Objective: To assess the rationality of the seventh edition of TNM staging system on tumor deposits (TDs) and propose a novel subclassification.
Summary background data: The TDs had been debated for many years. The seventh edition of TNM staging system proposed a "pN1c" concept. However, the value of the modification is still debated.
Methods: A total of 1541 patients with colorectal cancer were reviewed. Overall survival rates were compared between patients without LNM but TD (+), and those who were TD (-). The TDs were stratified into the "any T + any N" category. Two-step multivariate analysis was performed to identify significant prognostic factors. Univariate analysis was used to determine whether a correlation existed between the number of TDs and prognosis.
Results: There was a significant prognostic difference between patients without LNM or TDs compared with those with positive TDs. Only in T3N2bM0 there was a significant prognostic difference between LNM (+), TD (+) patients and TD (-) patients. The seventh edition of TNM staging system was substituted by the novel TNM staging system in 2-step multivariate analysis. Only in T3N1cM0 there was a significant prognostic difference between patients with only 1 TD and those with more than 1 TD.
Conclusion: The seventh edition of TNM staging system on TDs satisfactorily predicts patients' outcome for those without LNM. Patients who categorized as T3N2bM0TD (+) and T4N2bM0TD (-/+) should be reclassified as stage IV. Number of TDs was not an independent prognostic parameter in the TNM staging system.