Predictive Value Of Primary Gross Tumor Volume Measured By MRI In Response To Neoadjuvant Chemoradiotherapy In Locally Advanced Rectal Cancer

Objective:To evaluate whether primary gross tumour volume(p GTV)can predict the tumorregression of locally advanced rectal cancer(LARC)after neoadjuvant chemoradiotherapy(n CRT),identify clinical predictors of tumor regression,and analyze the roles of p GTV,clinical features and prognostic factors in predicting disease free survival(DFS)and overall survival(OS).Methods and Materials:In a retrospective analysis of LARC data for patients who underwent n CRT and Total Mesorectal Excision(TME)with definitive pathological diagnosis between2014 and 2018,a total of 123 patients were included.The p GTVof LARC was measured by magnetic resonance imaging(MRI),and the independent predictors of tumor regression after n CRT were determined by statistical analysis.The Area Under Curve(AUC)of p GTV was calculated by Receiver Operating Characteristic(ROC)Curve,which was also used to determine the optimal cut-off value(CUT-OFF value).Cox proportional hazards regression model was used for univariate and multivariate analysis,including exploring the influence of related factors on DFS and OS.Spss21.0(IBM,Armonk,New York,USA)was used for statistical analysis,and P < 0.05(bilateral)was used as the test level.Results:123 patients were included in the study,including 18(14.63%)patients achieved pathological complete response(PCR),52(42.28%)in the better response group,71(57.72%)in the worse response group,88(71.54%)in extramural vascular invasion(EMVI),77(62.60%)in ypn0,29(23.58%)in ypn1 and 17 in ypn2(13.82%).Logistic regression analysis showed that smaller p GTV was an independent predictor of better tumor regression(P =0.001),and the optimal cut-off value of p GTV was 49.25 cm3 and AUC was 0.712(P < 0.001)between the better response group and the worse response group.The median follow-up time was 41 months,36 patients(29.27%)had recurrence or metastasis,and 18 patients(14.63%)died.Cox survival analysis showed that there was no statistical significance in DFS and OS between the better response group and the worse response group(P > 0.05),and tumor length and diameter(HR=1.198;P =0.042),EMVI(HR=3.386;P =0.023)were independent predictors of DFS,while age(HR=1.054;P=0.028),tumor length,diameter(HR=1.430;P =0.002)and yp N staging(HR=3.454;P=0.000)was significantly correlated with OS(P < 0.05).Conclusions:This study foundthat in LARC patients receiving n CRT,the p GTV measured based on MRI was significantly correlated with tumor regression,and tumor length and EMVI were independent predictors of DFS,while age,tumor length and ypN stage were independent predictors of OS.