Stage cT3 low rectal cancer: analysis of prognostic factors

Whether all cT3 low rectal cancer patients should receive neoadjuvant chemoradiotherapy (nCRT) remains controversial. The depth of invasion beyond the muscularis propria of the cT3 rectal cancer is of great significance to the selection of a treatment plan and the evaluation of prognosis.

A retrospective analysis was conducted of 187 patients with stage cT3 low rectal cancer, who had been treated at the Department of Colorectal Surgery, The First Affiliated Hospital of Xiamen University from June 2010 to December 2012. The patients were divided into the nCRT group (88 cases) and no-nCRT group (99 cases). Possible significant prognostic factors [i.e., primary tumor volume (PTV), cell differentiation, circumferential resection margin (CRM), nCRT, age, sex, carcinoembryonic antigen (CEA), lymph node status, surgical procedure, etc.] were collected for estimation of disease-free survival (DFS), distant metastases rate (DM), local recurrence rate (LR). Independent predictive factors or survival were determined using Cox proportional hazards model.

The mean PTV was 16.2±11.1 (2.07-72.68) cm³. In the univariate and multivariate analyses: nCRT hazards ratio (HR) =4.258, 95% confidence interval (CI): 1.912-9.483 (P<0.001); PTV HR =0.381, 95% CI: 0.181-0.804 (P=0.011); CRM HR =0.227, 95% CI: 0.097-0.532 (P=0.001). For the PTV ≤15 cm³ group, there were no significant differences between the nCRT and no-nCRT group in 3-year follow-up (P>0.05). For the PTV >15 cm³ group, there were significant differences between the nCRT and no-nCRT group in 3-year DFS (84.2% vs. 51.1%; P=0.001), DM (13.1% vs. 31.2%; P=0.017) and LR (2.9% vs. 26.6%; P=0.009). For the CRM negative group, there were significant differences between the nCRT and no-nCRT group in 3-year DFS (94.0% vs. 79.0%; P=0.008), LR (1.5% vs. 10.7%; P=0.028) and DM (4.5% vs. 13.5%; P=0.039).

For stage cT3 low rectal cancer patients, nCRT, PTV, and CRM were independent prognostic factors. NCRT may improve the survival of PTV >15 cm³ patients, but may not have a significant effect on patient with PTV ≤15 cm³ and CRM negative. Direct surgery is recommended for this group of patients.