What is a Radiosensitizer and How Is It Used in Radiation Therapy?


A radiosensitizer, or a radiosensitizing agent, is a drug that makes cancer cells more vulnerable to radiation therapy. Radiation therapy uses high-energy radiation to shrink tumors by disrupting the DNA of cancer cells, causing them to die. Radiosensitizers can be drugs that kill or inhibit growth of cancer cells, like chemotherapy, or drugs that only kill cancer cells when combined with radiation, says David Kozono, MD, PhD, radiation oncologist at Dana-Farber/Brigham and Women’s Cancer Center.

How is a radiosensitizer used in cancer treatment?

Radiation oncologists like Kozono carefully direct beams of radiation to target and treat tumors almost anywhere within your body. But despite this cautious, specific placement of radiation, healthy tissue surrounding the tumor may still be exposed to levels of radiation that can cause both short and long-term side effects. Radiosensitizers, administered at the time of radiation therapy, can mitigate these side effects. By enhancing the effectiveness of radiation therapy, they can lower the amount of radiation necessary to treat tumors.

What are the side effects?

Side effects associated with radiosensitizers vary in severity and duration. Short-term side effects such as changes in the skin, and fatigue are more common than long-term side effects, such as hormonal changes or in rare cases, secondary cancers. Long-term side effects can take years to develop, if at all.

Side effects depend on several factors, including dosages of drugs and radiation, location of the tumor, types of drugs being administered, and the size of the area being treated. It’s important to speak with your care team about any side effects you may be experiencing, as your doctors can recommend medications or therapies to alleviate these issues.

Are there particular types of cancer that respond better to a radiosensitizer? 

Some types of cancer, like lymphoma, respond to low enough doses of radiation therapy that radiosensitizers may not necessary, says Kozono. In contrast, cancers that are more resistant to radiation, such as lung, pancreatic and brain cancer, may still be treated successfully with radiation therapy, often with the help of radiosensitizers to increase the radiation’s effectiveness. Every patient’s case is unique and therefore carefully examined to determine whether radiation therapy – with or without a radiosensitizer – is the best course for treatment.

Learn more about radiation therapy from Dana-Farber’s Department of Radiation Oncology.

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