Number of lymph nodes recovered as an independent prognostic factor in predicting outcome in patients with pathologically node-negative rectal cancer following preoperative chemo/radiotherapy.

Abstract

606 Background: To determine the importance of number of lymph nodes recovered on outcome in pathological node negative rectal cancer patients who had received chemo/radiotherapy prior to surgery. Methods: We retrospectively analysed data from 262 patients with locally advanced rectal cancer who received pre-operative chemo/radiotherapy at Castle Hill Hospital, Cottingham and Nottingham University Hospital between 2001 and 2008. Patients were treated with CT planned radiotherapy to a dose of 45-50 Gy in 25 fractions with concurrent fluoropyrimidine chemotherapy. Surgery was normally performed at an interval of 6-8 weeks. There were 152 patients who were found to be pathologically node negative for further analysis. Median follow-up was 51.5 months Patients were grouped into < 10 nodes recovered or > 10 nodes recovered. Disease free survival (DFS) and overall survival (OS) was assessed using Log rank test. Multivariate analysis was performed using Cox-regression analysis. Results: Of the 152 patients analysed, 67.1 % (n=102 ) had fewer than 10 nodes recovered and 32.8% (n=50) had greater than 10 nodes recovered. The median number of nodes recovered was 7 (range 0-39). There was a improvement in 5 year DFS and OS in group who had more than 10 nodes recovered compared to group with less than 10 nodes recovered ( DFS at 5yrs :86.5% vs. 61.5%, p=0.01, OS at 5 yrs : 77.8% vs. 67.4% , P =0.059). On multivariate analysis pathological T-stage , circumferential resection margin (CRM) status and number of lymph nodes recovered were found to be independent predictors of disease free survival (p=0.002). Conclusions: The number of lymph nodes retrieved following surgery for locally advanced rectal cancer patients following chemo/radiotherapy is an independent prognostic factor in pathologically node negative patients. This may need to be considered when making subsequent adjuvant chemotherapy decisions.