Cancer cells grow and divide without control or order and often form a mass of tissue called a tumour. As a tumour grows, it can invade nearby tissues and organs. The stages of cancer is based on knowledge of the way the cancer progresses (spread).

What is meant by staging?

Staging describes the severity of a person’s cancer when it was first diagnosed. On average, the higher the stage, the worse the cancer’s effect on the person who has it. Staging is important for the following reasons:

    • It helps the doctor plan the appropriate treatment
    • It can be used in estimating a person’s prognosis
    • Knowing the stage of cancer is important in identifying clinical trials that may be a suitable treatment option for a patient
    • It gives health care providers and researchers a common terminology for evaluating and comparing the results of clinical trials.

What types of tests are used to determine stage?

The types of tests used for staging depend on the type of cancer. Tests include the following:

    • Physical exams are used to gather information about the cancer
    • Imaging studies produce pictures of areas inside the body. These studies are important tools in determining stage
    • Laboratory tests are studies of blood, urine, other fluids and tissues taken from the body
    • Pathology reports may include information about the size of the tumour, the growth of the tumour into other tissues and organs, the type of cancer cells, and the grade of the tumour
    • Surgical reports tell what is found during surgery.

Common elements of staging systems

Staging systems for cancer have evolved over time and continue to change as scientists learn more about cancer. There are different kinds of staging systems; some staging systems cover many types of cancer, others focus on a particular type. The common elements considered in most staging systems are as follows:

    • Site of the primary tumour and the cell type
    • Tumour size and/or extent (reach)
    • Regional lymph node involvement (the spread of cancer to nearby lymph nodes)
    • Number of tumours (the primary tumour and the presence of metastatic tumours, or metastases)
    • Tumour grade (how closely the cancer cells and tissue resemble normal cells and tissue).

Summary staging

Many cancer registries use “summary staging”. This system is used for all types of cancer and it groups cancer cases into five main categories:

    • In situ (Stage 0). This is used to describe cancer in situ, which literally means “in place”. Stage 0 cancers are still located in the place they started and have not invaded nearby tissues. This stage of cancer is often highly curable, usually by removing the entire tumour with surgery
    • Localised (Stage I). This is usually a small cancer or tumour that has not grown deeply into nearby tissues and has not spread to the lymph nodes or other parts of the body. It is often called early-stage cancer
    • Regional spread (Stages II and III). These stages indicate cancers or tumours that are larger in size, have grown more deeply into nearby tissue and have spread to lymph nodes, but not to other parts of the body
    • Distant (Stages IV). This stage means that the cancer has spread to other organs or parts of the body. It is also called advanced or metastatic cancer
    • Unknown. There is not enough information to determine the stage.

TNM staging system

Another tool doctors use to describe a cancer’s stage is the TNM system. This system examines three factors: the size and location of the tumour (Tumour, T); whether cancer cells have spread to the lymph nodes located near the tumour (Node, N); and whether the tumour has spread to other parts of the body (Metastasis, M). The results are then combined to determine the stage of cancer for each person. The TNM system is mainly used to describe cancers that form solid tumours like breast, colon, and lung cancers.

 

Sources
http://www.cancer.gov/cancertopics/factsheet/detection/staging
http://www.cancer.net/all-about-cancer/treating-cancer/stages-cancer