MRI Predictive Factors for Tumor Response in Rectal Cancer Following Neoadjuvant Chemoradiation Therapy - Implications for Induction Chemotherapy?

Purpose Clinical and magnetic resonance imaging (MRI) characteristics at baseline and following chemoradiation therapy (CRT) most strongly associated with histopathologic were investigated and survival outcomes evaluated in accordance with imaging and pathological response. Methods and Materials Responders were defined as mrT3c/d-4 downstaged to ypT0-2 on pathology or low at risk mrT2 downstaged to ypT1 or T0. Multivariate logistic regression of baseline and posttreatment MRI: T, N, extramural venous invasion (EMVI), circumferential resection margin, craniocaudal length Results Two hundred eighty-one patients were eligible; 114 (41%) patients were pathology responders. Baseline MRI negative EMVI (odds ratio 2.94, P =.007), tumor height ≤5 cm (OR 1.96, P =.02), and mrEMVI status change (positive to negative) following CRT (OR 3.09, P P Conclusions Tumor height and mrEMVI status are more important than baseline size and stage of the tumor as predictors of to CRT. Both MRI- and pathologic-defined responders have significantly improved survival. Good response to CRT in locally advanced rectal cancer with ypT0-2 carries significantly better 3-year overall survival and disease-free survival. Use of induction chemotherapy for improving mrEMVI status and knowledge of MRI predictive factors could be taken into account in the pursuit of individualized neoadjuvant treatments for patients with rectal cancer.