MRI differences between locally advanced rectal mucinous adenocarcinoma and non-mucinous adenocarcinoma before and after neoadjuvant chemoradiotherapy / 中华放射学杂志

ABSTRACT

Objective:To investigate the MRI differences between locally advanced rectal mucinous adenocarcinoma and non-mucinous adenocarcinoma before and after neoadjuvant chemoradiotherapy (NCR).Methods:A retrospective cohort study was conducted to collect the clinical and imaging data of 165 patients with locally advanced rectal adenocarcinoma treated by NCR combined with surgery from October 2016 to October 2019 in the Sixth Affiliated Hospital of Sun Yat-sen University, 36 cases were rectal mucinous adenocarcinoma and 129 cases were non-mucinous adenocarcinoma. The image features of the two groups before and after NCR were evaluated based on MRI, including the length and thickness of the tumor, the distance from the lower edge of the tumor to the anal edge, T stage, N stage, involvement of mesorectal fascia (MRF) and peritoneal reflux. The difference of NCR and the change of MRI characteristics after NCR were compared by independent sample t test, Mann-Whitney U test or χ 2 test. The accuracy of MRI re-staging after NCR was evaluated according by postoperative pathological staging results. Results:Before NCR, there was significant difference in length of tumor between mucinous adenocarcinoma and non-mucinous adenocarcinoma groups ( P=0.044), there was no significant difference in the distance from the lower edge of the tumor to the anal edge, thickness of the tumor, T stage, N stage, involvement of MRF and peritoneal reflux (all P>0.05). After NCR, in patients with non-mucinous adenocarcinoma, the distance reduction from the lower edge of the tumor to the anal edge, the length reduction of the tumor, the thickness reduction of the tumor, the T-stage decline rate were significantly higher than those in the mucinous adenocarcinoma group (all P<0.05). The N-stage decline rate of mucinous adenocarcinoma was higher than that in non-mucinous adenocarcinoma group ( P=0.008). After NCR, MRI overestimated T staging of patients with both mucinous adenocarcinoma and non-mucinous adenocarcinoma compared with pathological T-stage ( P<0.001). In patients with mucinous adenocarcinoma, MRI overstated the N-stage than pothology ( P=0.001). Conclusions:There is different sensitivity of mucinous adenocarcinoma and non-mucinous adenocarcinoma to NCR. Patients with non-mucinous adenocarcinoma benefit more from the efficacy of NCR. The accuracy of MRI in re-staging of rectal mucinous adenocarcinoma and non-mucinous adenocarcinoma after NCR needs to be improved.