Staging is the procedure of determining where the tumour is located, whether it has spread or not, and how it grows. Doctors consider many factors while assessing the cancer stage.

Doctors use diagnostic tests to discover the cancer's stage, so staging may not be complete until all tests are.

TNM staging system

The TNM system is the tool doctors use to describe the stage of Bladder cancer.

• T is for tumour - How large the tumour is and where is its location
• N is for nodes - Has cancer spread to lymph nodes, and if so, where and how many?
• M is for metastasis - Whether cancer has metastasized to other parts of the body.

There are five stages of NPC: stage 0 (zero) and stages I through IV (1 through 4). The stage provides a standard way of describing cancer, so doctors can work together to plan the best treatments.

Recently, doctors have found that finding out whether the Epstein-Barr virus is present can be useful in staging.

Tumour (T)

TX - The primary tumour cannot be evaluated.

Tis - This describes a stage called carcinoma in situ. This is a very early cancer where cells are found only in 1 layer of tissue.

T0 (T plus zero)- No evidence of a tumour is found, but lymph nodes in the neck are positive for EBV.

T1 - The tumour has not spread beyond the nasopharynx. Or the tumour has grown into the oropharynx or nasal cavity but does not involve the areas around the pharynx.

T2- The tumour extends into the soft tissue of the middle throat.

T3 - The tumour extends into a bony structure or the area behind the nose.

T4 -The tumour extends inside the head to an area of the brain or into the lower part of the throat.

Node (N)

For people with NPC, doctors examine lymph nodes in a triangle-shaped area formed by 3 points:

• Where the collarbone joins the tip of the shoulder.
• The point where the neck meets the shoulder.
• Where the front half of the collarbone meets the base of the neck.

NX - The regional lymph nodes cannot be evaluated.

N0 (N plus zero) - There is no evidence of cancer in the regional lymph nodes.

N1 - Cancer has spread to lymph nodes above the triangular area detailed above. The lymph nodes are on the same side of the neck as the primary tumour. Cancer in the lymph nodes is 6 centimetres (cm) or smaller. A centimetre is roughly equal to the width of a standard pen or pencil.

N2 - Cancer has spread to lymph nodes on both sides of the neck, above the triangular area, but the cancer is 6 cm or smaller.

N3 - Cancer found in lymph nodes is larger than 6 cm or in lymph nodes located in the triangle.

Metastasis (M)

The "M" in the TNM system describes whether cancer has spread to other parts of the body, called distant metastasis.

M0 (M plus zero) - Cancer has not spread to other parts of the body.

M1- Cancer has spread to other parts of the body.

Cancer stage grouping

Doctors assign the cancer stage by combining the T, N, and M classifications.

Stage 0 - A carcinoma in situ with no spread to lymph nodes and no distant metastasis (Tis, N0, M0).

I Stage - A small tumour with no spread to lymph nodes and no distant metastasis (T1, N0, M0).

Stage II - There is evidence of EBV in lymph nodes in the neck or a tumour found only in the nasopharynx that has spread to lymph nodes but no metastasis (T0 or T1, N1, M0). This stage may also describe a tumour that has extended beyond the nasopharynx but has not spread to lymph nodes or distant parts of the body (T2, N0, M0). It may also describe a tumour that has spread to lymph nodes but has not spread elsewhere (T2, N1, M0).

Stage III - A noninvasive or invasive tumour has spread to lymph nodes on both sides of the neck above the triangular area but has not metastasized (T0, T1, or T2; N2; M0). This stage may also describe a larger tumour with or without lymph node involvement and no metastasis (T3; N0, N1, or N2; M0).

Stage IVA describes any invasive tumour with either no lymph node involvement or spread to only a single same-sided lymph node but no metastasis (T4, N0 or N1, M0). It is also used for any invasive tumour with more significant lymph node involvement but no metastasis (T4, N2, M0). It also describes any tumour (any T) with extensive lymph node involvement but no metastasis (T, N3, M0).

Stage IVB describes any tumour with evidence of distant spread (any T, any N, M1).

Recurrent - Recurrent cancer is cancer that has come back after treatment. If cancer returns, there will be another round of tests to know the extent of the recurrence. These tests and scans are usually similar to those at the original diagnosis.