Quantitative evaluation before and after treatment with MRI in patients receiving neoadjuvant chemoradiotherapy for rectal tumor and its correlation with pathology

OBJECTIVE. The purpose of this study was to determine whether quantitative T2-weighted imaging and apparent diffusion coefficient (ADC) texture features of local advanced rectal cancer are predictive of pathologic total regression after neoadjuvant chemoradiotherapy. MATERIALS AND METHODS. In this retrospective study, 44 patients (32 men, twelve women; median age, 57 years) were identified who underwent post neoadjuvant chemoradiotherapy MRI without intervening treatment from April 2015 through April 2019. Texture features of rectal cancer on T2-weighted and ADC images were extracted and compared between category pathologic total regression versus partial regression by means of student t test or Mann-Whitney U test. Multivariate logistic regression analysis was performed, and ROC curves were calculated. RESULTS. 22 of the 44 (50 %) patients were in complete responders, and 50 % (22/44) were in partial responders after neoadjuvant chemoradiotherapy. ADC change correlates with treatment response and a cut off 1310 x 10-6 mm2/sn predicts the pathologic total responds with a sensitivity of 72 % and a specificity of 77 %. Furthermore, CRT induced a significant decrease in all rT2wSI descriptives in complete responders. This drop was significantly larger than for incomplete response groups. Post CRT skewness change of rT2wSI in pathologic complete response group shows positive correlation with histopathologic TRG. CONCLUSION. In patients with locally advanced rectal cancer, change in post-CRT skewness of the T2 histogram and change in ADC were useful for predicting a favorable response to neoadjuvant CRT. KEY WORDS. Rectal cancer, neoadjuvant chemoradiotherapy, histogram analysis, relative T2 weighted images, ADC