What affects the Prognosis of Oral Cancer?
All you know by now, the sooner it is detected the better and I really do mean the better.
There are a number of factors that influence the prognosis. The main three are:
- Tumour (T). The size and extent of the tumour. Larger lesions have a poorer prognosis.
- Distant metastasis (M). If the tumour has spread to distant sites away from the primary tumour, then it becomes increasingly difficult to treat and is more life threatening. We know it is bad when the cancer has spread- this is the reason why.
- Node involvement (N). The presence of metasis at local lymph nodes is very important. 5-year survival rate with no node involvement is about 60% but with node involvement this drops to just 25%, so only 1 in 4 patients would be expected to live beyond 5 years.
These are the three factors used in the TMN system throughout the world to classify the stage of the cancer or its severity (1-4). The stage of the cancer is used to provide a prognosis and help in choosing the most appropriate treatment for survival.
It works because cancers tend to progress in a predictable way, that is, they enlarge by invading the surrounding tissues (cells), then break away (mestastisi) travelling via the lymphatic system to the lymph nodes and finally metastasis enter the blood stream and lodge in distant sites.
The course is predictable but the speed that this happens is quite variable.
A stage I cancer is less than 2cm in size and has not yet spread anywhere.
A stage IV cancer means that the tumour is large (over 4cm) and has spread not just to the local lymph nodes, but also distant sites.
The 5 year survival of a stage I cancer is 69%. For stage IV for it is just 8% and you wonder why I keep talking about early detection and cancer prevention!
- Grading. Staging is one way to grade a cancer (the most important); grading is another- it tells you the likely speed at which the cancer will progress from stage to stage. Some cancers are more aggressive than others. When looked at under a microscope, we can tell by the level of differentiation (how much the cancer resembles the normal tissue), as to whether the cancer is likely to grow slower or faster and produce metastasis sooner or later.
- Men. The prognosis for males tends to be worse than females.
- Site. The further back you go in the mouth, the worse the prognosis becomes. This is highlighted by the following 5 year survival rates:
(i) Lip 77.5%
(ii) Floor of the mouth 30%
(iii) Tongue 26%
(iv) Oral pharynx 17.6%