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Radiation Therapy

Cancer treatment may vary depending upon the type of cancer, the stage of cancer, and the goal of treatment. Often, one or more treatment modalities may be used in order to provide the most complete treatment for the patient. Increasingly, it is common to use several treatment modalities concurrently (together) or in sequence. This is referred to as multi-modality treatment of the cancer and the modalities may include surgery, chemotherapy, biological therapy, and/or radiation therapy. For the majority of newly diagnosed cancer patients, the optimal treatment may be a multi-modality approach composed of standard therapies that have been established through extensive medical research. For other patients, the most appropriate therapy may still be under investigation and may be available only through a clinical trial.

Radiation therapy works by damaging the DNA in the cancer cell, thereby disabling the cancer cells from reproducing and growing. The cancer cells then die and the cancer shrinks. The objective of radiation therapy is to kill enough cancer cells to maximize the probability of cure and minimize the side effects. Under some circumstances, radiation therapy may also be used as palliation, or palliative care, which is aimed at reducing symptoms but not curing the underlying disease.

Radiation is usually administered in the form of high-energy beams that deposit the radiation dose in the body where cancer cells are located. Radiation therapy, unlike chemotherapy, is considered a local treatment. This means that cancer cells are only killed at the location in the body where the radiation is delivered, called the radiation field. If cancer exists outside the radiation field, those cancer cells are not destroyed by the radiation.

The following is a general overview of radiation therapy, covering:

This information is intended to help educate patients about their treatment options and to facilitate a mutual or shared decision-making process with their treating cancer physician.

Techniques for Delivering Radiation Therapy

Radiation therapy may be delivered externally or internally. External radiation delivers high-energy rays directly to the cancer from a machine outside the body. Internal radiation, or brachytherapy, is the implantation of a small amount of radioactive material (seeds) in or near the cancer. Radiation can also be delivered as an isotope into a vein, as in the use of radioactive iodine for the treatment of thyroid cancer.

External Beam Radiation Therapy

EBRT is given via machines called linear accelerators, which produce high-energy external radiation beams that penetrate the tissues and deliver the radiation dose deep in the areas where the cancer resides. These modern machines and other state-of-the-art techniques have enabled radiation oncologists to significantly reduce side effects while improving the ability to deliver radiation.

EBRT is typically delivered on an outpatient basis for approximately 6 to 8 weeks. EBRT begins with a planning session, or simulation, during which the radiation oncologist places marks on the body and takes measurements in order to line up the radiation beam in the correct position for each treatment. During treatment, the patient lies on a table and is treated with radiation from multiple directions. The actual area receiving radiation treatment may be large or small, depending on the features of the cancer. Radiation can be delivered specifically to an organ or encompass the surrounding area, including the lymph nodes.

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

EBRT can be delivered more precisely by using a special computed tomography (CT) scan and a targeting computer. This capability is known as three-dimensional conformal radiation therapy, or 3D-CRT. The use of 3D-CRT appears to reduce the chance of injury to nearby body structures. Since 3D-CRT can better target the area of cancer, radiation oncologists are evaluating whether higher doses of radiation can be given safely and with greater cancer cures.

Intensity Modulated Radiation Therapy (IMRT)

IMRT is an advanced form of 3-D conformal radiation therapy that allows doctors to customize the radiation dose by modulating, or varying, the amount of radiation given to different parts of the area being treated. The radiation intensity is adjusted with the use of computer-controlled, moveable “leaves” which either block or allow the passage of radiation from the many beams that are aimed at the treatment area. The leaves are carefully adjusted according to the shape, size, and location of the tumor. As a result, more radiation can be delivered to the tumor cells while less is directed at the normal cells that are nearby.

An analogy for IMRT is a shower nozzle that shoots many different streams of water from different directions, except that each stream can be turned on or off, or set to deliver different intensities. This is unlike standard radiation techniques that allow only a constant flow of radiation from each beam.

Image-guided Radiation Therapy (IGRT)

IGRT is a new approach to delivering radiation therapy that allows for more accurate delivery of radiation to the target tissue. IGRT involves imaging during the course of radiation treatment. A computer compares images taken at the time of treatment to images taken during the planning phase. Through this process, IGRT is able to account for changes in the patient’s body or position that may shift the exact location of the cancer. This allows increased accuracy of very complex treatment approaches. It also provides documentation of the degree of accuracy. IGRT is used in conjunction with EBRT, 3D-CRT or IMRT.

Intraoperative radiation therapy (IORT)

Intraoperative radiation therapy (IORT) refers to radiation therapy that is administered directly to the area of the cancer during surgery. Potential benefits of IORT include increased doses of radiation delivered to the cancer and reduced exposure of normal tissue (normal tissue can be moved or shielded during the procedure). IORT has been used in the treatment of several types of cancer, and may be particularly useful for localized cancers that are difficult to remove completely or that have a high risk of local recurrence (recurrence near the original cancer site).

Two different approaches to delivering IORT are intraoperative electron beam radiation therapy (IOERT) and high dose rate brachytherapy (HDR-IORT).1 The choice of which approach to use depends on the nature of the cancer and the facilities available. Thanks to improvements in technology, such as the development of mobile IOERT units, treatment may be provided directly in the operating room. This avoids the need to transfer the patient from the operating room to the radiation oncology department during surgery.


Internal radiation is known by a number of names, including “brachytherapy,” “seeds,” or “implants.” These terms refer to treatment in which radioactive material is placed directly into or near the cancer. Brachytherapy may be used to provide an additional boost of radiation to an area also being treated with external radiation therapy, or may be used as the only type of radiation therapy.

Brachytherapy may be permanent or temporary. In permanent brachytherapy, radioactive seeds are inserted and permanently left in place. After the procedure, the patient will temporarily contain a small amount of radiation from the seeds, although this amount is not generally dangerous to most other people. Some physicians may advise patients to avoid close contact with young children or pregnant women for several weeks. Over time, the radioactivity diminishes.

In temporary brachytherapy, the radioactive material is inserted for a specified period of time and then removed before the patient goes home. Temporary brachytherapy may be administered at a lower dose over a longer period of time (low dose rate, or LDR) or a higher dose over a shorter period of time (high dose rate, or HDR). During LDR brachytherapy, patients are generally hospitalized for as long as the radioactive implants are in place (often two to three days). In contrast, it may be possible to receive HDR brachytherapy on an outpatient basis.

Brachytherapy has proven to be useful in the treatment of several different types of cancer, including prostate, cervix, uterus, vagina, head and neck, and breast.

Breast Brachytherapy

Breast brachytherapy is an alternative to traditional EBRT for women who choose breast conservation rather than a mastectomy. Breast conservation therapy involves removing the tumor in a procedure called a lumpectomy, and is followed by radiation therapy to reduce the likelihood of recurrence. Traditional EBRT following a lumpectomy consists of five to six weeks of radiation treatment, five days per week. With breast brachytherapy, a site-specific, prescribed dose of radiation is administered during a five-day course of therapy. Because of the relatively short duration of the treatment course, breast brachytherapy is an attractive option for women who choose lumpectomy over mastectomy, but do not wish to undergo 6 weeks of EBRT.

The procedure for breast brachytherapy involves inserting a deflated balloon into the cavity where the tumor was removed. An applicator shaft, or catheter, connects the balloon to the outside of the breast. The balloon is filled with saline, and both the balloon and the catheter remain in place during the time the woman is undergoing treatment. The radiation therapy is performed on an outpatient basis in a five-day-long, twice-per-day sequence of treatments. During the treatment, a radioactive “seed” is inserted into the catheter within the balloon in an exact dose, minimizing radiation exposure to the rest of the breast, skin, ribs, lungs, and heart. No source of radiation remains in the patient’s body between treatments or after the final procedure. The catheter and balloon are removed after the final procedure. Conventional brachytherapy for breast conservation requires the insertion of 14 to 20 catheters per procedure and is much more complex than the breast brachytherapy procedure described here.

Stereotactic Radiosurgery (SRS)

Stereotactic Radiosurgery (SRS) allows non-invasive treatment of brain tumors, arteriovenous malformation, and other selected conditions.  It is an outpatient treatment that delivers a high dose of radiation to a highly defined target.  Treatments can be prescribed to deliver the total dose of radiation in a single treatment or in a fractionated manner over a course of several weeks.

What to Expect During Radiation Treatment

Radiation treatment must be individualized for each patient depending on the size and location of their cancer. In order to tailor radiation treatment to meet the specific needs of individual patients, the radiation process involves several components, including consultation, simulation, treatment planning, and finally, the actual treatment.

Consultation: The consultation is an important visit that allows both you and the radiation oncologist to gain more information. During the consultation, the radiation oncologist will obtain a medical history and perform a physical examination. Many patients find it helpful to prepare for the consultation by bringing x-rays, medical records, a list of medications, insurance information, and referral forms.

During the consultation, the radiation oncologist may communicate a great deal of information in a short period of time. You may find it useful to prepare a list of questions prior to the consultation to assure they are all answered. You may also find it beneficial to bring another person to the consultation to help understand the information from the physician.

After the consultation, the radiation oncologist may order additional tests, await results of other pending tests or consultations, or obtain additional records and reports. Multidisciplinary care is increasingly important for optimal cancer care, therefore the radiation oncologist will typically communicate with any other treating physicians to determine the appropriate course of treatment. In addition, the radiation oncologist will likely send a complete report of their evaluation to the referring physician and any other physicians requested by the patient. Once all of the necessary information has been gathered and the treatment team has communicated, a decision may be made to use radiation treatment. At this point, the radiation oncologist will discuss the treatment plan and alternatives with you and will present a consent form for you to sign prior to treatment. It is important to read and understand the consent form prior to signing it.

CT Simulation: After the initial consultation and decision to use radiation treatment, the next session is usually a planning session, which is called a simulation. Simulation is used to determine the radiation treatment fields and most of the treatment planning. Of all the visits to the radiation oncology facility, the simulation session may actually take the most time.

The CT simulator does not deliver radiation treatment, but instead allows the radiation oncologist and technologists to see the area to be treated. Images are obtained and transferred to the planning system where a virtual 3-dimensional image of the patient is created and the treatment delivery plan is developed.

For the simulation session, temporary marks are made on your skin with magic markers to identify the treatment areas. The room is periodically darkened while the treatment fields are being set. Alignment is critical during simulation and is facilitated by lasers mounted on the wall and ceiling. Special individually constructed immobilization devices may be used to help achieve this alignment. While you may see red lines of light, the low energy lasers are for alignment purposes only and you will not feel burning or anything else from the laser light.

Once the aspects of the treatment fields are set, the technologist will take special simulation x-rays representing the treatment fields. In most centers, the patient is given multiple “tattoos,” which mark the treatment fields and replace the marks previously made with magic markers. These tattoos are not elaborate and consist of no more than pinpricks followed by ink, appearing like a small freckle. Tattoos enable the radiation technologists to set up the treatment fields each day with precision, while allowing you to wash and bathe without worrying about obscuring the marks that indicate where treatment will be delivered.

Sometimes several simulation sessions are necessary in order to optimize treatment and are often performed prior to planned “boost” or “reduced field” treatments as part of the overall treatment plan.

Treatment planning: Several steps occur after simulation and prior to treatment; however, you do not need to be present during most of these procedures. The simulation x-ray may be used to design special lead alloy blocks that are used to block normal tissues from the effects of radiation. These lead alloy blocks are placed on a plastic tray and will be attached below the head of the linear accelerator, the machine that emits the radiation, prior to each treatment. These blocks are designed to minimize the amount of radiation that is delivered to normal tissues, while maximizing the dose to the cancer site. You may need to return after simulation and prior to treatment to verify the placement of these blocks and accuracy of the treatment plan.

During treatment planning, the technologists also perform special calculations to help assure that the proper radiation dose will be delivered. Computerized treatment planning may facilitate these calculations. Computers have become extremely sophisticated in planning radiation therapy delivery. Some computers are even capable of extremely complex three-dimensional representation of the treatment area and surrounding normal tissues. If such computerized planning is necessary, the patient may be asked to have a special CT scan (a special type of x-ray device with a donut shaped opening).

It may take several days for treatment planning to be completed after simulation and prior to treatment. After all treatment planning is complete, radiation therapy treatments are ready to begin.

Radiation treatment: Radiation treatment is usually given in another room separate from the simulation room. The treatment plans and treatment fields that result from the simulation session are transferred over to the treatment room, which contains a linear accelerator focused on a patient table similar to the one in the simulation room. The treatment plan is verified and treatment started only after the radiation oncologist and technologists have rechecked the treatment field and calculations, and are thoroughly satisfied with the “setup”.

During radiation treatment, you must lie very still on the treatment table while the radiation beam is targeted to the exact area of the tumor. The machine and treatment table may rotate up to 360 degrees if the treatment requires the radiation to hit the tumor from all angles. The technologists will not be in the room during the treatment, but they will be monitoring the treatment via a video camera and an audio connection with the treatment room. You will not feel the radiation as it is being delivered.

Radiation therapy is generally given once a day, five days a week, usually at the same time each day. Occasionally, treatment is given less frequently or twice a day. The number of treatments depends on multiple factors and varies from 5-10 to 40 or more, which means that treatment may last anywhere from one to eight weeks or more. Radiation treatments are generally given as outpatient treatments and involve relatively little time each day. While the first few visits might last for an hour or more, typically a daily radiation treatment will take about 15-30 minutes in the treatment room and the actual treatment only lasts a few minutes. It is important not to miss treatments. Extending treatments beyond the recommended time period may reduce the chance of controlling the cancer.

Radiation Therapy FAQs

What is radiation therapy?

Radiation therapy, or radiotherapy, is the treatment of cancer and other diseases using ionizing radiation. This radiation can be delivered externally or internally.

How does radiation work?

Radiation therapy works by damaging the DNA in the cancer cell, thereby disabling the cancer cell from reproducing and growing. The cancer cells then die and the cancer shrinks.

Will I feel the radiation or will it hurt?

No, external beam radiation treatments are painless, like having an x-ray taken. Although radiation therapy is not painful, it can cause unwanted side effects. The skin where radiation is aimed may feel like it has been sunburned and will need to be protected from the sun.

Will I become radioactive?

External beam radiation does not cause you to become radioactive, and you pose no risk of radiation exposure to people near you. If you have a radioactive implant in place, some visitors, such as pregnant women and small children, will not be allowed to get too close and visiting time may be limited or restricted until the implant is removed. Your doctor or nurse will tell you when these precautions are necessary.

Are there risks involved with radiation therapy?

The radiation used to damage or destroy cancer cells can also damage normal cells. When this happens, you may experience side effects. However, the risk of side effects is usually outweighed by the benefits of killing cancer cells. Any side effects will be carefully monitored by the radiation oncologist.

What should I know about the risks of radiation therapy?

The risks, problems, and side effects that can occur with radiation therapy depend on the type and the dose and the part of the body that is being treated. Radiation that involves the abdomen may cause diarrhea; radiation involving the head and neck can cause mouth sores. The most common side effects of radiation are fatigue, mouth sores, and skin problems. Before your treatments, your doctor will explain ways to help prevent or reduce potential side effects.

What are the typical side effects of radiation therapy?

The most common side effects of radiation therapy reported by patients are fatigue and skin irritation at the site of treatment. Other side effects depend on the area of the body being treated and the dosage being given, such as:

  • Dry or sore mouth or throat may occur when treatment is being given in the mouth, throat or neck area.
  • Some coughing and excess mucus production may occur if treatment is given to the lung area.
  • Mild nausea and/or diarrhea may occur if treatment involves the abdominal area.

Most of these side effects will go away on their own within 4 to 6 weeks after treatment is completed. Some long-term effects may include changes in the color and elasticity of skin in the treatment area. Discuss any concerns you may have about side effects and ask about medications to counteract them with the radiation oncologist before the start of your treatment.

Will the radiation therapy make me sick?

Most patients do not experience any nausea with radiation therapy, unless the area being treated with radiation is around the stomach. If you experience nausea, report this and any other symptoms to your doctor. Effective medications exist to reduce and/or prevent your symptoms.

Will I lose my hair?

No, you will not lose the hair on your head unless that is the area being treated. Hair loss only occurs in the area that is being treated with radiation therapy. For instance, if the area being treated is your arm, you can expect to lose the hair on that arm during the treatment.

How long will my radiation treatment take?

Most of the time, external beam radiation is delivered in daily treatments, or fractions, over a period of 5 to 7 weeks. The patient will generally receive these treatments Monday through Friday, and then have the weekend off. A daily fraction will take about 15-30 minutes in the treatment room; however, the actual treatment only lasts a few minutes.

Who will administer my radiation treatments?

A doctor who specializes in radiation therapy is called a radiation oncologist. The radiation oncologist will prescribe the type and amount of radiation treatment that is appropriate and work closely with a team of healthcare professionals in determining the best way to deliver that treatment. Those healthcare professionals may include the following:

  • Radiation physicists are experts who make sure the machines are working properly and that they deliver accurate radiation doses. The physicist also works closely with the doctor in planning your treatment.
  • Dosimetrists are specialists who work with the doctor and physicist to create the treatment plan and calculate the radiation dose delivered to the tumor and the surrounding normal tissues.
  • Radiation therapists are professionals who position you and operate the machines to deliver the radiation treatment on the linear accelerator.
  • Radiation oncology nurses are caregivers who will help coordinate your care, manage side effects, and help you and your family learn about your treatment.

Can someone come to my treatments with me?

Friends or family are welcome to accompany you to your treatments. However, federal regulations prohibit anyone who is not a patient or a person wearing a film badge monitor to be in the radiation controlled area during the time radiation equipment is being operated. Those accompanying you will likely be asked to wait in the reception area during the treatment. This also serves to protect the privacy of other patients. Only patients and staff are allowed in the treatment area during treatment hours.

Can I continue my regular routine/activities while undergoing radiation treatments?

You should continue with your normal routines. Most patients continue full-time occupations or leisure activities through the course of treatments. When you feel tired, do not over exert yourself; take time to rest when needed. Try to get plenty of sleep and maintain a healthy diet.

Will I be alone during my treatments?

Because radiation effects are accumulated and radiation therapists treat many patients each day, it would be a long-term health risk for them to be in the room during the radiation treatments. To ensure that you are okay and your treatment delivery is going well, you will be in voice contact with your radiation therapists and constantly monitored by a video camera. If you should need assistance, simply tell the therapists and they will terminate the treatment and immediately tend to your needs.

What cancers are treated with brachytherapy?

Brachytherapy is used predominantly to treat early stage prostate cancer; however, it may also be used in breast, cervical, head and neck, and other cancers.

What is involved in the implantation of a radioactive seed into the prostate (brachytherapy)?

For most of these patients, radioactive seed implantation into the prostate is a one-time, non-surgical, low-impact procedure. Radioactive seed implantation into the prostate is typically performed in an outpatient hospital setting by a team of physicians consisting of a urologist, radiation oncologist, and a radiation physicist. Spinal anesthesia is typically performed, but general anesthesia may occasionally be utilized. Some centers perform this procedure in their hospital operating rooms. Both outpatient and inpatient settings are acceptable. Most patients can return to normal activity, including work, within one to three days, with little or no pain.

Will radioactive seeds be painful?

After the implantation of radioactive seeds into the prostate, there typically is some soreness underneath the scrotum. Occasionally patients describe feeling like they are “sitting on a golf ball”. This is due to the slight swelling and bleeding associated with the surgery. It gradually resolves. Most patients require only mild analgesics like acetaminophen (Tylenol®). Narcotic pain medications are rarely required.

How soon after implantation of radioactive seeds into the prostate can I resume exercise or other vigorous activities?

The insertion of the needles causes some trauma to the vessels surrounding the prostate. Therefore, immediately after the implant, any exercise or activity that puts pressure on the prostate should be avoided. You should avoid lifting heavy objects or doing vigorous exercise for at least three to four days after the implant. Very vigorous exercise after this period may cause some minor bleeding in the bladder. This is not harmful, but you should limit your exercise until the bleeding stops. Activities such as bike riding, horseback riding, motorcycle riding in which there is pressure on the prostate should be avoided for at least six months. The repetitious jarring of the prostate with these activities can cause some swelling and impair urination.

Will I be radioactive after the seed implantation?

No. Although the seeds are radioactive, patients are not. Because the radioactivity is so low and the placement is so precise, virtually all the radioactivity is absorbed into the prostate. However, special precautions should be taken when a patient is in contact with small children and pregnant women in the first two months after treatment. You nurse or doctor will advise you what precautions are necessary and when.

Does the radiation from seed implants pose any danger to my sexual partner?

No, the seeds are of low energy and pose little risk to your partner. The semen is not radioactive. You may resume sexual activity very soon after the procedure. Occasionally, there may be blood in the semen or some slight pain at climax.


1 Willett CG, Czito BG, Tyler DS. Intraoperative Radiation Therapy. Journal of Clinical Oncology. 2007;25:971-977.

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Radiation Therapy

Radiation therapy is the use of high-energy X-rays to stop cancer cells from growing and multiplying. About half of all people with cancer receive radiation treatment, and for many individuals, radiation is the only cancer treatment they need.

Jana King

Patient Story: Jana King

“Often, you think ‘Oh, I’ll get a mammogram this year if I get around to it.’ But I have told my daughters, all of my friends, and former colleagues what I’ve discovered. Mammograms are useful. They’re important, and they can save lives.”