To study the relationship between degree of mesorectal invasion and circumferential margin (CRM) status in rectal cancer by preoperative CT scan.

From February 2010 to February 2014, one hundred and twenty cases of rectal cancer were selected from Enshi Central Hospital, preoperative spiral CT examinations were performed on patients undergoing surgery. The mesorectal invasion and the status of CRM were followed up, and the relationship with prognosis was analyzed by Kaplan-Meier and Pearson method.

In the 120 patients, there were 51, 32 and 37 cases with mesorectal invasive degree of Ⅰ, Ⅱ, Ⅲ. In each degree group, there was 3.9%, 6.2% and 45.9% with local recurrence; distant metastasis incidence rate 13.7%, 28.1%, 59.5%; the 3-year survival rate was 86.3%, 65.6% and 32.4%, respectively. CRM status was positive in 21 cases, negative in 99 cases. Compared to the negative cases, local recurrence rate, the incidence of distant metastasis and mortality were higher in the positive cases (38.1% vs 13.1%, χ²=6.358, P=0.016; 66.7% vs 24.2%, χ²=11.236, P=0.001; 76.2% vs 27.3%, χ²=16.359, P=0.000). Survival analysis showed that the lower the invasive degree of the mesorectum, the higher the 3-year survival rate of the patients, and the mortality in patients whose CRM was negative was significantly lower than that in the positive patients (P=0.012). There was a negative correlation between the invasiveness of the mesorectum and the postoperative survival time (r=-0.52). The mortality of patients with negative CRM was significantly lower than that of the positive patients (P=0.005). A negative correlation between CRM status and postoperative survival time (r=-0.71) was found. Cox regression showed distant metastasis, the degree of mesorectal invasion, and CRM status were independent prognostic factors of survival.

Mesorectal invasion and circumferential resection margin status was negatively correlated with the survival time, while mesorectal invasion, circumferential resection margin status, and metastasis are important prognostic factors in patients with rectal cancer. Preoperative CT examination is worthy of attention.