Impact of the number of nodes examined on survival in node negative small bowel adenocarcinoma: A SEER database analysis

Background: Adjuvant chemotherapy (AC) may have benefit in both node negative (N-) and node positive (N+) non-metastatic small bowel adenocarcinoma (SBA). In N- cases, increased number of nodes examined (NNE) has been associated with increased survival. The objective of this analysis was to determine whether N- status is associated with lower NE at time of curative surgery compared to N+ cases, and how many NNE represents adequate sampling. Methods: SAS 9.4 software and cases of non-metastatic SBA with complete AJCC staging (2004+) from the SEER database were used for this analysis. Age, gender, race, grade, NNE and T stage were compared between N+ and N- cases. Survival analysis using N- cases was performed to determine which nodal cut-offs and variables best predicted survival. Results: 613 cases of non-metastatic SBA (183 N- and 430 N+) diagnosed from 2004 to 2014 were analyzed. T stage and nodal sampling were the only two variables that differed statistically between N- and N+ cases (Table). Using the Log-rank test, a statistical separation in survival curves was identified at a minimum of > =13 NNE (p = 0.0136), a maximum of > =21 NNE (p = 0.0142), and with the greatest statistical separation at > =17 NNE (p = 0.0003). Out of age, gender, race, grade, > =13 NNE, > =17 NNE, > = 21 NNE, and T stage, only age, node cut-off of > =17 (HR 0.47, p=.0032) and T stage remained after stepwise selection of variables for Cox regression modelling. ROC's for Cox Regression models at 60 months, which included Age, T stage and either > = 13 NNE, > = 17 NNE, or > = 21 NNE were associated with AUC's of 0.700, 0.717 and 0.667, respectively.Table: 773PNode -Node +pMedian Nodes Sampled9120.0008Proportion of Cases by T StageT110.9%0.7%<.0001T211.5%1.6%<.0001T360.7%45.4%0.0006T416.9%52.3%<.0001 Open table in a new tab Conclusions: N- SBAs are associated with decreased nodal sampling compared to N+ SBAs. Low sampling is associated with decreased survival, possibly related to the presence of occult nodal disease. While further work is needed to determine what is considered adequate nodal sampling in N- SBA's, this analysis suggests that N- cases where less than 17 nodes have been examined have a poorer outcome. Legal entity responsible for the study: Maclean Thiessen. Funding: Has not received any funding. Disclosure: All authors have declared no conflicts of interest.