A closer look at the number of lymph nodes examined in colorectal cancer: A VAMC experience

Abstract

e15117 Background: Retrieval of 12 lymph nodes (LN) is a current benchmark in colorectal cancer (CRC) resections according to the National Quality Forum (NQF). Series of multiple institutions contain variability in surgical and pathologic techniques for lymph node retrieval. To ensure consistency in retrieving lymph nodes for satisfactory staging, we present a 12 year experience by a single surgeon and single pathology lab at one VAMC on 157 patients (mean age 67) undergoing CRC resection. Furthermore, the use of chemotherapy for Stage II patients <12 LN retrieved is controversial and yields only a small survival benefit. Methods: The records of 157 patients from one surgeon's case log from 1994–2007 were reviewed. Strict guidelines were applied to remove the same distribution of pericolonic fat. The lab followed a two step approach to LN dissection: Step 1 search for grossly identifiable LN; Step 2 overnight Carnoy's immersion to find smaller LN. Statview and SAS software analyzed 1)Overall survival (OS) and association with finding >12LN; 2)Number of LN identified and impact on AJCC tumor stage (TS) and overall survival; 3)Number of LN and WHO tumor grade (TG) with OS; 4)The impact of number of positive LN on OS. Results: Our mean LN found (14.75) is higher than the 12 recommended by the NQF and is not significantly associated with OS regardless of AJCC TS(p=0.06). The mean LN per TS was I=13.4(N=41)/II=16.3(N=56)/ III=14.3(N=38)/IV 14.2(N=22). Number of LN identified was not statistically significant in predicting TS(p=0.42) or OS(p=0.24). WHO TG is significantly associated to decreased OS, but only in AJCC TS II/III/IV and not stage I (Ip>0.05/IIp=0.008/ IIIp=0.01/IVp=0.025). Higher number of positive LN was associated with lower OS (per each +LN, survival decreases by 0.15 months p=0.001) Conclusions: Contrary to multicenter studies, total number of LN identified does not impact AJCC TS or OS. Higher WHO TG and higher number of positive LN is associated with worse OS. This suggests that the tumor biology is more indicative of OS rather than host response (reactive lymphoid tissue) to the tumor. Stage II patients <12 LN may not be ‘high risk’ and adjuvant chemotherapy based on this factor alone should be reconsidered. Further studies would be warranted. No significant financial relationships to disclose.