RESUMO
Objective To identify dosimetric predictors for the development of gastrointestinal toxicity in patients with pancreatic adenocarcinoma treated with TOMO radiotherapy .Methods From January 2014 to Janu-ary 2015 ,we analysed the medical records of 68 pancreatic cancer patients who received helical tomotherapy from Air Force General Hospital .The stomach and duodenum were contoured separately to determine their dose volume histogram(DVH)parameters.Chi-square test was employed to analyze the count data .Spearman correlation anal-ysis was used to analyze the relationship between occurrence of gastrointestinal toxicity and clinical and physical factors.Logistic regression models was performed to identify risk factors associated with gastrointestinal toxicity . Results The median follow-up was 9 months(4~16 months).18 patients experienced grade II acute gastroin-testinal toxicity ,1 patient experienced grade Ⅲ acute gastrointestinal toxicity , whereas 17 patients experienced grade II late gastrointestinal toxicity ,1 patient experienced grade Ⅲlate gastrointestinal toxicity .On UVA,the vol-ume,Dmean,D1,D3,D5,D10,V5 to V40,and V5′to V45′of duodenum were significantly associated with GradeⅡor higher gastrointestinal toxicity ( P <0.05 ) .The MVA, V45′of duodenum was independent predictor for gradeⅡor higher gastrointestinal toxicity(P<0.05).The ROC analysis also showed that V45′of 0.5cm3 was the optimal threshold to predict for gastrointestinal toxicity for the entire cohort .Conclusion V45′of duodenum is of greater importance in the judgment of occurrence of hypofractioned radiation -induced gastrointestinal toxici-ty.