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The most important factor that predicts survival of colo-rectal cancer is the
“Stage”, in other words how advanced the cancer is at the time of presentation.
There are two main staging systems for colo-rectal cancer, The TNM system and
the Dukes system.
The TNM takes its name from the initials of the words Tumour, Nodes,
Metastases. It is a very accurate but slightly complicated system to describe to a
lay person so we will not discuss it further here.
The Dukes system takes its name from the American pathologist who designed it
and has 4 stages.
Dukes stage A
The cancer is limited to the mucosa (the inner lining) of the bowel.
Dukes stage B
The cancer has penetrated the rest of the wall of the bowel.
Dukes stage C
The cancer, after penetrating the whole bowel wall, has spread into the lymph
nodes around the bowel. The lymph nodes receive the lymphatic vessels which
carry lymph from the bowel into the circulation. This means that a cancer with
infiltrated lymph nodes is not localised any more but has started spreading and
there is a risk that cancer cells have escaped to remote organs.
Dukes stage D
The cancer has given metastases and has spread to remote organs such as the
liver, lungs, bones etc.
The above distinction of stages is very important for 2 reasons.
Firstly, it helps to plan the treatment because as it is explained in other chapters
the treatment of colo-rectal cancer can take many different forms and protocols
depending on the individual case.
Secondly, there is a strong association between stage on presentation and
survival. Patients with Dukes A stage have a 5 year survival chance (which is
generally considered as cure) of 90%. Patients with Dukes B have 40% and
Dukes C around 20%. Patients who present with Dukes D have a less than 5%
chance of 5 year survival.
Staging