Value Of Apparent Diffusion Coefficient In Assessing The Response To Preoperative Chemoradiotherapy With Simultaneous Integrated Boost For Locally Advanced Rectal Cancer

Objective:To investigate efficacy,and toxicities of the modality of regular preoperative intensity-modulated chemoradiotherapy with a simultaneous integrated boost?SIB-IMRT?or regular preoperative intensity-modulated chemoradiotherapy?IMRT?in locally advanced rectal cancer?LARC?,and to use apparent diffusion coefficient?ADC?evaluating the response to Simultaneous integrated boost intensity-modulated chemoradiotherapy.Methods:64 patients with LARC were recruited and divided into regular-arm and boots-arm with 32 cases each nonrandomly.Both arms assigned to receive preoperative IMRT?50Gy/25f?concurrent 2 cycles capecitabine?1650mg/m²/d,twice daily,d1-d14,d22-d35?;boots-arm assigned to receive a SIB to the rectal tumor and high-risk recurrence area up to a total dose of 56Gy.Surgery was performed 6-8 weeks after completion of preoperative therapy.Botharmswereprospectivelyenrolledpre-andpostoperative chemoradiotherapy rectal high-resolution MRI.The ADC values were measured on the sequence of diffusion-weighted imaging?DWI?,with b value of1000s/mm².Compared with the ypCR rate,tumor-downstaging?T-downstaging?rate,tumor regression grading?TRG?remission rate,sphincter preservation rate,effective rate and the changes of ADC related parameters between the arms.ROC curve was used to analyze the diagnostic efficacy of ADC related parameters in the evaluation of ypCR.Results:1.All patients completed preoperative chemoradiotherapy combined with surgery.There were no statistical significant differences in gender,age,TN stage,clinical stage,tumor location,pathological differentiation degree,clinical stage,preoperative CEA level between the two groups?P?29?0.05?.2.In boots-arm,ypCR rate was 28.13%?9/34?,T-downstaging rate was84.38%?21/32?,TRG remission rate was 59.38%?19/32?,sphincter preservation rate was 78.13%?25/32?,and effective rate was 75.00%?25/32?.In regular-arm,ypCR rate was 12.50%?4/32?,T-downstaging rate was 56.25%?18/32?,TRG remission rate was 34.38%?11/32?,sphincter preservation rate was 53.13%?17/32?,and effective rate was 40.63%?13/32?.The T-downstaging rate,TRG remission rate,sphincter preservation rate and effective rate of treatment in boots-arm were higher than those in regular-arm?P?27?0.05?.3.There were no statistical significant differences in acute side effects,incidence of surgical complications and R0 resection rate?P?29?0.05?.4.The ADC_pre,ADC_post,ADC_diffiff and ADC_ratioatio of boots-arm were?0.87±0.15??10^-3mm²/s,?1.44±0.22??10^-3mm²/s,?0.56±0.23??10^-3mm²/s,?0.68±0.37?,respectively.The ADC_pre,ADC_post,ADC_diffiff and ADC_ratioatio of regular-armwere?0.93±0.18??10^-3mm²/s,?1.33±0.23??10^-3mm²/s,?0.40±0.20??10^-3mm²/s,?0.45±0.24?,respectively.ADC_post,ADC_diffiff and ADC_ratioatio in the boots-arm were higher than those in regular-arm,there were statistical significant differences in the latter two?P?27?0.05?.5.The ADC_postost and ADC_diffiff values had the diagnostic potential of predicting and evaluating ypCR?P?27?0.05?.The optimal cutoff value for the identification of patients with ypCR was 1.34?10^-3mm²/s for ADC_post{during which its AUC was0.785[95%CI?0.699,0.901?],with 92.3%?12/13?sensitivity,58.8%?30/51?specificity,and 65.6%?42/64?accuracy,respectively},0.409?10^-3mm²/s for ADC_diff{during which its AUC was 0.722[95%CI?0.573,0.872?],with84.6%?11/13?sensitivity,52.9%?27/51?specificity,and59.3%?38/64?,respectively}.Conclutions:1.Compared with regular IMRT,SIB-IMRT had better short-term efficacy,higher ADC_diffiff and ADC_ratio,toxicity and side effects were acceptable,long-term survival benefits awaited further follow-up.2.ADC_postost and ADC_diffiff had potential to predict and evaluate ypCR after preoperative chemoradiotherapy in LARC.