Efaproxiral is primarily used as a radiosensitizer in cancer treatment. It enhances the effectiveness of radiation therapy by increasing the sensitivity of cancer cells to radiation. This is particularly beneficial in treating brain metastases and other solid tumors, where it helps improve the outcomes of radiation therapy. By modifying the oxygen-carrying capacity of hemoglobin, efaproxiral facilitates better oxygen delivery to hypoxic tumor cells, making them more susceptible to radiation damage. Its application is often studied in combination with whole-brain radiation therapy to improve survival rates and treatment efficacy in patients with advanced cancer.