Staging of Colorectal Cancer Staging
Staging is a method of evaluating the progression of the cancerthe tumor and the extent to which it has spread to other parts of the body. Once doctors determine the stage of colorectal cancer, they are better able to decide on the best course of treatment.
Colon cancer staging is relatively straightforward. Originally there was the Dukes classification system, which placed patients into one of three categories (Stages A, B, C). This system was subsequently modified by Astler-Coller to include a fourth stage (Stage D); Gunderson & Sosin subsequently modified the staging system again in 1978. More recently, the American Joint Committee on Cancer (AJCC) introduced the TNM staging system, which places patients into one of four stages (Stage I–IV).
Listed below are the Dukes and TNM staging systems (they are the most often used).
Modified Dukes Staging System for Colorectal Cancer
Modified Dukes A The tumor penetrates into the mucosa of the bowel wall but no further.
Modified Dukes B
- B1: tumor penetrates into, but not through the muscularis propria (the muscular layer) of the bowel wall
- B2: tumor penetrates into and through the muscularis propria of the bowel wall
Modified Dukes C
- C1: tumor penetrates into, but not through the muscularis propria of the bowel wall; there is pathologic evidence of colon cancer in the lymph nodes
- C2: tumor penetrates into and through the muscularis propria of the bowel wall; there is pathologic evidence of colon cancer in the lymph nodes
Modified Dukes D The tumor has spread beyond the confines of the lymph nodes to organs such as the liver, lung or bone
TNM (Tumor, Node, Metastasis) Staging System for Colorectal Cancer
- T1: Tumor invades submucosa
- T2: Tumor invades muscularis propria
- T3: Tumor invades through the muscularis propria into the subserosa, or into the pericolic or perirectal tissues.
- T4: Tumor directly invades other organs or structures, and/or perforates
- N0: No regional lymph node metastasis
- N1: Metastasis in 1 to 3 regional lymph nodes
- N2: Metastasis in 4 or more regional lymph nodes
- M0: No distant metastasis
- M1: Distant metastasis present.
Colorectal Cancer Stage Groupings
Stage I: T1 N0 M0; T2 N0 M0
Cancer has begun to spread, but is still in the inner lining.
Stage II: T3 N0 M0; T4 N0 M0
Cancer has spread to other organs near the colon or rectum. It has not reached lymph nodes.
Stage III: any T, N1-2, M0
Cancer has spread to lymph nodes, but has not been carried to distant parts of the body.
Stage IV: any T, any N, M1
Cancer has been carried through the lymph system to distant parts of the body. This is known as metastasis. The most likely organs to experience metastasis from colorectal cancer are the lungs and liver.