Answers to Common Questions about Radiation Safety

By Andrea Peirce

on Thursday, April 3, 2014

Pictured: Alice Ho Memorial Sloan Kettering has helped to set nationwide safety standards for radiation therapy to destroy cancerous tissue.

Memorial Sloan Kettering Radiation Safety Officer Jean St. Germain answers common questions about the safety of adults undergoing radiation treatment for cancer.

Radiation treatment is one of the most common and effective ways to destroy cancer cells and shrink tumors. It works by exposing targeted areas to high-energy rays or waves in such a way that the structure of cells is damaged or destroyed.

At Memorial Sloan Kettering, approximately half of our adult cancer patients undergo radiation therapy as a form of primary treatment or as part of a broader approach that includes chemotherapy, surgery, or other modalities. For many cancers, radiation treatment may be all that is needed to eliminate disease.

There are different ways to deliver radiation treatment. With external beam radiation therapy, treatment is delivered from a machine outside the body. With internal radiation (brachytherapy), sealed sources of radioactivity are placed near or within the tumor. Less commonly, radiation treatment can also be administered using liquid materials by mouth or infusion through a vein (systemic radiation).

Although it has been a widely used treatment for decades, confusion and misunderstandings about the safety of radiation treatment persist. We asked Memorial Sloan Kettering Radiation Safety Officer Jean St. Germain to tell us about the concerns she hears most frequently from patients and their families — and what answers and reassurance she provides.

Does receiving external-beam radiation make a person radioactive or able to expose others to radiation?

External-beam therapy does not make a person radioactive in any way. The therapy only affects your cells for the very short time that you are receiving treatment. A person who has received external-beam radiation is unable to contaminate or transfer that radiation to any other person.

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How can I be sure that the external-beam radiation machine isn’t damaging normal, healthy tissue in my body?

We have carefully developed methods for calibrating radiation beams and ensuring that they reach the areas they are intended to target. Even when normal tissues near the area undergoing radiation receive small amounts of radiation, it is rare for long-term damage to occur. Our doctors also know how much radiation healthy tissue can receive without causing irreversible damage. We often use special masks, molds, or casts of body parts to keep you absolutely still during treatment, so that we can aim the radiation beams precisely to the area we want to treat.

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Is there any risk that internal radiation implants (brachytherapy) will leak or break free from where they are placed and move around my body?

With brachytherapy, we use a needle or a catheter to insert radioactive material contained within an impenetrable sealed source such as a seed, pellet, wire, or capsule. As the radioactive isotopes inside the implant decay naturally over time, they emit radiation and damage nearby cancer cells. This radioactivity travels only a certain distance beyond the implant, and eventually deteriorates to the point that the implant no longer gives off any radiation. The implants are specially tested and sealed to ensure that radioactive material doesn’t leak, and we place them in such a way that it’s highly unlikely they will move. Also, in the case of brachytherapy for genitourinary cancers, while there is no risk that the implants will come out with semen, we do give patients a strainer to use for 24 to 48 hours after the procedure when urinating, in the rare case that a seed becomes dislodged.

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Should I limit contact with anyone while brachytherapy implants are inside my body?

Most of our safety concerns are related to being in physical contact with children for extended periods of time, since their bodies are undergoing such rapid change and growth and are therefore more vulnerable to abnormal cell changes. Because we vary the radiation dose in each implant as well as the number of implants we insert based on your particular cancer, we provide you with specific advice about precautions to take when you’re in close contact with children.

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Do prostate seed implants put my sexual partner or the person I sleep next to at risk in any way?

Prostate seeds are sealed sources. You cannot contaminate another person by being in his or her physical vicinity, during sexual intercourse, or through any other form of intimate contact. Your doctor or a member of the radiation safety staff will discuss any special precautions you should take with sleep arrangements before you leave the hospital. For example, based on such factors as your age and the age of your partner, for a period of time we may ask that you avoid embracing your partner from the back in the “spooning“ position through the night.

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Do I pose a danger to others after receiving radioactive iodine therapy for thyroid cancer?

For several days following this therapy, radioactive substances can be emitted through body fluids such as saliva, urine, and sweat. We send patients home with detailed instructions on how to care for themselves for the first few days — from limiting contact with young children and pets to using separate utensils and towels.

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I am having an imaging test using radioactive materials. Will I be radioactive after the test?

Radioactive material will stay in your body for several hours or days depending on the type used and the metabolism of the compound to which it was attached. Eventually, the material decays and your body naturally flushes it out through urine, sweat, and other forms of biological elimination. We make sure the specifics are clear to you before the test, and we may also issue an information card explaining your treatment in the event that you are questioned by someone in airport security, for example.

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no one ever told me when I had radiation 8 years ago that I could develop an Angiosarcoma...So it's a big surprise that I now have a full blown sarcoma.

Following Brachytherapy and beam radiation is there a limit to the amount of radiation to a particular site?
If further cancer develops in the bone area already treated can further radiation be used to quell or kill the cancer?
What is the outcome of too much radiation to a bone or soft tissue site?
Are there further options in such circumstances?
Thanks for your help.

Roger, thanks for reaching out! There are no specific regulatory limits on the amount of radiation to a particular site during treatment when that treatment has been deemed appropriate and justified by your doctor. Our doctors follows appropriateness criteria and accepted professional guidance, along with best procedures based on the latest research to deliver appropriate treatments. They always seek to target the most effective dose of radiation directly at the cancer, while minimizing radiation to the healthy parts of a patient's body. Decisions about the best therapy and best technology are based on each individual case. Also, different tissues have a different sensitivity and response to various types of radiation. Each case is unique.

Unfortunately we can't answer personal medical questions on our blog. But if you or someone you care for has had radiation to the bone and you are wondering about treatment options, we encourage you to consult with one of our specialists. Please call our Physician Referral Service at 800-525-2225.

Radiation caused damages to chromosomes.Will long term Radiotherapy treatment cause permanent chromosomal damages leading to gene mutation?

I too am interested in the damage to chromosomes leading to gene mutation.
Since radiation three years ago I have developed MDS. Is there a possible link?

Thank you for writing, Carol! Unfortunately we cannot answer personal medical questions on our blog. If you would like to make an appointment for a consultation with one of our specialists who can provide a personalized assessment of your treatment options, please call our Physician Referral Service at 800-525-2225.

It is stated above, "it is rare for long term damage to occur." Are the studies available to confirm this? i.e. breast radiation - 10 years later, lung or respiratory damage?

Lana, we sent your question to Beryl McCormick, Chief of our External Beam Radiotherapy Service, who responded that there have been several studies of the long-term effects of breast radiation. Two of the largest were reported in the New England Journal of Medicine in 2002
( and in the Lancet Oncology in 2005 ( She noted that this area has been studied with much longer follow-up than some of the newer chemotherapy regimens. Thank you for your comment.

Are there any allergic reactions caused by the radioactive material used during a CT scan or a PET scan such as Itching and a soft red rash?

Joe, radioactive materials are not used during regular CT scans, but they are used during PET scans and PET/CT scans. It's possible to have an allergic reaction to the tracer. If you think you have had an allergic reaction, we recommend that you discuss this with your doctor. Thank you for your comment.

Are you allowed to go swimming after radiation treatment

Eileen, radiation treatment can cause sensitivity of the skin, so this is something you should discuss with your doctor. Thank you for your comment.

As a caregiver, what precautionary safety measures do i take when one of my clients start radiation treatments for 7 weeks, 5 days a week?

External-beam therapy does not make a person radioactive in any way. The therapy only affects your cells for the very short time that you are receiving treatment. A person who has received external-beam radiation is unable to contaminate or transfer that radiation to any other person. Thank you for your comment.

I have had a full hysterectomy and was classified as stage one. Soon I will be receiving brachytherapy to my vaginal cuff. How long is the possible risk of radiation exposure to my young grandchildren and others? I don't want to be treated as a leper but also don't want to harm others in even the slightest way.

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We welcome your questions and comments. While we share many of them with our world-class doctors and researchers, we regret that in order to protect your privacy, we are not able to make personal medical recommendations on this forum, nor do we publish comments that contain your personal information. If you would like to consult with an MSK doctor, we encourage you to make an appointment at 800-525-2225 or request an appointment online.

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