RB1 and cancer: Based on the high conformity of GKRS plans, which are usually comparable to the characteristics of IMRT plans, we assessed the risk of secondary cancers in the irradiation zone as extremely low, taking into account other factors as well; firstly, radiation therapy was not carried out in children younger than one year - the most dangerous age in terms of the risk of radiation-induced tumors development [10], and secondly, only seven children had Rb1 gene mutation.