In clinical radiotherapy (RT), there is always simultaneous exposure of normal and cancer-bearing cells. Radiation oncologist tries to minimize normal tissue exposure and at the same time maximize dose to the tumor-bearing tissue. Despite advances in RT equipment and treatment techniques, inevitably some normal tissues will be irradiated leading to toxicity. Although most of the toxicities are manageable, in some clinical situation, the side-effects could be life-long and irreparable causing prolonged suffering, cosmetic deficiencies, and tremendous psychological trauma [1]. The risk of late effects on normal tissue (LENT) and radiation-induced second malignancy (RISM) ranges from 5% to 10% and 2% to 10% respectively in adults treated with curative RT [2]. Addition of radiosensitizers and chemotherapy drugs during radiation improve survival however increases acute toxicities significantly [3]. Modern cancer immunotherapy incorporated in RT to increase immune-mediated cell kill could also increase end organ toxicities [4]. Modern radiation techniques, namely, altered fractionation and flash RT, too increase toxicities further [5]. Heavy ion and proton beam therapy promise to limit complications in CNS tumors in children, but acute complications are similar like photon beam therapy.