Cancer staging is a way to classify and describe the extent of a person’s cancer. Knowing the stage of cancer is important because it helps doctors determine the best treatment options and predict a patient’s prognosis. Cancer staging provides a common language for cancer care and treatment. The stage of a cancer describes how far the cancer has spread. It can be determined by:
- The size and location of the original (primary) tumor
- Whether cancer has spread to nearby lymph nodes
- Whether cancer has metastasized and spread to other organs or parts of the body
The staging system most often used for most types of cancer is the TNM system from the American Joint Committee on Cancer (AJCC). In this system:
- T refers to the size and extent of the main tumor
- N refers to whether or not the cancer has spread to nearby lymph nodes
- M refers to whether the cancer has metastasized and spread to other organs or parts of the body
Using this TNM system, a number is added to each letter to indicate size, extent, and spread. Higher numbers indicate more advanced disease. Once a T, N, and M category has been determined, an overall cancer stage of 0, I, II, III, or IV is assigned, with stage 0 being in situ, stage I being early, and stage IV being the most advanced disease.
Diagnostic Tests Used in Staging
There are many diagnostic tests that may be used to help determine the stage of cancer. These include:
- Physical exam: A physical exam allows doctors to feel for any enlarged lymph nodes, lumps or tumors that may indicate cancer spread.
- Biopsy: A biopsy removes a sample of the suspected cancer for examination under a microscope. This helps confirm cancer and may provide information about the type of cancer cells.
- Imaging tests: Imaging tests like X-rays, CT scans, MRIs, PET scans, and ultrasounds allow doctors to see tumors in the body and determine their size and location. They can also help identify cancer spread.
- Lab tests: Blood tests, urine tests, and other lab tests allow doctors to examine samples for abnormal cells shed by tumors. Tumor markers, proteins found in higher than normal amounts if cancer is present, can also be detected.
- Endoscopy: Inserting a tube with a camera into the body (endoscopy) lets doctors directly see tumors in organs like the bladder, colon, or stomach.
- Pathology: Examining cells and tissue samples under a microscope can provide information about whether cancer has spread and the type of cells involved.
Not every test listed will be used for every cancer diagnosis and staging. The doctor will determine which tests to use based on the type of cancer suspected, signs and symptoms, and other factors.
Stages of Cancer
The stage of cancer is determined by combining all the information gained from diagnostic tests and exams about the TNM categories. Here is an overview of what the stages mean:
Stage 0: Also called carcinoma in situ or precancerous, stage 0 refers to abnormal cells that have not spread to nearby tissue. These early cancer cells can often be removed through surgery.
Stage I: This is an early stage cancer where the tumor is small and has not grown deeply into nearby tissues (T1) and has not spread to lymph nodes (N0) or other parts of the body (M0).
Stage II and III: These indicate larger primary tumors and/or cancer that has spread to nearby lymph nodes, but not yet other organs. Higher numbers indicate more extensive disease.
Stage IV: This stage means the cancer has spread from where it started to distant organs or tissue (M1). It may also have spread to lymph nodes (any N) and the primary tumor may be any size (any T).
Stage Grouping
The TNM categories are combined into overall stage groupings:
| Stage | TNM Combination |
|---|---|
| Stage 0 | Tis, N0, M0: Carcinoma in situ. Abnormal cells present but have not spread. |
| Stage I | T1, N0, M0: Small tumor limited to organ of origin. |
| Stage II | T2 or T3, N0, M0: Larger primary tumor but no spread to lymph nodes or other organs. |
| Stage III | T1 to T3, N1+: Tumor has spread to regional lymph nodes but not distant sites. |
| Stage IV | T1 to T4, N0+ or N1+, M1: Tumor has metastasized to distant organs or tissue. |
Specific Cancer Staging
While this TNM system forms the foundation, the detailed staging criteria for each type of cancer is much more complex. Some key points about staging for major cancer types include:
Breast Cancer Staging
Breast cancer staging depends on:
- Tumor size
- Lymph node involvement
- Tumor grade
- Hormone receptor status
The stages of breast cancer are:
- Stage 0: Non-invasive breast carcinoma in situ.
- Stage IA: Tumor 2 cm or less in size with no lymph node involvement.
- Stage IB: No tumor but cancer cells in lymph nodes OR tumor 2 cm or smaller with spread to 1-3 lymph nodes.
- Stage IIA: Tumor 2-5 cm with spread to 1-3 lymph nodes OR tumor larger than 5 cm with no lymph node spread.
- Stage IIB: Tumor larger than 5 cm with spread to 1-3 nodes OR tumor 2-5 cm with spread to 4-9 nodes.
- Stage IIIA: Tumor larger than 5 cm with spread to 4-9 nodes OR tumor larger than 2 cm with extensive nodal involvement.
- Stage IIIB: Tumor of any size with spread to the chest wall or skin.
- Stage IIIC: No tumor or tumor of any size with cancer spread to 10+ lymph nodes.
- Stage IV: Distant metastatic breast cancer.
Lung Cancer Staging
Lung cancer staging is based on:
- Primary tumor size and location
- Involvement of lymph nodes
- Metastasis
The stages of lung cancer are:
- Stage 0: Carcinoma in situ.
- Stage IA: Tumor 3 cm or less with no spread to lymph nodes.
- Stage IB: Tumor larger than 3 cm but smaller than 5 cm with no lymph node spread.
- Stage IIA: Tumor 5 cm or smaller with spread to nearby lymph nodes OR tumor larger than 5 cm without lymph node involvement.
- Stage IIB: Tumor larger than 5 cm with spread to lymph nodes OR tumor of any size with spread to main bronchus, chest wall, pleura, phrenic nerve, or mediastinum (area separating lungs).
- Stage IIIA: Cancer in lymph nodes further from the primary tumor OR spread to tissues near the lung.
- Stage IIIB: Tumor of any size with more extensive regional lymph node involvement.
- Stage IV: Metastatic lung cancer affecting distant organs or areas beyond the chest.
Colon and Rectal Cancer Staging
For colon and rectal cancers, staging is based on:
- How far the tumor penetrates the wall of the colon or rectum
- Lymph node involvement
- Metastasis
The stages are:
- Stage 0: Carcinoma in situ in the inner lining of the colon or rectum.
- Stage I: Tumor has grown into the layers of the colon or rectum but not lymph nodes or other organs.
- Stage IIA: Tumor has grown into the wall of the colon or rectum and spread to 1-3 nearby lymph nodes.
- Stage IIB: Tumor has grown into tissues near the colon or rectum but not lymph nodes.
- Stage IIC: Tumor has grown through the wall and surrounding tissues without lymph node involvement.
- Stage IIIA: Tumor has grown through wall of colon or rectum and spread to 4-6 nearby lymph nodes.
- Stage IIIB: Tumor has grown through wall and spread to 7 or more nearby lymph nodes.
- Stage IIIC: Tumor has spread to lymph nodes along major blood vessels leading to the colon or rectum.
- Stage IV: Distant spread to liver, lungs, peritoneum (abdominal lining) or ovaries.
Prostate Cancer Staging
Key factors in prostate cancer staging include:
- Primary tumor size and location
- Gleason score indicating cancer aggressiveness
- PSA levels in the blood
- Spread to lymph nodes or other organs
The stages of prostate cancer are:
- Stage I: Cancer is found incidentally in a small part of one lobe of the prostate.
- Stage IIA: Tumor involves up to half of one lobe of the prostate.
- Stage IIB: Tumor has grown into more than half of one lobe of the prostate.
- Stage III: Tumor has spread through the prostate capsule and into nearby tissues.
- Stage IV: Cancer has spread to lymph nodes, bones, or other organs.
Bladder Cancer Staging
Bladder cancer staging is based on:
- Depth of invasion into the bladder wall
- Spread to fatty tissue around the bladder
- Involvement of lymph nodes or other organs
The stages are:
- Stage 0a: Non-invasive papillary carcinoma.
- Stage 0is: Carcinoma in situ – abnormal cells in bladder lining.
- Stage I: Cancer has spread to connective tissue under lining of bladder.
- Stage II: Cancer has spread to muscles of bladder wall.
- Stage III: Tumor is growing into fatty tissue around bladder and may have spread to reproductive organs.
- Stage IV: Cancer has spread to lymph nodes, bones, lungs or liver.
Determining Your Cancer Stage
Diagnostic tests like biopsies, imaging scans, endoscopies, and blood tests provide information about the TNM factors that will allow your cancer care team to determine an overall stage for your cancer. Ask your doctor to explain your cancer stage in a way you understand. Knowing your stage will help you understand the recommended treatment plan and overall prognosis.
The cancer stage may need to be adjusted over time as more information is gained during treatment or if the cancer progresses. Doctors use restaging to update your cancer stage when new test results provide more details about the extent of the cancer in your body.
Importance of Accurate Staging
Correctly determining the stage of cancer is crucial for getting the best treatment. If cancer staging is inaccurate:
- Cancer could be undertreated, allowing disease progression.
- Unnecessary aggressive treatment could be given for early stage disease.
- Drugs targeted for advanced cancers may be used when not needed.
- Research trials may include participants at wrong stages.
- Prognosis predictions will be inaccurate.
Speak with your doctor if you have any concerns that your cancer may be incorrectly staged or you do not understand how your stage was determined. Getting the staging right is key for successfully fighting cancer.
What Cancer Stage Means for Treatment
The stage of cancer helps guide the treatment plan. In general:
- Stage 0 may only need surgery or close monitoring if it is likely to progress.
- Stages I and II can often be treated with surgery alone or surgery plus radiation or chemotherapy.
- Stage III usually involves a combination of surgery, radiation, and chemotherapy.
- Stage IV cancers have spread too much for surgery alone so systemic drug therapies like chemotherapy are used.
But every cancer differs, so your doctor will recommend a treatment strategy tailored to your type and stage of cancer. The cancer stage will also provide information on prognosis that can help you make informed decisions about treatment approaches.
Prognosis Based on Cancer Stage
While cancer stage correlates with outlook, prognosis is based on many factors beyond just the stage. But in general:
- Stage 0 or I cancers usually have excellent prognoses, with 5-year survival over 90% for many cancer types.
- Stage II and III cancers still have relatively favorable prognosis, with 5-year survival usually 50% or higher.
- Stage IV metastatic cancers have poorer outlooks depending on the cancer type, with some 5-year survival rates 15% or less.
However, these statistics provide only a very rough estimate of prognosis. Factors like your age, overall health, cancer cell type, and response to treatment all impact cancer survival. Your doctor can provide prognosis estimates specific to your cancer situation.
Conclusion
Cancer staging provides a valuable standardized method for classifying tumor size and spread in the body. The stage is determined using information gained from exams, biopsies, imaging tests, and other procedures. This allows the cancer care team to decide on appropriate treatment options and estimate prognosis. Make sure you understand how your cancer was staged and what your stage means for managing your cancer going forward.