Prostate cancer develops in a man’s prostate gland, located below the bladder, near the rectum and around the urethra. It is responsible for the production of a fluid that is expelled in sperm during ejaculation. Prostate cancer develops when the cells in the prostate grow out of control, instead of dividing and dying like the healthy cells.
Symptoms of prostate cancer include urinary problems, such as a slow or weak urinary stream or the need to urinate more often, especially at night; blood in the urine; erectile dysfunction; pain in the hips, back , ribs, or other areas where the cancer may have spread to the bones, and weakness or numbness in the limbs.
Symptoms in early cases of the disease may not be noticeable, so diagnosis can be difficult. To confirm a diagnosis, physicians ask about a patient’s medical history and perform a complete physical exam. Additional diagnostic tests include prostate-specific antigen (PSA) blood test, transrectal ultrasound (TRUS), and prostate biopsy. After the diagnosis, it is important that physicians determine the stage or extent of the prostate cancer, which is used to determine treatment options and predict a patient’s outlook.
Prostate Cancer Staging Systems
The predominantly used staging system for prostate cancer is the American Joint Committee on Cancer (AJCC) TNM system, which is a standard method for a cancer care team to describe how far a cancer has spread. To determine the stage of the prostate cancer, physicians evaluate the extent of the primary tumor (T category), whether the cancer has spread to nearby lymph nodes (N category), the absence or presence of distant metastasis (M category), the PSA level at the time of diagnosis, and the Gleason score, based on the prostate biopsy (or surgery).
“There are actually two types of staging for prostate cancer,” according to the American Cancer Society. “The clinical stage is your doctor’s best estimate of the extent of your disease, based on the results of the physical exam (including DRE), lab tests, prostate biopsy, and any imaging tests you have had. If you have surgery, your doctors can also determine the pathologic stage, which is based on the surgery and examination of the removed tissue. This means that if you have surgery, the stage of your cancer might actually change afterward (if cancer was found in a place it wasn’t suspected, for example).”
Therefore, pathologic staging may be more accurate than clinical staging, since physicians can observe the extent of the cancer. This explains the advantages of radical prostatectomy surgery, when compared to radiation therapy or active surveillance.
In addition to the TNM system, there are also other systems used to stage prostate cancer. The Whitmore-Jewett system stages prostate cancer as A, B, C or D, and it was common in the past, but it has fallen into disuse. The D’Amico system is more common to calculate the risk of prostate cancer to spread outside the prostate; it is not used for all patients with prostate cancer, dividing the cases into low, intermediate, and high.
Stages of Prostate Cancer Development
Stage 1 prostate cancer is the equivalent to T1 or T2a, which refers to a tumor that cannot be felt or seen with imaging or a cancer that is in one half or less of only one side of the prostate. The cancer is still within the prostate and has not spread to any nearby lymph nodes (N0 and M0), the Gleason score is under six, and the PSA under 10.
The second category is divided into stage 2A and stage 2B. Stage 2A refers to N0 and M0 as well. In the case of T1, the Gleason score is seven and the PSA level under 20, or the Gleason score is under six and the PSA is between 10 and 20. In the case of T2a or T2b, which means that the cancer is in one half, less or more, of only one side (left or right) of the prostate, the Gleason score is seven or less and the PSA level lower than 20.
Stage 2B refers to three different situations. The first is T2c, which means that the tumor can be felt by digital rectal exam or seen with imaging such as transrectal ultrasound and is in both sides of the prostate, as well as N0, M0, any Gleason score, and any PSA. It also applies to T1 or T2, N0, M0, any Gleason score, and PSA of 20 or more or either T1 or T2, N0, M0, Gleason score of 8 or higher, and any PSA.
Stage 3 prostate cancer is diagnosed when “the cancer has grown outside the prostate and may have spread to the seminal vesicles [T3], but it has not spread to nearby lymph nodes [N0] or elsewhere in the body [M0]. The tumor can have any Gleason score and the PSA can be any value.”
In addition, stage 4 refers to a cancer that has grown into tissues next to the prostate, other than the seminal vesicles, including the urethral sphincter, rectum, bladder, or the wall of the pelvis (T4), as well as N0, M0, any Gleason score, and any PSA.
Other situations that mean stage 4 prostate cancer include any T, M0, any Gleason score, any PSA, and N1, the equivalent to cancer spread to nearby lymph nodes, or any T, any N, any Gleason score, any PSA, and M1, which means that the cancer has spread to other, more distant parts of the body.
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