Factors associated with set-up errors in intensity-modulated radiotherapy after breast conserving surgery / 中华放射医学与防护杂志

ABSTRACT

Objective To evaluate the difference of set-up errors between thermoplastic mask and breast bracket in patients receiving intensity-modulated radiotherapy after breast conserving surgery,and the impact of clinical factors associated with set-up errors.Methods A total of 34 patients treated with intensity-modulated radiotherapy after breast conserving surgery from January 2016 to June 2018 were reviewed.Eighteen patients were fixed with thermoplastic mask,and sixteen were with breast bracket.Weekly CBCT scan records were used to analyze set-up errors,and group systematic and random errors were computed.The influence of clinical factors on set-up errors was also analyzed.Results The immobilization technique with thermoplastic mask showed great superior in comparison with breast bracket;however,only in the Ty(translation) and Ry(rotation),the differences had significance.Based on group systematic and random errors,PTV margins in Tx,Ty and Tzwere 2.65,4.36 and 2.87 mm in thermoplastic mask group,as well as 5.71,6.07 and 4.20 mm in breast bracket group,respectively.Multi-factor regression analysis showed that BMI was independent factors affecting set-up errors.Conclusions Compared with breast bracket,the immobilization technique with thermoplastic mask has the potential of reducing set-up errors and PTV margins in patients receiving intensity-modulated radiotherapy after breast conserving surgery,especially in patients with high BMI.