The tumor (T), node (N), metastasis (M) system is based on depth of tumor invasion into the colonic wall, the number of regional lymph nodes involved, and distant metastasis.
Traditionally, colon cancer has been designated as stage III based on nodal involvement regardless of the depth (T1-4) of tumor penetration.
In this study, a research team from the United States assessed a large cohort of patients with stage III colon cancer in order to determine whether subgroup stratification better defined outcome.
They analyzed over 50,000 patients with stage III colon cancer reported to the National Cancer Data Base, from 1987 to 1993.
Patients' observed survival was calculated by actuarial life table methods for 3 new node-positive subgroups (group IIIA = T1/2, N1, group IIIB = T3/4, N1, and group IIIC = any T, N2).
The team also tested the prognostic strength of selected covariates using a Cox proportional hazards model.
|5-year observed survival rates|
- IIIA = 60%
- IIIB = 42%
- IIIC = 27%
|Annals of Surgery|
The researchers found 3 distinct subcategories within a traditional stage III cohort of colonic cancer were identified.
The 5-year observed survival rates were significantly different for the 3 subcategories; IIIA 60%, IIIB 42%, and IIIC 27%.
Additionally, the team identified similar differences after stratification for treatment.
They discovered subgroup, modality of the first course of therapy, patient age, and tumor grade to be significant independent prognostic covariates, using a multivariate proportional hazards model.
Dr Frederick Greene's team concluded, "The current stage III designation of colon cancer excludes prognostic subgroups stratified for mural penetration (T1-4) or nodal involvement (N1 vs. N2).
"Analysis of a large data set supports stratification into three subsets, confirming the benefit of adjuvant chemotherapy in each subgroup.
"This strategy should be used in the reporting and staging of node-positive colon cancers."