Clinical staging is an important component of the initial evaluation. Clinical stage refers to the extent of the disease and as such influences decision making because it indicates how far the disease has progressed and how likely a treatment may be able to control it. Other components of the initial evaluation include two readily available clinical diagnostic variables: the PSA level and the Gleason score from the prostate biopsy. Often, these variables are combined to give the probability of the progression of disease.
Prostate Cancer Staging: How Does it Work?
Staging is a term that is used to determine if a cancer has spread from where it first began. Prostate cancer staging is commonly described as:
Localized prostate cancer: the cancer is contained within the prostate gland and has not spread to nearby tissues or elsewhere in the body.
Locally advanced prostate cancer: the cancer has spread outside the prostate gland to surrounding tissue, most often the seminal vesicles.
Advanced prostate cancer: the cancer has spread to nearby lymph nodes, bones, or elsewhere in the body.
“They determine the grade by looking under a microscope to see how aggressive the cells look, and depending on the psa (prostate-specific antigen) of the grade, they may or may not do additional tests,” Dr. Delworth says. “Those tests are usually either a bone scan or a CT scan - and that’s to determine if there’s any spread.”
Tools used for this purpose include predictive, validated nomograms. Such nomograms provide information regarding the likelihood that the disease is confined to the prostate gland, spread locally beyond the prostate gland, or spread distantly into lymph node tissue or elsewhere in the body. Many patients have a heightened appreciation of their prostate cancer risk profile by accessing nomograms and then entering in their own clinical variables to get a sense of the “big picture.”
The most common form of prostate cancer is adenocarcinoma (greater than 95%). This type of prostate cancer is a malignant transformation of the structure of glands and the cells that make up these glands into a random and disorganized architecture. Prostate cancer tissue can be evaluated under the microscope to identify this transformation. The pathologist’s microscopic evaluation of the prostate cancer tissue also determines the aggressiveness level, referred to as the Gleason score. The Gleason score represents the sum of two numbers rating the two most common patterns of abnormal glandular architecture based on a graded scale of 1 to 5, with 1 indicating low-grade cancer and 5 indicating high-grade cancer. The first number corresponds with the predominant pattern and the second number relating to the second most common pattern observed in examining the prostate tissue for an individual patient. For example, a Gleason score of 4 + 3 = 7 indicates a predominant pattern of mostly abnormal glands that are not quite the highest grade with a secondary pattern that is somewhat less. In cases where the glands are abnormal but still fairly uniform in appearance, the same number may be repeated.
Tumor aggressiveness increases with the score (e.g., 4 + 4 is more aggressive than 3 + 4).
When doctors refer to cancer staging they are talking about the extent to which the cancer has spread. Both “clinical staging” and “pathological staging” are frequently used, but it is important to recognize the difference between them.
Clinical staging refers to the determination of the extent of disease based on clinical findings prior to any sort of treatment. This primarily involves the findings from the digital rectal examination. Digital rectal examination assesses whether the tumor is palpable and the extent to which this seems to involve the prostate. Because the prostate is a bilobar structure, the examiner can comment on whether the tumor is minimally or extensively palpable, and if it involves one or both sides of the prostate. This palpation involves only the zone of the prostate that borders on the rectal wall, and this side of the prostate is called the peripheral zone.