Quantitative MRI assessment of mucinous rectal adenocarcinoma to predict tumour response after neoadjuvant therapy

Abstract

To evaluate the association between volume ratio of the mucus pool and tumour response to neoadjuvant therapy in patients with mucinous rectal adenocarcinoma (MC). The volume of the mucus pool and whole tumour on pre-therapeutic T2-weighted magnetic resonance imaging (MRI) of 79 patients was measured using semi-automated software. Mucus pool volume, whole tumour volume, and volume ratio of the mucus pool were compared to tumour response and tumour and lymph node downstaging after neoadjuvant therapy using receiver operating characteristic curve (ROC) and multivariate logistic regression analysis. After preoperative neoadjuvant therapy of rectal MC, the rate of pathological complete response, tumour downstaging, tumour response, and lymph node downstaging were 9%, 48%, 39% and 58%, respectively. Tumour downstaging more frequently occurred in patients with a mucus pool volume ratio of at least 68.3% (area under the ROC curve [AUC], 0.793 with 95% confidence interval [CI]: 0.693-0.893), and at least 62.1% for identifying those with a higher tumour response with an AUC of 0.739 (95% CI: 0.630-0.847). A higher volume ratio of mucus pool in patients with MC may be related to more tumour downstaging and therapy response, and therefore, could serve as an independent imaging biomarker for predicting tumour response to neoadjuvant therapy.