How Long Does Radiation Stay in Your Body After Treatment?

Along with surgery and chemotherapy, radiation therapy has long been a mainstay of cancer treatment. It uses high-energy waves or particles such as x-rays, gamma rays, electrons, or protons to destroy or damage tumor cells. Radiation creates small breaks within the DNA of cancer cells, preventing the cells from growing and dividing, and often causing them to die.

radiation therapy, radiation oncology
Radiation therapy uses high-enegery waves or particles to destroy or damage tumor cells.

Because cancer cells divide rapidly, they’re more likely to succumb to DNA damage, but radiation can damage DNA in normal cells as well. The damage that radiation therapy does to normal cells may lead to a variety of side effects, which generally improve over time. These can include fatigue, red or irritated skin the treatment area, and, in rare cases, low white blood cell or platelet counts.

External radiation therapy – a form of treatment that uses a machine to beam high-energy rays into a tumor – affects cells for only a few seconds. The beams pass quickly through the body and are absorbed by special shields positioned around the patient.

Some cancers are treated with internal radiation therapy, in which radioactive material, sealed in a container, is implanted next to or inside a tumor. High doses of internal radiation therapy are given by placing a powerful source of radioactivity in the body for a few minutes at a time. Lower doses are delivered with implants that remain in the body longer, often a few days. In a treatment known as brachytherapy, doctors implant small radioactive pellets, or “seeds,” that emit radiation for a few weeks or months but remain in the body permanently.

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Internal radiation therapy can cause the body to give off small amounts of radiation for a short period of time. Patients who receive temporary implants often stay in the hospital while the implant is in place and may have limitations on visitors. Their bodily fluids are not radioactive. Once the implant is removed, their body is radiation-free.

Patients with permanent implants give off small doses of radiation as long as the radiation source is active – usually a few weeks or months. As with patients receiving temporary implants, the body fluids and personal items of patients with permanent implants are not radioactive. Because it is low-level, the radiation usually doesn’t travel much beyond the area being treated, so there’s little chance of exposing others to radiation. Still, to be on the safe side, patients may be advised to limit contact with small children and pregnant women.