Staging of cancer

Before a decision about treatment can be made, not only the type of tumour but also its extent and distribution needs to be established. Various ‘staging investigations’ are therefore performed before a treatment decision is made. The staging systems vary according to the type of tumour

The TNM classification:

T Extent of the primary tumour

N Extent of regional lymph node involvement

M Presence or absence of metastases

Extent of primary tumour:

T0 Excised tumour

T1

T2

T3

T4 Very large tumour

Extent of regional node involvement:

N0 No nodes involved

N1

N2

N3

Presence of metastases:

M0 Not present

M1 Present

Tumour markers:

There are a number of specific tumour markers which are found in serum and are useful in diagnosis:

• α-fetoprotein – hepatocellular carcinoma, germ-cell testicular tumours
• β-human chorionic gonadotrophin (β-HCG) – choriocarcinoma
• Prostate-specific antigen (PSA) – prostate carcinoma

There are a number of other tumour markers available, but these are of little use in diagnosis. Examples include:

Carcinoma embryonic antigen (CEA) – e.g. colon cancer

Ca-125 – e.g. ovarian, gut, pancreatic cancer

Ca-19-9 – e.g. gut, pancreatic cancer

These markers are non-specific and should only be used to monitor response to treatment