When a person is diagnosed with cancer, the doctor(s) inform him about the stage to which the cancer has progressed. 'Cancer Staging' is nothing but a process of determining the size and spread of cancer.
Staging information is important for a doctor to be able to plan treatment and also to predict a person’s outlook (prognosis). Although each person’s situation is different, cancers with the same stage tend to have similar outlooks and are often treated the same way.
There are two types of staging:
1.) Clinical Staging and 2.) Pathological Staging & There are two types of staging sytems:
1.) Numbered System and 2.) TNM System
These staging system are used for most forms of cancer, except brain tumors and hematological malignancies.
TYPES OF STAGING
1.) Clinical Staging- This is an estimate of the extent of the cancer based on test results before a surgery like physical examinations, imaging tests (x-rays, CT scans, etc.), tumor biopsy, endoscopy, blood tests, etc. This stage is the baseline used for comparison when looking at how the cancer responds to treatment.
2.) Pathological Staging-
Pathologic stage adds additional information gained by examination of the tumor microscopically by a pathologist after it has been surgically removed.
TYPES OF STAGING SYSTEMS
1.) The Numbered System
It uses numbers to denote how far the cancer has progressed.
Stage 0 Cancer- This stage describes cancer in situ, which means “in place.” Stage 0 cancers are still located in the place they started and have not spread to nearby tissues. This stage of cancer is often highly curable, usually by removing the entire tumor with surgery. Stage I Cancer- This stage is usually a small cancer or tumor that has not grown deeply into nearby tissues. It also has not spread to the lymph nodes or other parts of the body. It is often called early-stage cancer. Stage II and Stage III Cancers- These 2 stages indicate larger cancers or tumors that have grown more deeply into nearby tissue. They may have also spread to lymph nodes but not to other parts of the body. Stage IV Cancer- This stage means that the cancer has spread to other organs or parts of the body. It is also called advanced or metastatic cancer.
2.) TNM stands for T umour, N ode, M etastasis. This system describes the size of the initial cancer (the primary tumour), whether the cancer has spread to the lymph nodes, and whether it has spread to a different part of the body (metastasised). The system uses letters and numbers to describe the cancer:
Tumour (T) refers to the size of the cancer and how far it has spread into nearby tissue. The letter "T" plus a number (0 to 4) describes the size and location of the tumor, including how much the tumor has grown into nearby tissues. Tumor size is measured in centimeters (cm). For some types of cancer, lowercase letters, such as “a,” “b,” or "m" (for multiple), are added to the “T” category to provide more detail.
T: size or direct extent of the primary tumour (such as T1, T2, T3 and T4. Numbers after T describe the size and spread of tumour. 1 being small and 4 being large).
Tx: tumour cannot be assessed
Tis: carcinoma in situ
T0: no evidence of tumour
Node (N) refers to whether the cancer has spread to the lymph nodes – it can be between 0 (no lymph nodes containing cancer cells) and 3 (lots of lymph nodes containing cancer cells).
NX means the nearby lymph nodes cannot be evaluated.
N0 means nearby lymph nodes do not contain cancer.
Numbers after the N (such as N1, N2, and N3) might describe the size, location, and/or the number of nearby lymph nodes affected by cancer. The higher the number after N, the greater the cancer spread to nearby lymph nodes.
Metastasis (M) refers to whether the cancer has spread to another part of the body – it can either be 0 (the cancer hasn't spread) or 1 (the cancer has spread).
So for example, a cancer that has spread to the lymph nodes but not metastasized may be T3N1M0. A bigger tumour that has affected lymph nodes and has spread to other parts of the body may be T4N3M1.
In the TNM system, clinical stage and pathologic stage are denoted by a small "c" or "p" before the stage (e.g., cT3N1M0 or pT2N0). A "y" prefix suggests stage assessed after chemotherapy and/or radiation therapy; in other words, the individual had neoadjuvant therapy.
An "r" prefix is for recurrent cancer.
The other factors that are taken into account before finally deciding the stage are- Grade, Cell-type, Tumour Location and Tumour Marker Levels.
Other staging systems
Some cancers grow and spread in a different way and therefore not all cancers are staged using the TNM system. The TNM system is mainly used to describe cancers that form solid tumors, such as breast, lung cancer, etc. For other cancers doctors use different staging systems for e.g.:
Central nervous system tumors (brain tumors)- Because cancerous brain tumors do not normally spread outside the brain and spinal cord, only the "T" description of the TNM system applies. Currently, no single staging system exists for central nervous system tumors.
Childhood cancers- Childhood cancers are not staged using the TNM system. Doctors stage most childhood cancers separately according to other staging systems that are often specific to the type of cancer.
Cancers of the blood- The TNM system does not describe leukemia, lymphoma, or multiple myeloma since they usually do not form solid tumors. Each blood cancer has a unique staging system.
A cancer’s stage does not change
The stage of a cancer is determined only at the time of the cancer being diagnosed (or immediately after that). This stage does not change over time, even if the cancer shrinks, grows, spreads, or comes back after treatment. The cancer is still referred to by the stage it was given when it was first found and diagnosed, although information about the current extent of the cancer is added (and of course, the treatment is adjusted as needed).
For example, let’s say a person is first diagnosed with stage II colon cancer. The cancer goes away with treatment, but then it comes back and spreads to the bones. The cancer is still called a stage II colon cancer, now with recurrent disease in the bones.
If the colon cancer did not go away with the original treatment and spread to the bones it would be called a stage II colon cancer with bone metastasis. In either case, the original stage does not change and it’s not called a stage IV colon cancer. Stage IV colon cancer refers to a cancer that has already spread to a distant part of the body when it’s first diagnosed.
Restaging
Sometimes, a doctor might “restage” a cancer to determine how well a treatment is working or to get more information about a cancer that has come back after treatment. This process uses the same staging system described above. Usually some of the same tests that were done when the cancer was first diagnosed will be repeated. After this, the doctor may assign the cancer a new stage. The doctor then adds a lowercase “r” before the new stage to show that it is different from that of the first diagnosis. However, this is not common.
