The prognostic factors of primary colorectal sarcoma and the clinical outcomes of negative lymph node dissection

Background: Primary colorectal sarcoma is an extremely rare malignancy that is associated with poor patient outcomes. The aim of this study was to identify the prognostic factors of primary colorectal sarcoma and evaluate the clinical outcomes associated with these prognostic factors. Methods: Between January 1, 2000 and December 31, 2016, the clinical data of 315 patients with primary colorectal sarcoma were obtained from the Surveillance, Epidemiology, and End Results (SEER) database. Cancer-specific survival (CSS) was analyzed by the Kaplan-Meier method and by log-rank test. The prognostic factors were identified by univariate and multivariate Cox regression analysis and hazard ratio (HR) and 95% confidence interval (CI) of covariates were also estimated. The optimal cutoff value for NLN count at dissection was identified using X-tile software and validated by univariate Cox regression analysis. Results: Of the 315 patients with primary colorectal sarcoma identified, 88.6% received surgery. The median follow-up time was 34 months with an interquartile range (IQR) of 9-79 months. The 5-year rate of CSS was 76.73% and 27.8% for the surgery group and the non-surgery group, respectively (P<0.0001). Univariate and multivariate Cox regression analysis performed on the data of nonmetastatic patients demonstrated that sex, race, radiotherapy, and chemotherapy had no effect on patient CSS, with age, tumor site, tumor grade, and NLN dissection being independent prognostic factors. A significant correlation was found between advanced age (>80 years old) and poor CSS (HR 1.964; 95% CI: 1.005-3.839; P=0.048). There were also significant correlations between colonic tumors and poor CSS (HR 2.903; 95% CI: 1.348-6.250; P=0.006) and grade IV tumors and poor CSS (HR 3.431; 95% CI: 1.725-6.823; P<0.001), while NLN dissection was associated with improved CSS (HR 0.946; 95% CI: 0.911-0.983; P=0.004). X-tile software analysis was used to determine that the optimal cutoff value for NLN count was 13. Patients who received NLN dissection with a cutoff value of 13 or more displayed better CSS than those who did not (P=0.016). Conclusions: Primary colorectal sarcoma patients can benefit significantly from primary tumor surgery. Age, tumor site, grade and NLN dissection are independent prognostic factors for CSS in nonmetastatic patients. Importantly, nonmetastatic patients treated with NLN dissection with an NLN count of 13 or more have significantly better CSS.