Stage migration resulting from inadequate number of examined lymph nodes impacts prognosis in stage II colon cancer after radical surgery.

PURPOSE

We evaluated the impact of examined lymph node (ELN) number on the prognosis of stage II colon cancer after radical surgery and developed a novel prognostic scoring system by combining primary tumor extension (pT) and ELN number for reclassification of stage II colon cancer.

METHODS

Three cohorts of patients diagnosed with colon cancer between 2004 and 2010 were identified from the Surveillance, Epidemiology, and End Results (SEER) database. Univariate and multivariate analyses were performed to evaluate the relationship between factors and patients' survival including cause-specific survival (CSS) and overall survival (OS). Survival curves from subgroups were plotted by the Kaplan-Meier method and compared by the log-rank test.

RESULTS

Cohort 1 and cohort 2 consisted of 13,960 and 5312 stage II colon cancer patients, respectively. Cohort 3 consisted of 4713 stage III patients. Factors including ELN, age, and pT were found to be associated with patients' survival in cohorts 1 and 2. Patients who were older or with smaller tumors were more likely to experience inadequate ELN. Patients with a higher score, as calculated by the novel scoring system, showed worse survival. Compared with stage III colon cancer patients, stage II patients with high scores had a comparable or even worse survival than stage IIIA and IIIB patients.

CONCLUSION

Inadequate ELN leads to understaging in stage II colon cancer and predicts inferior prognosis. Our analyses show that the novel prognostic scoring system, consisting of combined pT and ELN, quantified stage migration effect and can be applied to the reclassification of stage II colon cancer.