Cancer staging

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Cancer staging is the process of determining the extent to which a

Cancer staging can be divided into a clinical stage and a pathologic stage. In the

• Clinical stage is based on all of the available information obtained before a surgery to remove the tumor. This stage may include information about the tumor obtained by physical examination, blood tests, radiologic examination, biopsy, and endoscopy.
• Pathologic stage adds additional information gained by examination of the tumor
  pathologist
  after it has been surgically removed.

Because they use different criteria, clinical stage and pathologic stage often differ. Pathologic staging is usually considered to be more accurate because it allows direct examination of the tumor in its entirety, contrasted with clinical staging which is limited by the fact that the information is obtained by making indirect observations of a tumor which is still in the body. However, clinical staging and pathologic staging often complement each other. Not every tumor is treated surgically, so pathologic staging is not always available. Also, sometimes surgery is preceded by other treatments such as chemotherapy and radiation therapy which shrink the tumor, so the pathologic stage may underestimate the true stage.

Considerations

Correct staging is critical because treatment (particularly the need for pre-operative therapy and/or for adjuvant treatment, the extent of surgery) is generally based on this parameter. Thus, incorrect staging would lead to improper treatment.

For some common cancers the staging process is well-defined. For example, in the cases of breast cancer and prostate cancer, doctors routinely can identify that the cancer is early and that it has low risk of metastasis.

Pathologic staging, where a pathologist examines sections of tissue, can be particularly problematic for two specific reasons: visual discretion and random sampling of tissue. "Visual discretion" means being able to identify single cancerous cells intermixed with healthy cells on a slide. Oversight of one cell can mean misstaging and lead to serious, unexpected spread of cancer. "Random sampling" refers to the fact that lymph nodes are cherry-picked from patients and random samples are examined. If cancerous cells present in the lymph node happen not to be present in the slices of tissue viewed, incorrect staging and improper treatment can result.

Current research

New, highly sensitive methods of staging are in development. For example, the

Systems

Staging systems are specific for each type of cancer (e.g.,

• Lymphoma: most use Ann Arbor staging
• Hodgkin lymphoma: follows a scale from I to IV and can be indicated further by an A or B, depending on whether a patient is non-symptomatic or has symptoms such as fevers. It is known as the "Cotswold System" or "Modified Ann Arbor Staging System".^[2]

Solid

For solid tumors, TNM is by far the most commonly used system, but it has been adapted for some conditions.

• Brain cancer: For most brain cancers, no staging systems are available and they are instead graded. Embryonal CNS tumors like medulloblastoma are staged following a classification developed by Chang et al.^[3][4]
• Breast cancer: In breast cancer classification, staging is usually based on TNM,^[5] but staging in I–IV may be used as well.
• FIGO" system has been adopted into the TNM system. For premalignant dysplastic changes, the CIN (cervical intraepithelial neoplasia) grading system is used.^[6]
• Dukes staging system). More recently, colon cancer staging is indicated either by the original A-D stages or by TNM.^[7]
• Kidney cancer: uses TNM.^[8]
• Cancer of the larynx: Uses TNM.^[9]
• Liver cancer: Uses TNM.^[10]
• Lung cancer: uses TNM.^[11]
• Melanoma: TNM used. Also of importance are the "Clark level" and "Breslow depth" which refer to the microscopic depth of tumor invasion ("Microstaging").^[12]
• Prostate cancer: TNM almost universally used.^[13]
• blood serum
  markers (TNMS).
• Non-melanoma skin cancer: uses TNM.
• Bladder cancer: uses TNM.^[14]

Overall stage grouping

Overall Stage Grouping is also referred to as Roman Numeral Staging. This system uses numerals I, II, III, and IV (plus the 0) to describe the progression of cancer.

• Stage 0: carcinoma in situ, abnormal cells growing in their normal place ("in situ" from Latin for "in its place").
• Stage I: cancers are localized to one part of the body. Stage I cancer can be surgically removed if small enough.
• Stage II: cancers are locally advanced. Stage II cancer can be treated by chemotherapy, radiation, or surgery.
• Stage III: cancers are also locally advanced. Whether a cancer is designated as Stage II or Stage III can depend on the specific type of cancer; for example, in
  Hodgkin's Disease
  , Stage II indicates affected lymph nodes on only one side of the diaphragm, whereas Stage III indicates affected lymph nodes above and below the diaphragm. The specific criteria for Stages II and III therefore differ according to diagnosis. Stage III can be treated by chemotherapy, radiation, or surgery.
• Stage IV: cancers have often
  metastasized, or spread to other organs or throughout the body. Stage IV cancer can be treated by chemotherapy, radiation, or surgery. Despite treatment, a patient's mortality rate can be significantly higher with Stage IV cancer, e.g., the cancer can progress to become terminal
  .