No change in lymph node positivity rate despite increased lymph node yield and improved survival in colon cancer

Aim: To analyse trends over time in the number of lymph nodes evaluated and in the proportion of node positivity and to investigate the impact on survival for patients with colon cancer. Patients and methods: 8616 patients resected for M0 colon cancer diagnosed in the Southern Netherlands between 2000 and 2011 were included in this study. Trends in nodal evaluation and node positivity were analysed. Multivariable logistic regressions were used to assess the influence of period of diagnosis on adequate nodal evaluation (>= 12 lymph nodes) and node positivity after adjusting for patient and tumour characteristics. Crude 5-year relative survival was used as an estimate for disease-specific survival. Results: Overall, the proportion adequate nodal evaluation increased from 13% in 2000-2002 to 59% in 2009-2011 (p < 0.0001), whereas the proportion node positivity remained similar across study periods (approximately 35%). Patients diagnosed in later periods were more likely to have received adequate nodal yield (adjusted Odds ratio (OR) 2009-2011 versus 2000-2002 9.8, 95% Confidence interval (CI) 8.3-11.6). However, the adjusted odds of having node positive disease did not differ between periods of diagnosis. Relative excess risk of dying was independently correlated with the number of lymph nodes evaluated (1-8 LNs versus >= 12 LNs, N0: 2.2, 95% CI 1.7-2.9; N+: 1.7, 95% CI 1.4-2.0) and period of diagnosis (2009-2011 versus 2000-2002, N+ only: 0.8, 95% CI 0.6-1.0). Conclusion: The reason for improved survival with increased nodal yield is different from simple understaging as the proportion of lymph node positivity remained constant. (C) 2014 Elsevier Ltd. All rights reserved.