Effects of magnetic resonance imaging (MRI)-detected extramural vascular invasion (mrEMVI) and tumor deposits (TDs) on distant metastasis and long-term survival after surgery for stage III rectal cancer: a retrospective study grouped based on the relationship between the bottom of the tumor and peritoneal reflection

Background: To evaluate the effect of magnetic resonance imaging (MRI)-detected extramural vascular invasion (mrEMVI) and tumor deposits (TDs) on distant metastasis and long-term survival after surgery for stage III rectal cancer based on the relationship between the bottom of the tumor and peritoneal reflection.Methods: A retrospective study was performed on 694 patients who underwent radical resection for rectal cancer at the Harbin Medical University Tumor Hospital from October 2016 to October 2021. According to the surgical records, a new group was established based on the relationship between the lower end of the tumor and peritoneal reflection. On the peritoneal reflection group: the tumors are all located on the peritoneal reflection. Across the peritoneal reflection group: the tumors recurred across the peritoneal reflection. Under the peritoneal reflection group: the tumors are all located under the peritoneal reflection. We evaluated the effects of mrEMVI and TDs on postoperative distant metastasis and long-term survival of stage III rectal cancer by combining mrEMVI with TDs.Results: In the whole study population, neoadjuvant therapy (P=0.003) was negatively correlated with distant metastasis after rectal cancer surgery. Also, mesorectal fascia (MRF) (P=0.024), postoperative distant metastasis (P<0.001), and TDs (P<0.001) were independent risk factors for long-term survival after rectal cancer surgery. Lymph node metastasis (P<0.001) and neoadjuvant therapy (P=0.023) were independent risk factors for the presence or absence of TDs of rectal cancer. In the non-neoassisted subgroup, postoperative distant metastasis (P<0.001) was considered to be an independent risk factor for long-term survival after rectal cancer surgery.Conclusions: In the under the peritoneal reflection group, the combination of mrEMVI and TDs seems to play a certain guiding role in predicting distant metastasis and long-term survival after rectal cancer surgery.