Dosimetric Analysis Of Simultaneously Integrated Boost (SIB) Technique For Breast-conserving Radiotherapy

Objective:To compare the target coverage and normal tissue dose with the simultaneously integrated boost (SIB)and the sequential boost(SBT) technique in early stage breast cancer. Methods:Ten patients with breast cancer treated by conserving breast operation were selected to study, the region marked by silver clips with extended margin of 1.5～2.0cm was defined as gross target volume (CTVTb) and the whole breast was delineated as the clinical target volume (CTV). The breast and boost planning target volumes (CTV and CTV-n,s) were treated simultaneously (i.e., for breast and boost target volumes received 1.81 Gyx28 and 2.15 Gyx28 dose respectively). Dose-volume histograms of the CTV and CTVTbS and organs at risk with the SIB technique were compared with those for the sequential boost technique,2.0 Gy×25+2.0Gyx5。Results: There were not significant difference for dose uniformity and conformality for clinical target volume (CTV),but CTVTb were different between the plannings with SIB and the sequential boost technique(P=0.019). There were not significant difference for the volumes of the ipsilateral lung received equal or more than the mean dose between different planning, but the volume of the lung received>20 Gy in sequential boost planning was significantly higher than that in SIB planning(P=0.001). There were not significant difference for the volumes of the heart received≥30 Gy and equal or more than mean dose in two planning.Conclusions:There is not significant difference for most of the dosimetric parameters in simultaneously integrated boost (SIB)and the sequential boost planning, but the volume of the ipsilateral lung received≥20 Gy in sequential boost planning was significantly higher than that in SIB planning and uniformity and conformality for gross target volume (CTVTb) in SIB superior to in sequential boost planning. The SIB technique is proposed for standard use in breast-conserving radiotherapy because of its dose-limiting capabilities, easy implementation, reduced number of treatment fractions.