The goal of radiation therapy is to get a high enough dose of radiation into the body to kill the cancer cells while sparing the surrounding healthy tissue from damage. Several different radiation therapy techniques have been developed to accomplish this. Depending on the location, size and type of your tumor or tumors, you may receive one or a combination of these techniques. Your cancer treatment team will work with you to determine which treatment and how much radiation is best for you.
During external beam radiation therapy, a beam of radiation is directed through the skin to a tumor and the immediate surrounding area in order to destroy the main tumor and any nearby cancer cells. To minimize side effects, the treatments are typically given every day for a number of weeks.
The radiation beam comes from a machine located outside of your body that does not touch your skin or the tumor. Receiving external beam radiation is similar to having an X-ray taken. It is a painless, bloodless procedure. The most common type of machine used to deliver external beam radiation therapy is called a linear accelerator, sometimes called a “linac.” It produces a beam of high-energy X-rays or electrons. Using sophisticated treatment planning software, your radiation oncology treatment team plans the size and shape of the beam, as well as how it is directed at your body, to effectively treat your tumor while sparing the normal tissue surrounding the cancer cells.
Several special types of external beam therapy are discussed below. These are used for particular types of cancer, and your radiation oncologist will recommend one of these treatments if he or she believes it will help you.
Three-dimensional conformal radiation therapy (3DCRT)
Tumors usually have an irregular shape. Three-dimensional conformal radiation therapy (3D-CRT) uses sophisticated computers and computer assisted tomography scans (CT or CAT scans) and/or magnetic resonance imaging scans (MR or MRI scans) to create detailed, three-dimensional representations of the tumor and surrounding organs. Your radiation oncologist can then shape the radiation beams exactly to the size and shape of your tumor. The tools used to shape the radiation beams are multileaf collimators or blocks. Because the radiation beams are very precisely directed, nearby normal tissue receives less radiation exposure.
INTENSITY MODULATED RADIATION THERAPY (IMRT)
Intensity modulated radiation therapy (IMRT) is a specialized form of 3D-CRT that allows radiation to be more exactly shaped to fit your tumor. With IMRT, the radiation beam can be broken up into many “beamlets,” and the intensity of each beamlet can be adjusted individually. Using IMRT, it may be possible to further limit the exact amount of radiation that is received by normal tissues that are near the tumor. In some situations, this may also allow a higher dose of radiation to be delivered to the tumor, increasing the chance of a cure.
IMAGE GUIDED RADIATION THERAPY (IGRT)
Image-guided radiation therapy (IGRT) is used to help them better deliver the radiation dose to the cancer. Normal structures and tumors can move between treatments due to differences in organ filling or movements while breathing. IGRT is conformal radiation treatment guided by imaging equipment, such as CT, ultrasound or stereoscopic X-rays, taken in the treatment room just before the patient is given the radiation treatment. All patients first undergo a CT scan as part of the planning process. The digital information from the CT scan is then transmitted to console in the treatment room to allow doctors to compare the earlier image with the images taken just before treatment. During IGRT, doctors “fuse” these images to see if the treatment needs to be changed. This allows doctors to better target the cancer while avoiding nearby healthy tissue. In some cases, doctors will implant a tiny piece of material called a fiducial marker near or in the tumor to help them localize the tumor during IGRT.
A CT simulation for radiation therapy follows your initial consultation in our Radiation Therapy Department. CT simulation includes a CT scan of the area of your body to be treated with radiation. The CT images acquired during your scan will be reconstructed and used to design the best and most precise treatment plan for you. The simulation portion of your radiation therapy regiment ensures that your treatments will target the area of concern, while missing surrounding critical structures.
You will begin the simulation by having a CT scan of the area of your body to be treated with radiation therapy. We will ensure that you are as comfortable as possible for your scan, as the goal is to position you the same way every day during your treatment regimen. The very center of the treatment area will be defined and marked as a reference point to be used during your treatment. We may need to use permanent ink to create a very small tattoo in this area. This will be discussed with you before simulation and only takes a couple of seconds.
The second half of simulation involves the creation of an immobilization device that will be utilized over the duration of your treatment to keep you in the same position each and every time you are treated. A mask may be used for treatments near the head, and a “cradle” or “mold” may be cast around the area of interest if it is located on the torso or body . Marks will be made on the mask or mold to serve as reference points that help our radiation therapists place you in the correct and exact position every day, ensuring your treatments are as accurate and precise as possible.
WHAT IS HORMONAL THERAPY?
Hormonal therapy medicines are whole-body (systemic) treatment for hormone-receptor-positive breast cancers. Hormone receptors are like ears on breast cells that listen to signals from hormones. These signals “turn on” growth in cells that have receptors.
Most breast cancers are hormone-receptor-positive.
About 80% of breast cancers are estrogen-receptor positive.
About 65% of estrogen-receptor-positive breast cancers are also progesterone-receptor-positive.
About 13% of breast cancers are estrogen-receptor-positive and progesterone-receptor-negative.
About 2% of breast cancers are estrogen-receptor-negative and progesterone-receptor-positive.
If a cancer has receptors for either estrogen or progesterone, it’s considered hormone-receptor-positive.
WHAT DOES IGRT MEAN FOR YOU?
Hormonal therapy medicines can be used to:
- Lower the risk of early-stage hormone-receptor-positive breast cancer coming back.
- Lower the risk of hormone-receptor-positive breast cancer in women who are at high risk but haven’t been diagnosed with breast cancer.
- Help shrink or slow the growth of advanced-stage or metastatic hormone-receptor-positive breast cancers.
Proton Beam Therapy
Similar to external beam therapy, proton beam therapy is a form of radiation treatment that uses protons rather than X-rays to treat certain types of cancer and other diseases. The physical characteristics of the proton therapy beam allow doctors to better focus the dose on the tumor with the potential to reduce the dose to nearby healthy tissues.
Neutron Beam Therapy
Like proton therapy, neutron beam therapy is a specialized form of radiation therapy that can be used to treat certain tumors that are radioresistant, meaning that they are very difficult to kill using conventional radiation therapy. Neutron therapy can also be used to treat certain inoperable tumors.
Stereotactic radiotherapy is a technique that allows your radiation oncologist to precisely focus beams of radiation to destroy certain types of tumors. Since the beam is so precise, your radiation oncologist may be able to spare more normal tissue than with conventional external beam therapy. This additional precision is achieved through rigid immobilization, such as with a head frame as is used in the treatment of brain tumors. Although often performed in a single treatment, fractionated radiotherapy, where patients receive up to five treatments, is sometimes necessary. Stereotactic radiotherapy may be the only treatment if a very small area is affected. In addition to treating tumors, it can also be used to treat malformations in the brain’s blood vessels and certain noncancerous (benign) brain tumors.
Brachytherapy, also called internal radiation or seed implants, is the placement of radioactive sources in or just next to a tumor. The radioactive sources may be left in place permanently or only temporarily, depending upon your cancer. To position the sources accurately, special catheters or applicators are used. Because the radiation sources are placed so close to the tumor, your doctors can deliver a large dose of radiation directly to the cancer cells with minimal exposure to normal tissue.
The radioactive sources used in brachytherapy, such as thin wires, ribbons, capsules or seeds, come in small sealed containers. Some sources are placed permanently and are referred to as implants. These radioactive sources remain in the body after their radiation has been expended and the source is no longer radioactive. Other sources are placed temporarily inside the body, and the radioactive sources are removed after the prescribed dose of radiation has been delivered.
There are two main types of brachytherapy: intracavity treatment and interstitial treatment. With intracavity treatment, the radioactive sources are put into a space near where the tumor is located, such as the cervix, the vagina or the windpipe. With interstitial treatment, the radioactive sources are put directly into the tissues, such as the prostate.
Often these procedures require anesthesia and brief hospitalization. Patients with permanent implants may have a few restrictions at first and then can quickly return to their normal activities. Temporary implants are left inside of your body for several hours or days. While the sources are in place, you will stay in a private room. Doctors, nurses and other medical staff will continue to take care of you, but they will need to take special precautions to limit their exposure to radiation.
Devices called high dose rate remote afterloading machines allow radiation oncologists to complete brachytherapy quickly, in about 10 to 20 minutes. Powerful radioactive sources travel through small tubes called catheters to the tumor for the amount of time prescribed by your radiation oncologist. You may be able to go home shortly after the procedure. Depending on the area treated, you may receive several treatments over a number of days or weeks.
Most patients feel little discomfort during brachytherapy. If the radioactive source is held in place with an applicator, you may feel discomfort from the applicator. There are medications that can help this. If you feel weak or queasy from the anesthesia, your radiation oncologist can give you medication to make you feel better.