Textural differences based on apparent diffusion coefficient maps for discriminating pT3 subclasses of rectal adenocarcinoma

BACKGROUND The accuracy of discriminating pT3a from pT3b-c rectal cancer using highresolution magnetic resonance imaging(MRI)remains unsatisfactory,although texture analysis(TA)could improve such discrimination.AIM To investigate the value of TA on apparent diffusion coefficient(ADC)maps in differentiating pT3a rectal adenocarcinomas from pT3b-c tumors.METHODS This was a case-control study of 59 patients with pT3 rectal adenocarcinoma,who underwent diffusion-weighted imaging(DWI)between October 2016 and December 2018.The inclusion criteria were:(1)Proven pT3 rectal adenocarcinoma;(2)Primary MRI including high-resolution T2-weighted image(T2WI)and DWI;and(3)Availability of pathological reports for surgical specimens.The exclusion criteria were:(1)Poor image quality;(2)Preoperative chemoradiation therapy;and(3)A different pathological type.First-order(ADC values,skewness,kurtosis,and uniformity)and second-order(energy,entropy,inertia,and correlation)texture features were derived from whole-lesion ADC maps.Receiver operating characteristic curves were used to determine the diagnostic value for pT3b-c tumors.RESULTS The final study population consisted of 59 patients(34 men and 25 women),with a median age of 66 years(range,41-85 years).Thirty patients had pT3a,24 had pT3b,and five had pT3c.Among the ADC first-order textural differences between pT3a and pT3b-c rectal adenocarcinomas,only skewness was significantly lower in the pT3a tumors than in pT3b-c tumors.Among the ADC second-order textural differences,energy and entropy were significantly different between pT3a and pT3b-c rectal adenocarcinomas.For differentiating pT3a rectal adenocarcinomas from pT3b-c tumors,the areas under the curves(AUCs)of skewness,energy,and entropy were 0.686,0.657,and 0.747,respectively.Logistic regression analysis of all three features yielded a greater AUC(0.775)in differentiating pT3a rectal adenocarcinomas from pT3b-c tumors(69.0%sensitivity and 83.3%specificity).CONCLUSION TA features derived from ADC maps might potentially differentiate pT3a rectal adenocarcinomas from pT3b-c tumors.