Prostate Cancer Staging

When faced with a diagnosis of prostate cancer, remember that there are various treatment options depending on your risk group. Your risk group is based on your blood PSA levels, information gained from your prostate biopsy, as well as the cancer’s clinical stage.

Prostate cancer is categorized into four different stages of development, each indicating tumor size and how far the disease has spread. Prostate cancer’s stages are defined as follows:

Stage I or II (also called clinical stage T1 or T2): The disease is in its earliest stages and is clinically localized, meaning the cancer hasn’t spread beyond the prostate gland.

Stage III (also called clinical stage T3): The disease shows extracapsular extension, meaning the tumor has grown through the capsule surrounding the prostate and may have invaded the surrounding fat or seminal vesicles, which are adjacent to the prostate.

Stage IV (also called clinical stage T4): The disease has invaded other local organs or spread to other parts of the body.

Cancers can spread to other organs in two ways: the tumor can grow into a neighboring organ, or, more commonly, cancerous cells can get into the bloodstream or the lymphatic system (both of which transport fluids throughout the body), and the cancer cells may end up growing somewhere that may be quite far from the original tumor site. Both of these processes are known as metastasis, and these new cancer growths are called metastases or metastatic tumors. Metastatic prostate cancer is still prostate cancer, even if it has spread to a distant area of the body, and the cells still tend to resemble prostate cells to some degree.

A prostate tumor’s stage can partly be determined by a digital rectal exam. If the tumor is large and/or irregular and the physician suspects it may have spread, radiographic imaging (such as a CT scan, MRI, or bone scan) will help evaluate this possibility.

Assessing Risk

Physicians grade the aggressiveness of prostate cancer to determine the likelihood of significant risk to your life and health. This process, called risk stratification, can help you make vital decisions about your care. Your cancer will usually be rated as low-risk, medium- or intermediate-risk, or high-risk, based on the cancer’s clinical stage, your blood PSA levels, and information gained from your prostate biopsy. This assessment includes your Gleason score number of tissue samples in which cancerous cells were found, and the percentage of each of these tissue cores affected by the tumor.

Prostate cancer risk is generally categorized as follows:

  • Low-risk: A Gleason score of 6, a prostate specific antigen (PSA) level of less than 10 nanograms per milliliter (ng/ml) of blood, and a clinical stage of T2 (Stage II) or less.
  • Medium- or intermediate-risk: A Gleason score of 7, and/or PSA level between 10 and 20 ng/ml, and the cancer is at about clinical stage T2 (Stage II).
  • High-risk: A Gleason score of 8–10 and/or a PSA level higher than 20 ng/ml, and the cancer is at clinical stage T3 (Stage III) or higher.

About Gleason Score

Prostate cancer is graded using the Gleason System. Gleason grades range from 1 to 5. Grades 1 and 2 are largely no longer considered cancer, so the lowest grade one can receive on a biopsy is a Grade 3. Grade 5 is used when cancer cells are very abnormal. Prostate cancers often have areas with different grades. Therefore, a grade is assigned to the two areas that make up most of the cancer. These two grades are added to yield the Gleason Score. The first number assigned is the grade that is most abundant in the tumor. For example, in a Gleason Score of 4+3=7, most of the tumor is grade 4 and less is grade 3. If only a single Gleason grade is present in the biopsy, that number is included twice in the Gleason Score sum (e.g., if only Gleason Grade 3 is present the Gleason Score is 3+3=6). The higher the Gleason score, the more risk the cancer carries. The lowest Gleason score of a cancer found on a prostate biopsy is 6.