The 'stage' of the cancer defines whether the tumour is localised to the anus or whether it has spread to the local lymph nodes (usually the groin nodes or pelvic nodes) or whether it has spread to other organs. The treating oncologist needs to know the stage to decide the most suitable treatment.
The information needed to decide the stage is gathered from both clinical examination and scanning. An examination under anaesthetic is often done to obtain the most accurate stage.
The stage is usually classified using a system called the 'TNM Staging System', where T stands for tumour, N for 'nodes' (ie lymph nodes), and M for 'metastases' (ie whether other organs are involved). Each letter is followed by a number that defines the extent of the cancer eg T2N1M0.
