Nodal status after preoperative chemoradiotherapy (CRT) in locally advanced rectal cancer: Prognostic evaluation of number of resected lymph nodes (LNs), metastatic resected LNs, and LN ratio in the National Cancer Institute of Brazil.

Abstract

e14568 Background: For accurate colon cancer staging, 12 or more LNs must be resected. However, in rectal cancer, preoperative CRT can decrease the number of evaluable LNs, and the cutoff for a minimum number of LNs retrieved is unclear, as well as the prognostic value of LN ratio. Methods: We evaluated all locally advanced rectal cancer that received CRT followed by standard surgery (TME) from 2002 to 2009. External radiotherapy consisted of 45 to 50.4 Gy in 5 weeks and concomitant chemotherapy was bolus 5-Fu/LV. Pre-treatment staging included abdominal and pelvic CTs, chest RXs, CEA, and physical examination. Clinical data was collected from medical records and surgical specimens were pathologically evaluated accordingly to Quirke's method. LN ratio was defined as the ratio of the number of positive LN and total number of LN examined. Kaplan-Meier overall survival (OS) and disease free survival (DFS) curves were obtained and compared using the Long-rank test. Categorical variables were assessed using Fish's exact test. Results: Of 202 patients included, 125 (62%) were low rectal cancers (5cm or less from anal verge). Surgery was performed in a mean time interval from CRT of 3.95 months (0.28-24), and the type of resection was a low anterior resection in 139 (64%) and abdominoperineal resection in 63 (36%). Only 42.5% received postoperative chemoterapy. LN metastasis at the vascular stump level were more frequent in cancers lying more than 5 cm above the anal verge (p=0.02). Median number of LNs found in the specimens was 12 (0-56). The number of resected LNs had no impact in prognosis within the cutoff levels of 7 or 12, neither when considering only ypN0 cases. A LN Ratio >0.15 was found in 33% of our patients, and associated to a decrease in OS (p<0.001) and DFS (p=0.01), and was the only variable associated to distant metastasis (p=0.048). Conclusions: Positive LNs after CRT severely impaired prognosis in patients treated with rectal cancer. A prognostic cutoff value for LN dissection were not achieved, but a LN ratio >0.15 seems to be a strong predictor of recurrence and cancer related death.