QUESTION: How is external radiation therapy planned?
ANSWER: For external radiation therapy to work, we first need to do a “planning session” or a “simulation.” During this session, we use a CT scan, and possibly also an MRI or PET-CT scan, to take pictures of your anatomy. We then work with a team of experts to build 3 dimensional computer models based on these scans. The 3 dimensional computer models are created based on your cancer and the normal organs that surround or are next to the cancer (which we want to avoid). The radiation beam is generated inside of a special device called a linear accelerator, or a LINAC. Part of the LINAC will rotate around you during the treatment. Hundreds of very small x-ray beams will all converge at and around the cancer. You can imagine that these x-ray beams are like “flashlights” that we converge onto the tumor from different directions. This is also similar to how a magnifying glass can focus light, but the light cannot be seen by the eye, and the light is coming from 360 degrees around the tumor.
Your anatomy is unique, and it takes our team about 1-2 weeks to plan how to best design the treatment for your particular cancer. After we are finished the planning, you will be ready to start.
QUESTION: What does external radiation therapy feel like?
ANSWER: You cannot feel radiation. Radiation therapy is like getting a chest x-ray, but directed at the tumor. You are awake during the procedure. You don’t see anything. You don’t feel anything. Nothing is “burned” – contrary to what you may see in the movies. You will not glow after the treatment. You will not lose the hair on your head, unless the treatment is directed toward the brain. You will not be radioactive. You will not be a danger to anyone. You cannot get “radiation poisoning.” You will not set off alarms or bells in the airport.
Side effects from external radiation therapy depend upon the location of the treatment and the dose of radiation. The side effects of external radiation depend on the normal organs that are near the tumor. You should talk to your doctor about what side effects to expect after your treatment, and how you manage them.
QUESTION: How long does one treatment take?
ANSWER: One treatment (called a “fraction”) takes about 1 hour, from the time you get to our building, get set up, get your treatment, and exit the hospital. The actual treatment time is usually less than 5 minutes.
QUESTION: How do we know how long to treat you?
ANSWER: The length of treatment depends upon the total dose of radiation delivered and the dose per fraction. You can think of the total dose of external radiation like a brick wall. We know how “big” the wall has to be in order to stop the cancer cells. The next question is, “how big do we make the bricks?” For many cancers, we make the bricks very small, because this has been shown to reduce side effects while still being able to stop the cancer cells. Thus, many patients are treated once a day, five days per week, for about five to eight weeks.
In certain cancers (for example prostate, breast, lung), we have been able to make the bricks larger. Thus, some patients may be treated for just a few weeks.
QUESTION: What comes out of the radiation machine (or LINAC)?
ANSWER: With external radiation, the energy used is either x-rays or protons. The x-rays are similar to what is used in a chest x-ray or CT scan, only more powerful.
Protons are also available at certain hospitals for certain cancers (specifically, for pediatric cancers). For most adult cancers, protons are currently experimental and only used in specific situations.
QUESTION: How do you know you are hitting the tumor with external radiation?
ANSWER:
Typically, we take x-ray pictures weekly or daily to help us direct the radiation. This is called image guidance. Sometimes, before starting radiation therapy for certain cancers we will refer you to another doctor to have small “seeds” or markers placed inside of the tumor that we can see on our scans when we deliver the treatment. The seeds are placed frequently for patients receiving radiation to the prostate, lung, or liver. The seeds will stay inside of you permanently. Please note that these seeds are different than the seeds that actually deliver radiation, as we will talk about in a bit.
QUESTION: Can you see the tumor dying?
ANSWER: Once you start receiving external radiation therapy, the radiation therapy is like putting money into an investment account: we don’t see anything after weeks or sometimes even months. The radiation effects occur over many months even after the treatment is complete. Thus, we cannot see tumors dying during treatment, and we don’t take any pictures to check. We will tell you what tests to get after you finish the treatment.
QUESTION: May I continue sexual activity during or after external radiation therapy? Will my partner be radioactive?
ANSWER: In general, for most cancers, you may continue sexual activity, though you should talk to your doctor for more details. Neither you nor your partner will be radioactive. However, you should not try to conceive before or during radiation therapy, as radiation is harmful to the fetus.