Abstract
Background and Aim: This work aims to study the relationship between MRI-defined mucin pool (MP) patterns prior to treatment and the efficacy of neoadjuvant therapy (NAT) in locally advanced rectal mucinous adenocarcinoma (RMAC).Methods: This retrospective study included 278 RMAC patients evaluated between January 2012 and January 2019. After having been trained by using 118 cases with postoperative pathological images, radiologists distinguished MRI-defined MP status as mixed type (MTMP) and separate type (STMP) in a NAT cohort (160 patients) in addition to tumor characteristics, invasion of mesorectal facia, and nodal status. Reader reproducibility was determined using the κ coefficient. The main outcome was the accuracy of MP dichotomy in predicting whether patients had tumor responsiveness or not.Results: Among 278 cases, MTMP and STMP accounted for 49.6 and 50.4% of MPs, respectively. A total of 72 patients received neoadjuvant chemoradiotherapy and 88 received chemotherapy. The tumor responsiveness rate in the chemoradiotherapy group was higher than that in the chemotherapy group (58.3 vs. 21.6%, P < 0.001). In the chemotherapy group, the tumor responsiveness rate in patients with MTMPs was lower than that in patients with STMPs (4.9 vs. 25.5%, P = 0.002). The baseline MRI-defined MTMP was associated with lower responsiveness rates after NAT in the chemotherapy group (odds ratio, 11.050, with 95% CI, 2.368–51.571, P = 0.002).Conclusions: MP dichotomy can be reliably evaluated by using MRI. In the chemotherapy group, MTMP may be a dependent predictor to indicate a lower likelihood of tumor responsiveness after NAT.
Highlights
Neoadjuvant therapy (NAT) followed by total mesorectal excision (TME) is the standard treatment for patients with locally advanced rectal cancer [1]
This study aimed to explore the prognostic effect of MRIdefined mucin pool (MP) type on tumor responsiveness after neoadjuvant therapy
As to the consistency between Magnetic resonance imaging (MRI)-defined and pathology-defined MP, the κ coefficient was 0.773 (Table S5)
Summary
Neoadjuvant therapy (NAT) followed by total mesorectal excision (TME) is the standard treatment for patients with locally advanced rectal cancer [1]. Rectal mucinous adenocarcinoma (RMAC) is a subtype of rectal cancer comprising about 6.2–12.3% of cases [2, 3]. Whether there is a need for individualized RMAC treatment options remains controversial [2, 6,7,8], and predicting the difference in curative effect in advance can provide a basis for the selection of neoadjuvant options. Magnetic resonance imaging (MRI), the recommended noninvasive tool in the guidelines, is often used to evaluate rectal cancer due to the high resolution of soft tissue. This work aims to study the relationship between MRI-defined mucin pool (MP) patterns prior to treatment and the efficacy of neoadjuvant therapy (NAT) in locally advanced rectal mucinous adenocarcinoma (RMAC)
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