How is the staging of prostate cancer done?

The staging of a cancer refers to determining the extent of the disease (where in the body have the prostate cancer cells spread). Once a prostate cancer is diagnosed on a biopsy, additional tests are done to assess whether the cancer has spread beyond the gland.

Radionuclide bone scans can determine if there is a spread of the tumor to the bones. The radioactive substance highlights areas where the cancer has affected the bones. This test is usually reserved for men with prostate cancer who have deep bone pain or a fracture or who have biopsy findings and high PSA values (>10-20 ng/ml) suggestive of advanced or aggressive disease.

Chest X-ray can be used to detect whether or not cancer has spread to the lungs. Ultrasound tests can be used to look for the effects of a urinary blockage on the kidneys. This study can also be used to assess the bladder for any sign of urinary obstruction due to prostate enlargement by looking at the thickness of the bladder wall as well as the amount of urine remaining within the bladder after an attempt at passing urine.

Additionally, CT scans (coaxial tomography) and MRIs (magnetic resonance imaging) can determine if the cancer has spread to adjacent tissues or organs such as the bladder or rectum or to other parts of the body such as the liver or lungs. Newer scanning using a method called PET scan can sometimes help to detect hidden locations of cancer that has spread to various areas of the body.

Cystoscopy is usually performed in selected situations. A thin, flexible, lighted tube with a tiny camera on the end is inserted through the urethra to the bladder. The camera transmits images to a video monitor. This may show whether the cancer has spread to the urethra or bladder and may be utilized to take a biopsy from these organs.

To summarize, doctors do the staging of prostate cancer based primarily on the results of the prostate biopsy, possibly other biopsies, and imaging tests. In staging a cancer, doctors assign various letters and numbers to the cancer, depending on which of the classifications for staging they use. The numbers and letters in the different classifications define the volume or amount of the tumor and the spread of the cancer. The stage of the prostate cancer, therefore, helps to predict the expected course of the disease and determine the choice of treatment.

The stages of prostate cancer are categorized as follows:

• Stage I (or A): The cancer cannot be felt on a digital rectal exam, and there is no evidence that it has spread outside the prostate. These are often found incidentally after surgery for an enlarged prostate.
• Stage II (or B): The tumor is larger than a stage I and can be felt on a digital rectal exam. There is no evidence that the cancer has spread outside the prostate. These are usually found on a biopsy when a man has an elevated PSA level.
• Stage III (or C): The cancer has invaded other tissues neighboring the prostate.
• Stage IV (or D): The cancer has spread to lymph nodes or to other organs.

Most doctors currently use the 2002 TNM (Tumor, Node, Metastases) staging system for prostate cancer. This is based on a combination of three criteria: extent of the primary tumor (T stage), involvement of lymph nodes by the cancer (N stage), and the presence or absence of spread to distant areas of the body in the form of metastasis (M stage). The TNM 2002 staging system is as follows:

Evaluation of the (primary) tumor ("T")

• TX: The primary tumor cannot be evaluated.
• T0: There is no evidence of tumor.
• T1: Tumor is present but not detectable clinically or with imaging.
• T1a: Tumor was incidentally found in less than 5% of prostate tissue resected (for other reasons).
• T1b: Tumor was incidentally found in greater than 5% of prostate tissue resected.
• T1c: Tumor was found in a needle biopsy performed due to an elevated serum PSA.
• T2: The tumor can be felt (palpated) on examination but has not spread outside the prostate.
• T2a: The tumor is in half or less than half of one of the prostate gland's two lobes.
• T2b: The tumor is in more than half of one lobe, but not both.
• T2c: The tumor is in both lobes.
• T3: The tumor has spread through the prostatic capsule (if it is only partway through, it is still T2).
• T3a: The tumor has spread through the capsule on one or both sides.
• T3b: The tumor has invaded one or both seminal vesicles.
• T4: The tumor has invaded other nearby structures.

It should be stressed that the designation "T2c" implies a tumor which is palpable in both lobes of the prostate. Tumors which are found to be bilateral on biopsy only but which are not palpable bilaterally should not be staged as T2c.

Evaluation of the regional lymph nodes ("N")

• NX: The regional lymph nodes cannot be evaluated.
• N0: There has been no spread to the regional lymph nodes.
• N1: There has been spread to the regional lymph nodes.

Evaluation of distant metastasis ("M")

• MX: Distant metastasis cannot be evaluated.
• M0: There is no distant metastasis.
• M1: There is distant metastasis.
• M1a: The cancer has spread to lymph nodes beyond the regional ones.
• M1b: The cancer has spread to bone.
• M1c: The cancer has spread to other sites (regardless of bone involvement).