Colorectal Cancer (Bowel Cancer) Symptoms, Screening and Diagnosis
The stage of a cancer tells you its size and whether it has spread. It helps determine how serious the cancer is and which treatments are best.
The method your clinician is most likely to use to determine the stage of your colorectal cancer is the TNM staging system. The TNM staging system stands for tumour, node and metastases.
- T describes the size of the tumour (cancer)
- N describes whether there are any cancer cells in the lymph nodes. Lymph nodes are small, bean-shaped collections of immune cells. Many types of cancer often spread to nearby lymph nodes before they reach other parts of the body.
- M describes whether the cancer has spread to a different part of the body
Your doctor gives each letter (T, N and M) a number, depending on how far the cancer has grown.
These numbers are explained in the table below.
|T (TUMOUR)||The extent (size) of the primary tumour|
How far has the cancer grown into (or outside) the wall of the colorectal or rectum?
|TX||The tumour can’t be measured.|
|T0||There is no evidence of a primary tumour (it cannot be found).|
|Tis||The cancer cells are only growing in the most superficial layer of tissue, without growing into deeper tissues. This may also be called in situ cancer or pre-cancer.|
|T1, T2, T3, and T4||Numbers after the T (such as TI,12,13, and T4) might describe the tumour size and/or amount of spread into nearby structures.|
|N (NODES)||The spread to nearby lymph nodes|
Has the cancers spread to nearby lymph nodes?
|NX||Means the nearby lymph nodes cannot be evaluated.|
|N0||Means nearby lymph nodes do not contain cancer.|
|N1, N2, N3, and N4||Numbers after the N (such as N1, N2, and N3) might describe the size, location, and/or the number of nearby lymph nodes affected.|
|M (METASTASIS)||The spread (metastasis) to distant sites|
Has the cancer spread to distant lymph nodes or distant organs?
|M0||Means that no distant cancer spread was found.|
|M1||Means that the cancer has spread to distant organs or tissues (distant metastases were found).|
The TNM staging system
The T, N and M assessments will be combined to create one overall series of letters and numbers to indicate your TNM staging. For example, Tis N0 M0 would indicate that the cancer cells are only growing in the most superficial layer of tissue, the nearby lymph nodes do not contain cancer, and the cancer has not spread.
The stages of colorectal cancer
During surgery, the primary tumour and certain lymph nodes are removed.
After examination of the removed tumour under the microscope, the pathologist will determine the pathological staging with an exact (final) interpretation of the depth of invasion into the bowel wall and the number of lymph nodes involved with the tumour.
Once the values for T, N, and M have been determined, they are combined to assign an overall stage. For most cancers, the stage is a Roman numeral from 0 to IV, where stage 0 is the lowest and IV (4) is the highest. As a rule, the lower the number, the less the cancer has spread. A higher number, such as stage IV, means cancer has spread more. And within a stage, an earlier letter means a lower stage – for example, stage IIIB is lower than stage IIIC.
The stage of your cancer determines the prognosis, which refers to the outlook of your cancer: the lower the stage the better the outlook.
Determining the stage is fundamental in order to make the right decision about the treatment.
An illustration of stage I colorectal cancer; The square drawing on the right shows the different parts of the wall of the colon or rectum in detail. In stage I, tumour cells are located in the mucosa and submucosa (this example); they may also be found in the muscle layers. However, tumour cells are not found beyond the muscles layers – to the serosa or lymph nodes.
The different stages of colorectal cancer are shown in the table below.
|STAGE 0||The cancer has not grown beyond the first layer of the colorectal wall; it is non-invasive cancer.|
|STAGE I||The cancer has grown into either the second or third layer of the colorectal wall, but there is no cancer in nearby or distant sites.|
(can be more specific divided in 11A or 118)
|The cancer has grown into the fourth layer of or the outside of the colorectal wall; there is no cancer nearby or distant sites.|
|STAGE III||The cancer has spread from the colorectal to nearby lymph nodes or there are small secondary tumours within the colorectal.|
|STAGE IV||The cancer has spread to distant organs such as the liver or lungs.|