This invention, with cancer radiotherapy it jointly uses be able to decrease the radiation dose, the radiotherapy reinforcement medicine which can lighten also the side effect it regards. (A) tegahuru and (B) the radiotherapy reinforcement medicine which contains gimerashiru.本発明は、癌放射線療法と併用して放射線量を低減でき、副作用も軽減できる放射線治療増強剤に関する。(A)テガフール及び(B)ギメラシルを含有する放射線治療増強剤。