Abstract: Provided is an a combination therapy including a radiosensitizing agent and radiation, and being effective to inhibit proliferation of cancer stem cells. Further provided is a combination which includes a radiosensitizing agent and radiation, and effectively reduces incidence of at least one of cancer relapse and metastatic cancer in a subject having a cancer, wherein the cancer includes cancer stem cells. Also provided are anthraquinone derivatives for use as radiosensitizing agents in combination with radiations, the combination therapy being cancer specific. Further, the radiosensitizing agents were found to be cancer specific, namely, some being more effective against a cancer type as compared to others.