Some people with cancer may hesitate to receive radiation therapy because they are uncertain about the treatment and the possible side effects. Your health care team can help you understand the treatment and answer any questions you may have. The following are answers to common questions about radiation therapy.

Q: What are the uses of radiation for cancer?

A: In addition to actively treating the tumor and its growth with the goal of a long-term cure, radiation therapy can be used to shrink tumors and reduce pressure, pain, and other symptoms of cancer in cases when it is not possible to completely eliminate the disease. This is called palliative radiation therapy, in which the goal is to improve a person's quality of life.

Q: Is it true that radiation cannot be controlled because it's invisible?

A: Although radiation is invisible, your radiation oncology team can control it using treatment machines. Doctors have been safely and effectively treating patients with radiation therapy for more than 100 years.

Q: Will radiation therapy cause another cancer?

A: Undergoing radiation therapy slightly increases the risk of developing a second cancer. However, it is important to remember that, for many people, radiation therapy can eliminate the cancer. This benefit far outweighs the risk that the treatment could cause a cancer later in life.

Q: Does radiation therapy harm surrounding organs?

A: The amount of damage done to the surrounding areas of the body depends on the type and location of the radiation. For example, men with prostate cancer who receive radiation therapy to the prostate may experience bowel or bladder problems because these organs are all close to each other. As much as possible, the radiation is aimed precisely at the tumor and the nearby tissues to avoid harming the surrounding organs. Talk with your doctor to learn what parts of your body will be affected by the radiation therapy.

Q: Is radiation therapy painful?

A: Most people cannot feel radiation from the machine, even during daily treatments; a few report a slight warming or tingling sensation in the area being targeted. Learn more about what to expect during radiation therapy.

Q: Do all patients experience the same side effects of radiation therapy?

For some people, radiation therapy causes few or no side effects. For others, the side effects are more severe. The reactions often begin by the second or third week of treatment and may last for several weeks after the final radiation treatment. Your radiation therapy health care team will work with you to ease or prevent many of these side effects. Learn more about side effects of radiation therapy.

Q: Does radiation therapy cause infertility?

Radiation therapy to the pelvic region can affect the reproductive system. For some women, permanent infertility (the inability to conceive a child or maintain a pregnancy) can occur, generally only if both ovaries receive radiation. Men receiving radiation therapy to the testes or to nearby organs, such as the prostate, will have lowered sperm counts and reduced sperm activity that affects fertility (the ability to father a child). Learn more about fertility and cancer treatment.

Q: Does radiation treatment make a person lose his or her hair?

A: Radiation therapy is a local treatment, meaning it only affects the area of the body where the tumor is located. People do not lose their hair from having radiation therapy, unless it targets a part of the body that grows hair, such as the scalp.

Q: Should a person having radiation therapy avoid physical contact with friends and family because of possible radioactivity?

A: External-beam radiation therapy does not make a person radioactive at any time. The radiation is delivered to the body, and there is no lingering radiation once the treatment machine is turned off. However, with internal radiation therapy (also called brachytherapy), the implants deliver most of the radiation to the surrounding areas, but some radiation can be emitted (sent) from the patient’s body. Thus, patients who receive internal radiation therapy will need to take certain precautions for a period of time to reduce others’ exposure to the radiation. Learn more about types of radiation and safety precautions.

Q: Is it true radiation is always used with chemotherapy and/or surgery?

A: Although some types of cancer respond best to combination treatment approaches—which may include radiation plus surgery, chemotherapy, or immunotherapy—radiation therapy alone can be an effective treatment for some cancers.

More Information

Understanding Radiation Therapy

Radiation Therapy: What to Expect

Side Effects of Radiation Therapy

Additional resources

National Cancer Institute: Questions and Answers About Radiation Therapy for Cancer

Last Updated: July 12, 2010