Host: The Japan Radiation Research Society
Clinical use of intensity modulation radiation therapy (IMRT/IMXT/IMPT) is increasing year by year. In U.S.A., 60% of the cancer patients take radiation therapy, and more than 70% radiation therapy are by IMRT. In Japan, the number of patient taking radiation therapy is around 20% of all the cancer patient, and only 30 hospitals are ready to support IMRT (2004 investigation). IMRT is to modulate an intensity of radiation field, which is generally uniform intensity, depending on the geometrical positions of target and the organ at risk. Thus IMRT allows dose to be concentrated in the tumor volume while sparing OARs.
As well as U.S.A., that IMRT becomes the one of the mainstream of the future radiation therapy in this country is expected.
A whole body radiation exposure by the leakage radiation with the irradiation MU value increase and a normal tissue exposure with lower radiation dose near the target is often considered as a problem in IMRT and it may relate to possibility of the secondary malignancy incidence increase more. IMRT is potentially used for a curative case with radiation therapy and many patients treated by IMRT will get longer surviving period without serious acute toxicities. IMRT also represents a special case for children, who are more sensitive to radiation-induced malignancy and have so small body to receive scattered radiation. The late incidence of the secondary malignancy could not be ignored if a patient will survive longer.
