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Colorectal Cancer Staging

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Many different staging systems for colorectal cancer have been employed, but a single system is required to ensure a common language for clinicians. From the tumor, nodes, and metastasis system, it requires continuous evaluation and change. Staging may change based on updated testing and symptomatology. Magnetic resonance imaging (MRI) is presently the modality of choice for the local staging of rec;tal cancer, with positron emission tomography (PET) being optional for the evaluation of colorectal cancer.

The staging system that is used for all types of cancer groups is divided into five main categories. This staging system is more often used by cancer registries than by healthcare professionals, but is often described in the following ways:

  • In situ—meaning abnormal cells are present but have not spread to nearby tissue.
  • Localized—meaning the cancer is limited to the specific area.
  • Regional—meaning the cancer has spread to nearby lymph nodes, tissues, or organs.
  • Distant—meaning the cancer has spread to distant parts of the body.
  • Unknown—meaning that diagnostics cannot determine the staging.

The American Joint Committee on Cancer (AJCC) and a National Cancer Institute sponsored panel recommended that at least 12 lymph nodes be examined in patients with colon and rectal cancer to confirm the absence of nodal involvement. Outcome may be related to nodal involvement.

The AJCC uses the TNM classification to determine staging. The TNM classifies colorectal cancer in the following ways:

Stage 0:

  • Tis – Carcinoma in situ: intraepithelial or invasion of lamina propria.

Stage I:

  • T1 = Tumor invades submucosa.
  • T2 = Tumor invades muscularis propria.

Stage II:

  • T3 = Tumor invades through the muscularis propria into pericolorectal tissues.
  • T4a = Tumor penetrates to the surface of the visceral peritoneum.
  • T4b = Tumor directly invades or is adherent to other organs or structures.

Stage III:

Stage III is defined by the presence of metastasis. For this reason, Stage III tumors may include any previous T classification (T1, T2 etc.) but includes additional notation.

  • N1 = Metastases in 1–3 regional lymph nodes.
  • N1c = Tumor deposit(s) in the subserosa, mesentery, or nonperitonealized pericolic or perirectal tissues without regional nodal metastasis.
  • N2a = Metastases in 4–6 regional lymph nodes.
  • N2b = Metastases in ≥7 regional lymph nodes.
  • N2 = Metastases in ≥4 regional lymph nodes.

Stage IV:

Stage IV colorectal cancer can use any previous classification, in addition to:

  • M1b = Metastases in >1 organ/site or the peritoneum.

 

All classes may also use additional classification:

  • N0 = No regional lymph node metastasis.
  • M0 = No distant metastasis.
  • TX = Primary tumor cannot be assessed.
  • NX = Regional lymph nodes cannot be assessed.

 

Sources:

Cancer Staging. Retrieved from https://www.cancer.gov/about-cancer/diagnosis-staging/staging.

Colon Cancer Treatment. Retrieved from https://www.cancer.gov/types/colorectal/hp/colon-treatment-pdq/#section/…

Compton, CC and Greene, FL. (2004). The staging of colorectal cancer: 2004 and beyond. CA Cancer J Clin., 54(6), 295-308. Retrieved from https://www.clinicalkey.com/#!/content/medline/2-s2.0-15537574.

Lee, DH and Lee JM. (2017). Whole-body PET/MRI for colorectal cancer staging: Is it the way forward? J Magn Reson Imaging., 45(1), 21-35. Retrieved from https://www.clinicalkey.com/#!/content/medline/2-s2.0-27346172.