Stages of prostate cancer

As with other forms of cancer, the prognosis for prostate cancer depends on how far the cancer has spread at the time it’s diagnosed. Doctors describe this spread using a system of classification called staging.

Prostate cancer stages can be complex and difficult to understand. Below are the different stages and what they mean to you.

Prostate cancer stages: growth and spread

Prostate cancer grows locally within the prostate gland, often for many years. Eventually the cancer extends beyond the prostate. Prostate cancer can spread outside the prostate gland in three ways:

• By growing into neighbouring tissues (invasion)
• By spreading through the lymph system of lymph nodes and lymph vessels
• By travelling to distant tissues through the blood (metastasis)

Prostate cancer stages describe the precise extent of prostate cancer’s spread.

Tests to identify prostate cancer stage

After a prostate cancer diagnosis, tests are done to detect how the cancer has spread, if it has, outside the prostate. Not all men need every test. It depends on the characteristics of a man’s prostate cancer, as seen in a biopsy. Tests to help determine the stage of prostate cancer include:

• Digital rectal examination (using a gloved finger)
• Prostate-specific antigen (PSA, a blood test)
• Transrectal ultrasound
• MRI (magnetic resonance imaging) of the prostate using a rectal probe
• CT (computerised tomography) scan of the abdomen and pelvis, looking for prostate cancer metastasis to other organs
• MRI of the skeleton, or a nuclear-medicine bone scan, to look for metastasis to the bones
• Surgery to examine the lymph nodes in the pelvis for any prostate cancer spread

The TNM system of prostate cancer stages

As they do with most cancers, doctors use the TNM system of prostate cancer stages. The stages are described in terms of three different aspects of tumour growth and spread: tumour, nodes and metastasis:

• T - for tumour - Describes how large the main area of prostate cancer is.
• N- for nodes - Describes whether the prostate cancer has spread to any lymph nodes, and to what extent.
• M - for metastasis - Means the distant spread of prostate cancer, for example to the bones or liver.

There are other ways of classifying prostate cancer such as the Gleason grading system. Sometimes the TNM system, the Gleason score and results from a DRE and PSA tests are combined to describe the stage of prostate cancer as a simple number:

Prostate cancer stage I

In stage I, prostate cancer is found in only the prostate. Stage I prostate cancer is microscopic: it cannot be felt in a digital rectal examination (DRE) and it isn’t seen on imaging of the prostate gland.

Prostate cancer stage II

In stage II, the tumour has grown inside the prostate but hasn’t extended beyond it.

Prostate cancer stage III

Stage III prostate cancer has spread outside the prostate, but only marginally. Prostate cancer in stage III may involve nearby tissues such as the seminal vesicles.

Prostate cancer stage IV

In stage IV, the cancer has spread (metastasised) outside the prostate to other tissues. Stage IV prostate cancer commonly involves the lymph nodes, bones, liver or lungs.

Accurately identifying the prostate cancer stage is extremely important. It helps to determine the optimal treatment, as well as the prognosis for the disease. For this reason it’s worth going through extensive testing to get the correct prostate cancer stage.