Staging prostate cancer is a sometimes-complex process that involves multiple tests, measurements and other factors. The aim is to determine the size, extent and aggressiveness of the cancer.
There are two types of staging for prostate cancer:
. Clinical: This is based on the results of pre-surgery procedures such as a prostate-specific antigen (PSA) test, a digital rectal exam (DRE), a Gleason score (a grade based on how cancer cells behave on a micro level) and imaging tests. A doctor uses these results to determine the stage of the cancer and decide whether to recommend further diagnostic exams, such as a magnetic resonance imaging (MRI) scan.
. Pathological: This type of staging is based on information uncovered after prostate surgery. The prostate tissue is examined to get a more detailed, and sometimes more accurate, stage of the disease.
Understanding prostate cancer’s progression
To determine the appropriate treatment, doctors need to know how far the cancer has progressed, or its stage. A pathologist, the doctor trained in analyzing cells taken during a prostate biopsy, will provide two starting points—the cancer’s grade and Gleason score.
. Cancer grade: When the pathologist looks at prostate cancer cells, the most common type of cells will get a grade of 3 to 5. The area of cancer cells in the prostate will also be graded. The higher the grade, the more abnormal the cells.
. Gleason score: The two grades will be added together to get a Gleason score. This score tells doctors how likely the cancer is to grow and spread.
After a biopsy confirms prostate cancer, the patient may undergo additional tests to see whether it has spread through the blood or lymph nodes to other parts of the body. These tests are usually imaging studies and may include a bone scan, positron emission tomography (PET) scan or computed tomography (CT) scan.
Prostate cancer staging
Doctors use the results of all these tests to help determine the stage of the prostate cancer, or how far it has progressed. Widely used staging criteria is based on the TNM system developed by the American Joint Committee on Cancer.
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The three key components of the TNM system, include:
. T (tumor) describes the tumor’s size, location and how deep it has grown into the tissue.
. N (node) indicates whether cancer cells have spread to nearby lymph nodes or the channels connecting the lymph nodes.
. M (metastasis) refers to whether the cancer cells have spread to distant organs or tissue.
The stage of cancer will help doctor and patient determine the most appropriate options for treatment.
Prostate cancer stages range from I through IV.
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Stage I (stage 1) means the cancer is on one side of the prostate. Stage I cancers usually grow slowly. In this stage, the PSA level may not be high and the cancer may not be felt during a DRE. There is no lymph node involvement nor metastasis. Some cancers that are felt during a DRE may still be classified as stage I if the Gleason score is 6 or less and the PSA is lower than 10.
Stage II (stage 2) means the cancer remains confined to the prostate gland. It has three substages:
. Stage IIA: The cancer is on one or both sides of the prostate gland, the PSA blood test level is between 10 and 19, and the Gleason score is 6 or less.
. Stage IIB: The cancer is on one or both sides, the PSA is lower than 20, and the Gleason score is 7.
. Stage IIC: The cancer is on one or both sides, the PSA is lower than 20, and the Gleason score is 7 to 8.
Stage III (stage 3) means the cancer is locally advanced. The tumor has progressed and is more likely to grow and spread, with both the Gleason score and the PSA being high. This stage also has three substages:
. Stage IIIA: The cancer is on one or both sides of the prostate, the PSA is 20 or higher, and the Gleason score may be as high as 8.
. Stage IIIB: The cancer has spread outside the prostate gland to nearby tissues but not to the lymph nodes. The PSA may be any level, and the Gleason score may be up to 8.
. Stage IIIC: This stage is similar to IIIB, but the cancer may not be growing beyond the prostate and has a Gleason score of 9 or 10.
Stage IV (stage 4) means the cancer has spread to lymph nodes or to other parts of the body. It is further divided into two substages:
. Stage IVA: The cancer has spread to nearby lymph nodes but may or may not have spread to nearby tissues.
. Stage IVB: The cancer has spread to another area of the body, such as the bones or distant lymph nodes.
Prostate cancer survival
If the prostate cancer hasn’t spread to distant parts of the body (stages I to IVA), the five-year survival rate is almost 100 percent, according to the American Cancer Society. The survival rate for stage IVB is about 30 percent.