Determining the optimal number of examined lymph nodes for prognosis in colon cancer: a population-based study stratified by tumor location and T stage.

BACKGROUND

Clinical guidelines recommend ≥12 examined lymph nodes (ELNs) for colon cancer staging, but more may be necessary for accuracy. This study utilized nodal staging scores (NSS) to identity the optimal number of ELNs based on tumor location and T stage, and to assess its prognostic impact.

METHODS

Data from 80,792 patients in the Surveillance, Epidemiology, and End Results (SEER) database (2004-2014) and 2,300 patients from the West China Hospital (WCH) cohort (2008-2014) with stage I-III resected colon cancer were analyzed. Optimal ELNs was estimated using a β-binomial distribution model, stratified by tumor location (left-sided, LS; right-sided, RS) and T stage. The primary outcome was overall survival (OS). The association between sufficient nodal staging and OS in node-negative patients was validated by multivariate Cox models.

RESULTS

The mean number of ELN was 18.75 in the SEER and 14.58 in the WCH database. There were 57.8% and 48.8% patients who had RS colon cancer in the SEER and WCH database. Fewer T3-4 tumors were observed in the SEER cohort compared to the WCH cohort (68.4% 87.2%). Sufficient nodal staging required ≥24 ELNs for T3 tumors, ≥34 nodes for T4 LS tumors, and ≥40 nodes for T4 RS tumors. For T3 lesions, examining 20-29 ELNs were more likely to have node-positive disease [odd ratio (OR) 1.07; 95% confidence interval (CI): 1.01-1.12] compared to patients with 12-15 ELNs. In the T3N0 group, ELN ≥24 was independently associated with better OS in the SEER database [hazard ratio (HR) 0.72; 95% CI: 0.68-0.75], which was validated in the WCH cohort (HR 0.54; 95% CI: 0.38-0.76).

CONCLUSIONS

Optimal ELNs for adequate colon cancer staging is related to both T stage and tumor location. We recommend that ≥24 lymph nodes be examined for T3 tumors, ≥34 for LS T4 tumors and ≥40 for RS T4 tumors for sufficient staging.