Multivariate Analysis And Prediction Of Radiation-induced Late Rectal Injury In Cervical Cancer

Object: To study retrospectively the association between endoscopic and radiation-induced late rectal injury(RLRI)in cervix cancer patients treated with IMRT including CT-based brachytherapy,and construct prediction models,to provide support for reducing the risk of RLRI and providing individual treatment for RLRI patients.Method: The clinical and DVH parameters of 189 cervical cancer patients were collected,including rectoscopic resulsts of 111 RLRI patients whose RTOG grade≥1.Side effects were assessed by the Radiation Therapy Oncology Group scale.Rectoscopic were assessed by Vienna Rectoscopy Score(VRS).1.Show the occurrence of RLRI by clinical follow-up;2.The association between dosimetric/clinical parameters with the risk of ≥grade 2 RLRI was screened by univariate and multivariate logistic regression analysis,The receiver operating characteristic(ROC)curve was used to determine the high-risk threshold for the occurrence of≥grade 2 RLRI;3.The association between dosimetric/clinical parameters with the risk of VAS≥3 was screened by univariate and multivariate logistic regression analysis,and a prediction model was established.The differentiation and calibration of the model were evaluated by the ROC curve and Hosmer-Lemeshow test;4.Coherence between RTOG and VAS was determined by Fisher’s exact test and Spearman Rank Correlation Analysis.Results:1.Median follow-up was 27 months.The occurrence rate of ≥grade2 RLRI was 30.7%(58/189)and grade 3-4 RLRI was 4.8%(9/189).The occurrence rate of VAS≥3 was 36.9%(41/111)in RLRI patients;2.Univariate analysis showed that HRCTV volume,the prescri bed doses of EBRT and BT,rectum V35,V40,V45,V50,Dmax,D mean,D0.1cc,D1cc,D2cc,D5cc and D10cc were significantly corr elated with the occurrence of ≥grade 2 RLRI;Multivariate analysis showed that D2cc was the independent risk factor for ≥grade 2 RL-RI(P<0.05),and the high-risk threshold values was 81.36Gy;3.Univariate analysis showed that FIGO stage,HRCTV volume,rectum V25,D0.1cc,D1cc,D2cc,D5cc and D10cc were significantly correlated with the occurrence of VAS≥3;Multivariate analysis showed that FIGO stage,D0.1cc,D1cc and D2cc were the independent risk factors for VAS≥3(P<0.05).The AUC of ROC curves combined with D0.1cc,D1cc and D2cc is 0.756,Hosmer-Lemeshow χ~2 was1.493(P=0.993),the prediction model with a favorable predictive efficacy;4.The correlation between RTOG and VAS,with significant coherence(P<0.05).The Spearman rank correlation was 0.7(P<0.05).Conclusion: DVH parameters could predict the incidence of ≥grade2 RLRI and radiation-induced mucosal changes,D0.1cc,D1cc,and D2cc of the rectum should be limited to an appropriate range when evaluating a radiotherapy plan;RTOG and VAS can be combined for the assessment of RLRI;This study provides a basis for the prediction and individualized treatment of RLRI.