The detection of prostate cancer has been revolutionized by the prostate specific antigen (PSA) test. This test has enabled doctors to detect prostate cancer at a very early stage, even before symptoms occur.
The prostate specific antigen is a small protein molecule produced by the glands of the prostate that normally joins the seminal fluid. In men without prostate cancer, this antigen cannot be detected or is at a very low level in the blood stream, but becomes persistently elevated in prostate cancer.
Other noncancerous conditions can cause elevation of PSA, but usually only modestly or temporarily. This is why most doctors will repeat the PSA at least once if it is found to be high. Intermediate elevations in PSA in the range of 4 to 10 ng/ml should be sent to a urologist for consultation. Further elevations above 10 ng/ml should be referred to a urologist for thorough evaluation and biopsy.
A small proportion of prostate cancers (5 percent to 10 percent) are not associated with elevated PSA levels, but may show up as an abnormality on rectal examination. Therefore, PSA and rectal examination are complementary; either method by itself is not sufficient.
If cancer is diagnosed, it is graded on how aggressive it appears. This score is useful since it gives the doctor an idea of the prognosis and the degree to which the cancer may have spread. The score may therefore influence the recommended treatment. A score of 2 is the lowest and the best, while 10 is the highest and indicates the worst prognosis.
The PSA level is also useful in indicating the aggressiveness of the prostate cancer. The higher the PSA, the higher the likelihood that the cancer already has spread outside the gland. Therefore, a high score (more than 6) and a high PSA level (more than 20 to 30) make it very likely that the cancer has extended outside of the prostate gland, which has important implications for both treatment and prognosis.
The cancer also will be assigned a clinical stage. There are several staging systems in use, but the most commonly used assigns prostate cancer to Stage T1 through T4 (T4 being the worst prognosis). T1 and T2 cancers are confined to the prostate, while T3 indicates spread outside of the prostate to the nearby areas, and T4 indicates spread to distant areas or other major organs. An older, but also commonly used system assigns Stage A and B to cancers still located within the prostate, Stage C to spread outside the prostate, and Stage D to those cancers which have spread to distant areas, such as the bones. The doctor may order other tests, such as bone scans, X-rays, magnetic resonance imaging (MRI) or computed axial tomography (CT) scans, to better assign the clinical stage or determine the best treatment.