The American Joint Committee on Cancer (AJCC) has developed and compiled cancer staging references for quickly finding important information about different types of cancers. These references and tools are excellent resources for medical professionals treating patients with cancer.
What Is Cancer Staging?
Cancer staging is the process of determining how much cancer is in the body and where it is located. Staging describes the severity of an individual's cancer based on the magnitude of the original (primary) tumor as well as on the extent cancer has spread in the body. Understanding the stage of the cancer helps doctors to develop a prognosis and design a treatment plan for individual patients.
Staging provides a common language for doctors to effectively communicate about a patient's cancer and collaborate on the best courses of treatment.
Understanding the cancer's stage is also critical to identifying clinical trials that may be appropriate for particular patients.
What Are the Different Types of Staging?
Four different types of staging used:
- Clinical staging determines how much cancer there is based on physical examination, imaging tests, and biopsies of affected areas.
- Pathological staging can be determined when a patient has surgery to remove a tumor. Pathological staging combines the results of both the clinical staging with the surgical results.
- Post-therapy or post-neoadjuvant therapy staging determines how much cancer remains after a patient is treated with systemic therapy (chemotherapy or hormones) and/or radiation therapy prior to surgery or where no surgery is performed. This can be assessed by clinical staging guidelines after the therapy. It may also be assessed by pathological staging guidelines after surgery following the therapy.
- Recurrence or retreatment staging is used to determine the extent of the disease if a cancer comes back after treatment. Recurrence or retreatment staging helps determine the best treatment options for cancer that has returned.
What Are the Common Elements of Staging Systems?
Staging is based on commonly understood knowledge about the way cancer develops and spreads. In most cases, the stage is based on four main factors:
- Location of the primary (original) tumor
- Tumor size and extent of tumors
- Lymph node involvement (whether or not the cancer has spread to the nearby lymph nodes)
- Presence or absence of distant metastasis (whether or not the cancer has spread to distant areas of the body)
How Does Staging Work?
Doctors collect data about a cancer to determine its stage. This information comes from the various tests used to identify staging in different types of cancer.
These tests can include:
- Physical examinations, which may determine the location and size of the tumor(s) and provide additional information on whether the cancer has spread to the lymph nodes and/or to other organs
- Imaging tests such as x-rays, CT scans, and MRI scans, which can show the location of the cancer, size of the tumor, and whether the cancer has spread
- Laboratory tests, which provide information on blood, urine and other fluids, and tissues removed from the body
- Pathology reports, which can provide information about the size of the tumor, growth into other tissues and organs, type of cancer cells, and grade of tumor (how closely the cancer cells resemble normal tissue); pathology reports often confirm the diagnosis of cancer, as well as the stage.
- Surgical reports, which describe the size and appearance of a tumor and provide insights about lymph node and organ involvement
What Is the TNM Staging System?
The TNM Staging System was developed and is maintained by the AJCC and the Union for International Cancer Control (UICC). It is the most commonly used staging system by medical professionals around the world. The TNM classification system was developed as a tool for doctors to stage different types of cancer based on certain, standardized criteria.
The TNM Staging System includes the extent of the tumor (T), extent of spread to the lymph nodes (N), and presence of metastasis (M).
The T category describes the original (primary) tumor.
The N category describes whether or not the cancer has reached nearby lymph nodes
The M category tells whether there are distant metastases (spread of cancer to other parts of the body).
Because each cancer type has its own classification system, letters and numbers do not always mean the same thing for every kind of cancer. Once the T, N, and M are determined, they are combined and an overall stage of 0, I, II, III, IV is assigned. Sometimes these stages are subdivided as well, using letters such as IIIA and IIIB.
In some cancer types, non-anatomic factors are required for assigning the anatomic stage/prognostic group. These are clearly defined in each chapter of the AJCC Cancer Staging Manual (e.g., PSA and Grade Group in Prostate). These factors are collected separately from T, N, and M, which remain purely anatomic and are used to assign stage groups.
Where non-anatomic factors are used in groupings, there is a definition of the groupings provided for cases where the non-anatomic factor is not available (X) or where it is desired to assign a group ignoring the non-anatomic factor.
Stage I cancers are the least advanced and often have a better prognosis. Higher stage cancers are often more advanced but in many cases can still be treated successfully.
Does the Stage of a Cancer Change?
The formal stage of a cancer does not change over time, even if the cancer progresses. A cancer that returns or spreads is still referred to by the stage it was given when it first diagnosed. In certain cases, after a period of remission a doctor might restage the cancer, but this does not happen very often. If the cancer is given a recurrence or retreatment stage, the same process that was done when the cancer was first diagnosed will be repeated: exams, imaging tests, biopsies, and possibly surgery. The new stage will be recorded with a lower case "r" before the recurrence or retreatment designation.
