[The role of radiation therapy for rectal cancer: recent trend].

In Japan, preoperative chemoradiotherapy has not been routinely used for operable locally-advanced rectal cancer, mainly because of the chronic toxicities for intestines and the anal functions. Recently, by the use of intensity-modulated radiation therapy (IMRT), one can concentrate radiation doses to the target volume whereas minimizing the unnecessary doses to the surrounded normal tissues. Especially, IMRT seems promising in reducing the acute and late toxicities to intestines. With the use of IMRT as a part of the preoperative chemoradiotherapy would be promising by increasing the intensity of the treatment. Besides IMRT, particle therapies such as carbon ions are also considered promising. Furthermore, stereotactic body radiation therapy, intraoperative radiation therapy, combined use of molecular targeted agents and hypoxic cell radiosensitizers, might be promising.