Like other forms of cancer, the prognosis for prostate cancer depends on how far the cancer has spread at the time it’s diagnosed. Doctors use a system of classification called staging to describe prostate cancer’s local extent and evidence of spread.
Prostate cancer stages can be complex and difficult to understand. WebMD takes a look at prostate cancer stages and what they mean to you.
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Prostate cancer grows locally within the prostate, often for many years. Eventually, prostate cancer extends outside the prostate. Prostate cancer can spread beyond the prostate in three ways:
By growing into neighboring tissues (invasion)
By spreading through the lymph system of lymph nodes and lymph vessels
By traveling 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 seen on biopsy. Tests to help determine the stage of prostate cancer include:
Digital rectal exam
Prostate-specific antigen (blood test)
MRI of the prostate using a rectal probe
CT 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 bones
Surgery to examine the lymph nodes in the pelvis for any prostate cancer spread
The TNM System for Prostate Cancer Stages
As they do for most cancers, doctors use the TNM system of prostate cancer stages. The prostate cancer stages are described using three different aspects of tumor growth and spread. It’s called the TNM system for tumor, nodes, and metastasis:
T -- for tumor -- describes the size of the main area of prostate cancer.
N -- for nodes -- describes whether prostate cancer has spread to any lymph nodes and to what extent.
M -- for metastasis -- means distant spread of prostate cancer, for example, to the bones or liver.
There are other ways of classifying prostate cancer, such as the Gleason system. Sometimes, the TNM system and Gleason score are combined together to describe prostate cancer stage.
Prostate Cancer Stage I
In stage I, prostate cancer is found in the prostate only. Stage I prostate cancer is microscopic; it can’t be felt on a digital rectal exam (DRE), and it isn’t seen on imaging of the prostate.
Prostate Cancer Stage II
In stage II, the tumor 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 barely. Prostate cancer in stage III may involve nearby tissues, like the seminal vesicles.
Prostate Cancer Stage IV
In stage IV, the cancer has spread (metastasized) outside the prostate to other tissues. Stage IV prostate cancer commonly spreads to lymph nodes, the bones, liver, or lungs.
Accurately identifying the prostate cancer stage is extremely important. Prostate cancer stage helps determine the optimal treatment, as well as prognosis. For this reason, it’s worth going through extensive testing to get the correct prostate cancer stage.