Abstract 846: Clinical relevance of lymph node evaluation in Stage II and III colon cancers
Authors: Shanmugam Chandrakumar , Hines Robert B. , Jhala Nirag C. , Bumpers Harvey L. , Posey James A. , Birdsong George , Manne Upender 
Published: February 2011

Abstract
Background: Although evaluation of at least 12 lymph nodes is recommended for accurate staging of colon cancer patients, there is still inconsistency in what constitutes adequate lymph node harvest.
Methods: We studied 521 colon cancer patients to assess the impact of the current guidelines of collecting at least 12 lymph nodes on cancer-specific survival and recurrence within 2 years after surgery, after adjustment for chemotherapy status, age, race, and tumor size and grade. In addition, patients were placed into categories of 1-6, 7-11, 12-19 and ≥ 20 lymph nodes harvested to evaluate the minimum number required for adequate staging of Stage II and III colon cancer patients. Also, in Stage III patients, the probability of finding lymph node metastases with respect to these quartiles was analyzed.
Results: Extraction of 12 lymph nodes as the cut-off point was not significantly associated with colon cancer mortality either in Stage II (HR = 0.66; 95% CI, 0.43-1.02) or Stage III (HR = 0.77; 95% CI, 0.53-1.11) patients. In Stage II and III patients, compared with category 1-6 lymph nodes harvested, collection of ≥20 lymph nodes had a 57% (Stage II, HR = 0.43; 95% CI, 0.23-0.83) and a 43% (Stage III, HR = 0.57; 95% CI, 0.32-1.00) decreased risk of mortality. Although statistically not significant, increased harvest of lymph nodes, especially ≥20 lymph nodes, was associated with reduced risk of recurrence in Stage II (HR = 0.41; 95% CI, 0.16-1.06) but not in Stage III patients (HR = 1.19; 95% CI, 0.47-3.02). For Stage III patients, linear regression analysis demonstrated, for every 8 additional lymph nodes collected, a 13% increased probability of finding a positive lymph node (parameter estimate=0.12601, p&lt; 0.0001). Logistic regression was utilized to obtain the probability of obtaining ≥4 positive lymph nodes (pN2). Patients with 1-6 lymph nodes extracted had a 31% (predictive probability (PP) =0.309) chance of having a tumor with pN2 stage. Patients with 7-11 and 12-19 nodes extracted had similar probabilities, at 35% (PP=0.352) and 37% (PP=0.367), respectively. Patients with ≥ 20 lymph nodes extracted had a 45% chance (PP=0.454) of having a pN2 tumor. Conclusions: These findings suggest that extraction of a minimum of twelve lymph nodes has not provided a useful cut-off point in determining accurate pathologic staging. For Stage III patients, harvest of every eight additional lymph nodes resulted in identification of a single positive node and the probability of finding a pN2 patient also increased with increasing numbers of lymph nodes harvested. Thus, to minimize stage misclassification, and to improve patient survival, emphasis should be on collection of as many lymph nodes as possible. These studies were supported by NCI/NIH grants, R03-CA139629, U54-CA118948, and R01-CA098932-01.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 846.