Colorectal cancer staging (TNM system)

The primary staging system recommended for colorectal cancer (CRC) is the American Joint Committee on Cancer (AJCC) TNM system.

The  TNM system classifies cancer based on three key factors: the size and extent of the primary tumor (T), whether the cancer has spread to nearby lymph nodes (N), and the presence of distant metastasis (M).

Each factor is assigned a numerical value, with higher numbers indicating more advanced disease.

The T classification ranges from Tx (primary tumor cannot be assessed) to T4b (tumor directly invades or adheres to adjacent organs or structures).

The N classification ranges from Nx (regional lymph nodes cannot be assessed) to N2b (7 or more positive regional lymph nodes).

The TNM system is the globally recognized system used for staging different types of cancers, including colorectal cancer, and is a critical component of colorectal carcinoma pathology reporting.

Colorectal cancer staging-

Primary tumor (T)

Tis Carcinoma in situ

T1 Tumor invades the submucosa

T2 Tumor invades the muscularis propia

T3 Tumor invades the perirectal fat

T4 Tumor directly invades adjacent organs, structures and/or perforates the visceral peritoneum

Regional lymph nodes (N)

Nx Tumor cannot be assessed

N0 No regional metastases

N1 Metastases in 1-3 nodes

N2 Metastases in ≥ regional lymph node

Distant Metastases

Mx distant metastases cannot be assessed

M0 No distant metastases

M1 Distant metastases

Staging

Stage 0 TisN0M0

Stage 1 T1-2N0M0

Stage IIA T3N0M0

Stage IIB T4N0M0

Stage IIIA T1-2N1M)

Stage IIIB T3-4N1M0

Stage IIIC Any TN2M)

Stage IV Any T Any N M1

NCI-estimated 5 year relative survival rates for localized colon cancer, lymph node negative, regional disease, lymph node positive, and distant, metastatic disease are 89.9%, 71.3% and 13.9&, respectively.

The 5 year survival rate for stge I and early-stage II is estimated at 97% with surgery alone.

Survival rate drops to 60% for high-risk stage II tumors (T4aN0) and down to 50% or less for stage IIT4N0 or stage III cancers.