Radiosensitizers are drugs that make cancer cells more sensitive to radiation therapy. Radiation therapy is one form of cancer treatment that prevents malignant cells from growing and dividing. Radiation treatments, however, can also damage normal cells. As a result, researchers are studying substances that can either make a tumor more sensitive to radiation without affecting healthy tissues, or that can shield normal cells from radiation.

Also known as hypoxic radiosensitizers, these drugs change the way cells respond to radiation. Radiosensitizers work to increase the normally low levels of oxygen found in cancer cells. Cancer cells that have normal or higher levels of oxygen are more receptive to radiation treatment. Radiosensitizers also make it more difficult for the cancer cells to repair themselves, and as a result, they die.

Another group of chemicals used to modify a cell’s response to radiation are radioprotectors. Also known as radioprotectants, these drugs protect normal cells while exposing cancer cells during radiation therapy.

As of 2007, the U.S. Food and Drug Administration (FDA) has not approved of any drugs for use as radiosensitizers. However, certain chemotherapy drugs already approved for cancer treatment are being studied for use as radiosensitizers. These include topotecan hydrochloride, paclitaxel and cisplatin. In addition, scientists are studying various drug compounds not yet approved or proven for the general patient population for use as radiosensitizers. Treatment with radiosensitizers is only available through clinical trials and patients must be approved by physicians to enroll in the study.