Radiation therapies

ALSO KNOWN AS: Radiotherapy, external beam radiation therapy (EBRT), internal beam radiation therapy (IBRT), systemic radiation therapy, stereotactic radiosurgery, afterloading radiation, implants, brachytherapy, tomotherapy, proton therapy, intensity-modulated radiation therapy (IMRT), image-guided radiation therapy (IGRT), Mammosite therapy, radioimmunotherapy

DEFINITION: Radiation therapy uses high doses of radiation to kill cancer cells and prevent metastasis (the spread of disease). Most cancers may be treated with one or more types of radiation therapy. Most cancers may be treated by radiation therapy during the initial treatment phases. Still, a small percentage of patients may need a second course of treatment to manage symptoms caused by the growth of their tumor. The radiation oncologist, with other physicians involved in the patient’s care, will determine if the patient’s cancer is appropriately treated with radiation.

Cancers treated: Most, such as breast, prostate, thyroid, and gynecological cancers

Why performed: Radiation therapies are performed to kill, stop, or slow the growth of cancer cells in the body. Cancer is usually treated with surgery, chemotherapy, and radiation, which is called multimodal therapy. Radiation, as a component of this combined approach to care, may be used before, during, or after surgery; in combination with chemotherapy; or alone. Some patients who cannot tolerate aggressive surgeries or chemotherapies may benefit, to some degree, from radiation therapy. Many patients develop side effects from their cancers that may be treated with radiation. Spinal cord compression or bony metastases may be treated to reduce paralysis or pain.

There are three ways to administer radiation to a patient. When a machine outside the body delivers radiation to a tumor inside the body, the process is called external beam radiation therapy (EBRT). Internal beam radiation therapy (IBRT) uses sources, applicators, or a high-dose remote afterloader to place radioactive material in the body near the cancer site. Systemic radiation therapy uses a radioactive substance that is injected or swallowed and then travels to cancer cells in tissues of the body.

EBRT uses X-ray beams that may be given by a linear accelerator, a machine that generates high-energy radiation beams; by a machine with a radioactive source, cobalt 60; by a tomotherapy unit, which is a linear accelerator coupled with a computed tomography (CT) scanner that delivers radiation in spirals around the body; or by a robotically controlled accelerator that delivers radiation while tracking and controlling for patient movement or organ movement during the treatment. Proton beam therapy uses a machine that generates protons to damage cancer cells' deoxyribonucleic acid (DNA). With proton therapy, the radiation beam of protons enters the body with a low radiation dose, deposits its highest dose at the treated site, and stops without traveling through the body.

Advances in external beam therapy continue to develop. Conformal radiation therapy (3D-CRT) develops a three-dimensional tumor model and then uses shaped beams to treat the cancer from several directions. Intensity-modulated radiation therapy (IMRT) uses sophisticated treatment planning to vary the strength of the radiation beam in an attempt to lessen damage to the normal tissues surrounding the tumor. Tomotherapy is considered a type of IMRT and image-guided radiation therapy (IGRT), as the beams spiral around the body, allowing for precise and focused radiation beams based on data from a CT scan. IGRT is used to visualize the tumor location before treatment, as tumor movement occurs daily, and to control for tumor movement with respiration (respiratory gating). In addition to a CT scan, ultrasound may be used.

Stereotactic radiosurgery is a type of radiation therapy that delivers a large, precise dose to a defined tumor site. It is most commonly used for brain tumors, but applications in the abdomen and other sites are being explored. A cobalt 60 source machine is used with a head frame for brain tumors, and a robotically controlled linear accelerator may be used for brain tumors and tumors outside the head (extracranial tumors). It is called radiosurgery because of its accuracy. The radiation beam is considered as accurate as a knife (or scalpel) and may treat tumors that surgeons cannot reach using traditional surgical techniques.

Intraoperative radiation therapy is used during surgery to deliver external beam radiation directly to the tumor. The surgeon locates the cancer and moves normal tissues and organs out of the way, and then an accelerator delivers radiation directly to the tumor. The patient is asleep (under anesthesia) during the procedure, which occurs in a special lead-lined operating room.

Several methods deliver IBRT, often called brachytherapy. IBRT, using a remote-controlled machine called a high-dose remote afterloader (HDR) unit, sends high-dose radioactive material through catheters or needles placed in the patient for several minutes. Then, the sources are withdrawn, so the patient is not radioactive. When patients are exposed to radiation sources for hours or days, the process is called low-dose-rate brachytherapy. Applicators or cases that house radioactive sources are placed in the patient and left for a prescribed period. The area around the patient is considered radioactive until the source is removed. Therefore, staff must limit their exposure to the patient, and visitors are not allowed. Permanent brachytherapy is a type of low-dose therapy in which radioactive seeds are placed in the patient and remain while giving off low doses of radiation for weeks or months. The patient gives off some radioactivity in tiny doses. The primary safety consideration is to keep children away from the implant area. For example, a man undergoing permanent brachytherapy for prostate cancer must not allow children to sit on his lap.

Systemic radiation therapy is given as a capsule or liquid swallowed by the patient, or it may be given in a vein (injected intravenously). The radioactive liquid then moves throughout the body. The patient may stay in a special room in the hospital, and body fluids are handled carefully, as the radiation materials are eliminated through urine, saliva, and sweat. The patient may be discharged from the hospital when the radioactivity has dipped to safe levels. Sometimes, the patient can go home after treatment with special instructions about handling waste.

Breast cancer is one of the most commonly treated cancers using external beam radiation therapy. An HDR unit decreases the treatment time from several weeks to just five days. This procedure, often called mammosite therapy, is named after the company that initially developed the procedure for commercial use. Prostate cancer may also use external beam radiation, an HDR unit, or implantable seeds (low-dose brachytherapy) to kill cancer cells. Thyroid cancer is often treated with radioactive iodine, a systemic radiation therapy in a liquid form that the patient swallows. Gynecological cancers may be treated with an HDR unit or low-dose brachytherapy with an applicator left in for some time.

Patient preparation: The radiation oncologist, a physician with specialized training in radiation therapy care, will see the patient in a consult visit to determine if radiation therapy is appropriate for their cancer. Patients are generally referred to the radiation oncologist by the patient’s surgeon or medical oncologist. The physicians treating the patient will discuss whether external, internal, or systemic radiation is most appropriate. Before receiving treatment, patients have a simulation using a CT scanner or fluoroscopic simulator to allow the physician to visualize the area to be treated. A simulation may take up to two hours. Minor marks may be placed on the skin to assist in positioning the patient for treatment. Later in the treatment room, the marks will be used with wall-mounted positioning lasers to put the patient in the correct position to receive the treatment. The simulation data plan the radiation dose amounts given by the linear accelerator, the HDR unit, or any other radiation source, such as implantable seeds. The simulation information is given to the physicist and dosimetrist, who load the data into a sophisticated treatment-planning computer. The physician then verifies the treatment site, the treatment plan, and the radiation dose to be given.

Steps of the procedure: The radiation treatment will depend on the type of radiation therapy the patient receives. Whether external, internal, or systemic therapy is used, treatment planning is still the key to accurate radiation placement and dosing. For external beam therapy, the treatment plan will outline the patient's position on the treatment table, determine the shape of the beam, define the number of treatments to be given, and prescribe the daily and cumulative doses the patient will receive. Depending on the treatment plan, the patient has four to six weeks of treatment, five days a week, with two days off for normal cells to rest and recover. If an HDR unit is used, catheters may be implanted during surgery, or hollow needles may be placed just before the treatment. HDR treatments usually occur once or twice a day for approximately five days.

Patients receiving internal radiation still need a simulation and treatment plan. For low-dose brachytherapy, such as prostate seed implants, additional imaging studies may be needed. Seeds are implanted during a surgical procedure with the patient under general anesthesia. Low-dose brachytherapy, such as used in gynecological cancers, may use applicators that are placed in a treatment room and then loaded with the radioactive source. Patients receiving systemic radiation also need treatment planning to determine the amount of radioactive liquid needed to treat the cancer.

After the procedure: Most external beam treatments are outpatient, and the patient may leave immediately after the daily treatment. Patients are not radioactive during treatments. A few external beam treatments, such as intraoperative radiation therapy and select stereotactic radiosurgery, may require hospitalization. Internal beam radiation treatments may be done on either an inpatient or an outpatient basis, depending on the method used to deliver the radiation therapy. If an HDR unit delivers high-dose radiation, the patient may be able to go home between treatments. If the internal beam radiation therapy requires that the radioactive source stay in the patient for hours or days, the patient is usually hospitalized because bodily fluids emit radioactive waste. Systemic radiotherapy may be inpatient or outpatient.

Risks: The risks from radiation depend on the site being treated and the type of radiation therapy being used. EBRT is a local treatment, so risks involve the area around the site being treated. For example, if abdominal radiation is used, then bowel and bladder problems may develop. Skin reactions, similar to sunburn, may occur. Hair loss, called alopecia, may arise if radiation is given to the head or other body areas with hair follicles. Xerostomia, or dry mouth, may occur with radiation of the head and neck areas, and dental problems may also occur with this radiation site. Fatigue is often associated with any radiation procedure. Side effects usually dissipate in two to three months after therapy. Late side effects, those developing six or more months after therapy, may include infertility, lymphedema, joint pain, or other problems, as well as a risk of a second cancer due to radiation. There is always a risk that not all cancer cells will be killed by the radiation.

Results: Cancer cell death is expected after any radiation treatment method.

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