Radiation Therapy: An Introduction
What is radiation therapy?
Radiation therapy uses focused, high-energy photon beams to destroy cancer cells. More than half of cancer patients will undergo some sort radiation therapy. It can be used as a standalone treatment or in combination with other therapies, shrinking tumors before surgery or chemotherapy or destroying any cancer cells that might remain after other treatments.
Radiation is produced by a linear accelerator, or LINAC. It employs microwave energy to accelerate electrons to nearly the speed of light within a contained area. The electrons collide with a metal barrier, creating powerful X-rays called photons. The photons are shaped into beams and delivered to the patient through a gantry that moves 360 degrees around the treatment table.
A single dose of radiation is called a fraction. Most radiation treatments require several fractions. A typical radiation treatment plan has five fractions a week for four to six weeks.
Radiation therapy requires careful planning to ensure the tumor is targeted with the least amount of impact on surrounding tissues. CT scanners simulate treatments by testing various beam fields and immobilization devices used to keep the patient from moving during treatment. Data from the simulators help calculate the appropriate dose before treatment begins.
Types of Radiation Therapy
Also called internal radiation, brachytherapy involves radioactive material that is implanted in the body. Dozens of tiny "seeds" containing radioactive iodine are placed at the tumor site with a special needle or catheter. In permanent brachytherapy, the seeds are left inside the body to release radiation over time. For temporary brachytherapy, the seeds are inserted for several minutes or hours and removed afterward, usually in an outpatient procedure. Read more about brachytherapy
3D conformal radiation therapy
This technique that uses three-dimensional scans to determine the exact shape and size of the tumor. The radiation beams are shaped by tiny metal leaves that are arranged to fit the tumor dimensions (multi-leaf collimator), minimizing the side effects to healthy tissue.
Intensity modulated radiation therapy (IMRT)
IMRT focuses multiple radiation beams of different intensities directly on the tumor for the highest possible dose. Radiation oncologists use special planning software to make sure the patient is properly positioned for the most accurate treatment.
Intraoperative radiation therapy (IORT)
IORT is used to treat an exposed tumor during cancer surgery. IORT is performed with a treatment unit that delivers a high dose of radiation to a surgically exposed treatment area. Surrounding healthy organs and tissues protected by lead shields or moved out of the radiation field.
Proton Therapy uses energy from protons instead of photons. Protons deliver their maximum amount of energy to the tumor with a minimal entrance or exit dose, resulting in fewer side effects than standard radiation therapy. MD Anderson’s Proton Therapy Center treats several types of cancer. Read more about proton therapy
Stereotactic radiosurgery (SRS)
Stereotactic radiosurgery is not actually surgery. Instead, uses dozens of tiny radiation beams to treat tumors in the head and neck with a single radiation dose. MD Anderson uses the Gamma Knife® SRS system. Read more about stereotactic radiosurgery
Stereotactic body radiation therapy (SBRT)
SBRT links CT scans of the tumor site with treatment-planning software to determine beam direction and intensity, accounting for tumor motion and anatomy changes during the treatment procedure. Read more about SBRT
Stereotactic spine radiotherapy
Stereotactic spine radiotherapy uses guidance from CT scans for the highest possible dose to tumors on the spine. The CT machine moves on rails around the treatment table to constantly confirm the tumor location. Radiation beams can be instantly adjusted to account for any changes during the procedure.
More than half of cancer patients will receive radiation therapy, but what is it? Does it hurt? And what are the side effects?
We spoke with Cullen Taniguchi, M.D., Ph.D., to answer some common questions about radiation therapy. Here’s what he had to share.
How does radiation therapy work?
Radiation therapy uses high-energy waves, like those used with an X-ray, but at a higher energy that damages tumor cells’ DNA. The tumor cells die, but the surrounding normal tissues heal themselves.
When is radiation therapy typically used?
There are three ways radiation is used. Most commonly, radiation is used before surgery to shrink a tumor so that it’s easier to remove. We also give radiation after surgery to help destroy any remaining cancer. And when tumors can’t be easily removed with surgery, we’ll use radiation instead.
What are the different types of radiation therapy?
A second type of radiation uses photons, which you may know as X-rays. We first identify the tumor’s location with a CT scan. Then, we develop a plan to ensure as little normal tissue is exposed to radiation as possible. Intensity-modulated radiation therapy (IMRT) is a type of photon therapy that uses a powerful computer to help develop the treatment plan. The computer uses multiple angles to identify the best approach to kill the tumor and limit exposure to normal tissue. IMRT is used when a tumor is close to sensitive organs, such as with anal cancer where the tumor is near the small intestine and genitalia.
The third type of radiation therapy is proton therapy. It’s different from other types of radiation in that the energy waves don’t pass through your body and instead stop at the tumor site. This limits radiation exposure to healthy tissues. Currently, proton therapy is used to treat prostate cancer, lung cancer, head and neck cancers, liver cancer, bile duct cancer and pediatric tumors.
What should I expect the day of my first radiation?
It’s just like getting a CT scan. You’ll walk into a large room that has a table and an open-air machine. The machine is equipped with cameras and microphones so we can talk during the treatment. You’ll lie down on a table, and the machine will circle around you. You won’t ever see the radiation, and you won’t feel it at your first treatment.
What are common radiation therapy side effects?
Side effects depend on the site of your radiation, but a universal one is fatigue. My patients say they feel like they need an extra nap in the afternoon, and I say listen to your body.
Some patients also have nausea, and we have good medications to provide relief. Other common side effects include skin redness and diarrhea.
Some side effects don’t show up until some time has passed -- in some cases years. In terms of long-term side effects, patients may also experience skin changes, such as hardening and darkening, at the site of treatment.
The patients that do the best are those who get ahead of the symptoms, so talk to your care team early on about possible side effects.
What lifestyles changes should I make while receiving radiation therapy?
Focus on good nutrition. You’ll need to consume more calories than usual to fuel the body’s work of repairing any damage to normal tissues surrounding the treatment site.
Unfortunately, it’s very common to not have an appetite because of the cancer or the treatment, but I tell patients to think of food as a prescription. You need to get the right nutrition to help with healing. If you’re an MD Anderson patient, ask for a referral to see one of our dietitians if you’re having trouble eating.
I also recommend patients be as active as their bodies will let them. Staying active is good for the body and the mind, though this isn’t the time to start a new fitness regimen.
What’s new with radiation therapy?
One innovation is stereotactic radiation, which is a form of IMRT. It allows us to safely deliver a radiation at such as high dose that we can shorten the length of treatment to as little as one week, and sometimes even one day. By reducing the treatment period, a patient can receive radiation during a “down week” of their chemotherapy schedule. It’s more convenient, and it can cost less than standard radiation treatments. Stereotactic radiation is already being used for lung cancer and tumors in the brain and spine. We’ll be opening a clinical trial very soon to see if it’ll also work on other diseases.
We’re also looking into how immunotherapy can work with radiation. After radiation, a tumor remains in the body as scar tissue and is slowly removed by the immune system. We’re exploring how to combine our treatments with immunotherapy drugs to trigger the immune system to fight tumors. We hope to start enrolling patients in our clinical trials soon.
Request an appointment at MD Anderson online or by calling 1-877-632-6789.
As a radiation oncologist at MD Anderson in The Woodlands, I get a lot of questions from my patients about how radiation therapy will affect them, what side effects they can expect and whether the treatment is safe.
Here are my answers to some of their frequently asked questions.
Do I need to bring someone with me for each treatment?
Unless you feel ill, you can typically drive yourself to treatment. In fact, many patients are able to work full-time during their treatment.
When will I start experiencing side effects?
Side effects depend on where you receive the radiation therapy, the dose given, whether you also receive chemotherapy and, if so, how much and what type. They usually begin by the second or third week of treatment and may last for several weeks after the final radiation treatment. In rare instances, there are serious side effects. Ask your doctor about the specific side effects that you may encounter and any follow-up questions about how to deal with them.
Will I lose my hair?
While chemotherapy causes hair loss throughout the body, that’s not the case for radiation therapy. Hair loss is associated with the radiation beam entrance and exit areas. Hair loss can be seen with radiation to the brain, head and neck, as well as the lower pelvis. Hair loss caused by radiation therapy may be temporary or permanent. At lower doses, hair loss is often temporary; at higher doses, hair loss can be permanent.
Am I radioactive?
You’re radioactive only if you’re undergoing treatment with a radiation seed implant. If you are hospitalized for this procedure, you’ll be in a protected room to limit your exposure to other people. This is something your doctor will talk to you beforehand.
Will I glow in the dark?
No. Even with permanent radiative seed implants, patients do not glow.
Will I set off airport security alarms after radiation treatment?
Can I be around children and pregnant women?
Yes -- unless you have just received a permanent radioactive seed implant. If that’s the case, you’ll only have the implant for a few days and should discuss this with your doctor.
Will I get a different cancer in the area where I’m receiving radiation?
The risk of developing a second cancer due to radiation therapy is very low. The benefits of your recommended treatment far outweigh the small risk that your radiation treatment could cause another cancer later in life.
Can I receive radiation in the same area if I have a cancer recurrence or secondary cancer?
With our newer technologies, we are able to carefully re-irradiate the same area in some situations. This is something you should discuss with your doctor.
Will I feel the radiation treatment?
No, radiation therapy uses high-energy waves, like those used with an X-ray. They are invisible and painless.
Am I more susceptible to infection with radiation?
Generally, cancer patients who are treated with radiation therapy alone aren’t more likely to develop infections.
Request an appointment at MD Anderson online or by calling 1-877-632-6789.