Investigating the prognostic value of lateral mesorectum using preoperative high-resolution MRI in patients with rectal cancer.

Background: To explore the lateral mesorectum structures and develop a nomogram model for predicting the prognosis of rectal cancer (RC) patients using preoperative high-resolution magnetic resonance imaging (MRI).

Methods: Patients who underwent radical resection of RC in our hospital from January 2017 to December 2018 were retrospectively analyzed. Imaging data and postoperative 3-year prognosis data of patients were collected. The lateral mesorectum was observed, and related parameters were investigated: lateral interruption of the mesorectal fascia (LI-MRF), type of the middle rectal artery (MRA), and the maximum diameter of the MRA. The impact of lateral mesorectum parameters on prognosis was determined using Cox analysis and Kaplan-Meier (KM) survival curves. A nomogram combining lateral mesorectum parameters with clinical data was constructed and its predictive performance was validated.

Results: A total of 260 patients were included in this study. In preoperative high-resolution MRI, LI-MRF and MRA were observed bilaterally in all patients. Multivariate Cox regression analysis showed that the maximum diameter of the right MRA (P = 0.001) and right LI-MRF (P = 0.016) were predictive factors for postoperative 3-year overall survival (OS). Additionally, gender (P = 0.015), mrT stage (P = 0.025), and the maximum diameter of the right MRA (P = 0.002) were predictive factors for postoperative 3-year disease-free survival (DFS). The concordance indexes (C-index) of the predictive nomogram were 0.737 for OS and 0.685 for DFS.

Conclusion: Preoperative high-resolution MRI revealed that the lateral mesorectum and MRA were inherent. The right LI-MRF and the maximum diameter of the right MRA were risk factors for poor postoperative survival in RC patients.