tissues within the target area, possibly allowing a higher radiation dose to the tumor and keeping more radiation away from nearby normal tissues. Many major hospitals and cancer centers now use IMRT.

Image-guided radiation therapy (IGRT)

A specialized form of IMRT used in non-small cell lung cancer (NSCLC). IGRT uses sophisticated imaging tests to verify the position of the patient and the location of the tumor prior to and during the delivery of the treatment. This leads to less healthy tissue being harmed, decreased side effects, and better treatments delivered.

Stereotactic body radiation therapy (SBRT)

SBRT, or stereotactic ablative radiotherapy (SABR), is sometimes used to treat early-stage NSCLC when surgery isn’t an option due to the patient’s health or in patients who do not want surgery. It can be used for tumors small in size and confined to the lung, including lung metastasis.

SBRT combines image-guided radiation therapy (IGRT) with even more advanced techniques to precisely deliver extremely high doses of radiation to the tumor while decreasing the dose to healthy tissue nearby. Instead of giving small doses of radiation each day for several weeks, SBRT can be given in two to five treatments. When the treatment is delivered in only one session, it is referred to as stereotactic radiosurgery (SRS).

To target the radiation precisely, the patient must remain extremely still. Head frames or body molds may be used to reduce movement. Like other forms of external radiation, SBRT itself is painless. It does not require anesthesia and usually has fewer side effects than traditional methods. There are multiple stereotactic radiosurgery devices on the market right now, and they each achieve the same goal. Some brand-name machines a patient might hear about include CyberKnife and True Beam.

Proton therapy

Proton therapy is a type of radiation treatment that uses protons instead of X-rays to treat cancer. A proton is a positively charged particle that is part of an atom, the basic unit of all chemical elements.

Proton therapy has many advantages, including that it reduces the risk of radiation damage to healthy tissues, allows a higher radiation dose to be directed at some types of tumors, and may result in fewer and less severe side effects. However, proton therapy is very expensive and is not covered by all insurance companies for all diagnoses. In addition, it requires expensive and specialized equipment that only a handful of hospitals in the United States have.1,3

When is radiation therapy used in non-small cell lung cancer (NSCLC) treatment?

The type of radiation therapy most often used to treat NSCLC is external beam radiation therapy (EBRT). In patients with early-stage NSCLC, in which there is only a single small nodule in the lung without any spread to nearby lymph nodes, stereotactic body radiation therapy (SBRT) is typically given. SBRT is the standard of care for patients who cannot be treated surgically.

In more advanced stages of NSCLC, EBRT can be given alone or along with chemotherapy as the main treatment. It is also used after surgery, alone or along with chemotherapy, to try to kill any small deposits of cancer that surgery may have missed. EBRT can be used prior to surgery, as neoadjuvant therapy, typically along with chemotherapy, to try to shrink a lung tumor to make it easier to operate on. Internal radiation therapy and external beam radiation therapies are also used to shrink tumors to relieve symptoms of advanced lung cancer, such as bleeding, trouble swallowing, cough, and shortness of breath.4

When is radiation therapy given in small cell lung cancer treatment?

The type of radiation therapy most often used to treat small cell lung cancer (SCLC) is external beam radiation therapy (EBRT). Most often, radiation treatments given as the initial treatment for SCLC are administered once or twice daily, 5 days a week, for 3 to 7 weeks.

Radiation therapy schedule

EBRT is most often given at the same time as chemotherapy in limited-stage disease to treat the tumor and lymph nodes in the chest. Sometimes it is given after chemotherapy, as adjuvant therapy, to try to kill any small areas of cancer that may remain.

In extensive-stage small cell lung cancer (SCLC), EBRT may be used to shrink tumors to relieve symptoms of lung cancer such as bleeding, trouble swallowing, cough, and shortness of breath.

Since the brain is a common place for metastasis in SCLC, radiation is often given to the brain after other treatments to help lower the chances that the cancer will spread there. This type of radiation is called prophylactic cranial irradiation. Radiation to relieve symptoms and prophylactic cranial radiation are given for shorter periods, usually less than 3 weeks.5

What are the common side effects of radiation therapy?

Common side effects from radiation treatment for lung cancer may include:

  • Fatigue
  • Sunburn-like skin changes, such as dryness, itching, or peeling
  • Hair loss (in the area where the radiation enters the body)
  • Cough, difficulty breathing, and shortness of breath: these symptoms can develop as “radiation pneumonitis” up to months after therapy and may require anti-inflammatory medication
  • Sore throat and trouble swallowing
  • Loss of appetite and weight loss
  • Nausea and vomiting (when the treated area is near the stomach)

Radiation to the brain may cause:

  • Memory loss (usually short-term)
  • Headaches
  • Trouble thinking
  • Reduced sexual desire

It is important to discuss radiation therapy with the radiation oncologist before treatment begins in order to be prepared for potential side effects and to understand what can be done to treat them. The doctor can often prescribe drugs to help relieve many of these side effects. Most of these side effects go away once treatment is completed, but some can last a long time, or may even be permanent. When chemotherapy is given in combination with radiation therapy, the side effects are often worse.1,2

What’s new in lung cancer radiation therapy research?

There are currently clinical trials under way that aim to further improve the precision of imaging and radiation delivery techniques. Researchers are looking into new imaging techniques, such as four-dimensional (4D) CT scans, and are studying proton therapy more extensively.

Radiation therapy is also being studied in combination with surgery, chemotherapy, and targeted therapy.1

If you are considering participating in a clinical trial, start by asking your doctor whether there is one for which you might qualify in your area. In addition, here are several resources to help you find one that may be a good match for you:

Learn more about clinical trials here.

Questions to ask your health care team about radiation therapy

Print this list

  1. What kind of radiation therapy will I get?
  2. How can radiation therapy help?
  3. How many weeks will my course of radiation therapy last?
  4. What kinds of side effects should I expect during my course of radiation therapy?
  5. Will these side effects go away after radiation therapy is over?
  6. What kind of late side effects should I expect after radiation therapy is over?
  7. What can I do to manage these side effects?
  8. What will you do to manage these side effects?
  9. How can I learn more about radiation therapy?

Updated March 1, 2016.


  1. Bazan JG, Le Q-T, Zips D. Section 35: Radiobiology of Lung Cancer. In: Pass HI, Ball D, Scagliotti GV, eds.  The IASLC Multidisciplinary Approach to Thoracic Oncology. Aurora, CO; IASLC Press; 2014: 459-468.
  2. Lung Cancer Treatment Options. American Society of Clinical Oncology website. http://www.cancer.net/cancer-types/lung-cancer-treatment-options. Approved August 2015. Accessed March 1, 2016.
  3. Understanding Radiation Therapy. American Society of Clinical Oncology website. http://www.cancer.net/navigating-cancer-care/how-cancer-treated/radiatio.... Approved November 2015. Accessed March 1, 2016.
  4. Non-Small Cell Lung Cancer Treatment (PDQ®): Treatment Options by Stage. National Cancer Institute website. Updated May 12, 2015. Accessed March 1, 2016.
  5. Small Cell Lung Cancer Treatment (PDQ®): Treatment Options by Stage. National Cancer Institute website. Updated February 3, 2016. Accessed March 1, 2016.