Revised TN categorization for colon cancer based on national survival outcomes data

Abstract

Purpose: The sixth edition of American Joint Committee on Cancer (AJCC) Cancer Staging Manual for colon cancer subdivided stage II into IIA (T3N0) and IIB (T4N0) and stage III into IIIA (T1-2N1M0), IIIB (T3-4N1M0), and IIIC (anyTN2M0). Subsequent analyses supported revised substaging of stage III because of improved survival for T1-2N2 versus T3-4N2 and T4N1 survival was more similar to T3-4N2 than to T3N1. The AJCC Hindgut Taskforce sought population-based validation that depth of invasion and nodal status interact to affect survival.

Patients and methods: Surveillance, Epidemiology, and End Results (SEER) population-based data from January 1992 to December 2004 for 109,953 colon cancer patients were compared with National Cancer Data Base (NCDB) data on 134,206 patients. T4N0 cancers were stratified by tumors that perforate visceral peritoneum (T4a) versus tumors that invade or are adherent to adjacent organs or structures (T4b). N1 and N2 were stratified by number of involved positive lymph nodes (N+): N1a/N1b (1 v 2-3), N2a/N2b (4 to 6 v > or = 7). Five-year observed and relative survival data were obtained for each TN category.

Results: SEER rectal cancer analyses confirm that T1-2N2 cancers have better prognosis than T3-4N2,T4bN1 have similar prognosis to T4N2, T1-2N1 have similar prognosis to T2N0/T3N0, and T1-2N2ahave similar prognosis to T2N0/T3N0 (T1N2a) or T4aN0 (T2N2a). Prognosis for T4a lesions is betterthan T4b by N category. The number of positive nodes affects prognosis.

Conclusion: This SEER population-based colon cancer analysis is highly consistent with rectal cancer pooled analysis and SEER rectal cancer analyses, supporting the shift of T1-2N2 lesions from IIIC to IIIA/IIIB, shifting T4bN1 from IIIB to IIIC, subdividing T4/N1/N2, and revising substaging of stages II/III. Survival outcomes by TN category for colon and rectal cancer are strikingly similar.

Fig 1.

Interaction among T and N classifications and total nodes examined on 5-year relative survival rate in colon cancer, Surveillance, Epidemiology, and End Results (SEER) analysis. (A-E) Relative survival for pT1-4 by N1a (one positive lymph node), N1b (two to three positive lymph nodes), N2a (four to six positive lymph nodes), and N2b (≥ seven positive lymph nodes) on 109,953 patients, SEER analysis. The effect of total number of nodes examined is categorized along the abscissa. Relative survival improves for most TN categories as the number of lymph nodes examined increases. Data reprinted with permission et al.

Fig 2.

Observed 5-year survival by TN category. In the current Surveillance, Epidemiology, and End Results (SEER) colon cancer analysis and the previously reported SEER rectal cancer analysis, 5-year survival is strikingly similar by TN category of disease for patients with rectal or colon cancers.