PSA Levels and Prostate Cancer Staging
What Is Prostate Cancer?
Prostate cancer is one of the most common types of cancers in men. The prostate gland, which exists only in men, is involved in the production of semen. Cancer in the prostate usually grows very slowly and often remains within the gland.
In some instances, it can become aggressive and spread beyond the prostate, in which case treatment is needed. For the best prognosis, doctors need to detect the cancer, use a stage scale to determine how aggressive it is, and implement the best treatment plan.
The prostate gland makes a protein called prostate-specific antigen, or PSA. A healthy man without prostate cancer should have a small amount of PSA circulating in his blood.
Some conditions related to the prostate can cause the gland to produce more PSA than normal. These include prostatitis, benign prostatic hyperplasia (enlarged prostate), and prostate cancer.
The PSA Test
A PSA test is a test that measures the levels of the protein in the blood. The results are typically given in nanograms of PSA per milliliter of blood (ng/mL). A measurement of 4 ng/mL is considered to be normal, but this baseline changes with age. As a man ages, his PSA levels naturally rise.
PSA tests are given to screen for prostate cancer, as part of the determination of the stage of prostate cancer, and to track the progression of cancer.
Staging Prostate Cancer
Doctors stage prostate cancer to determine how advanced the disease is and to determine treatment. Stages range from I to IV, with the disease being most advanced in stage IV. There are a number of factors that go into this labeling.
Doctors examine the extent of the tumor within the prostate, whether it has spread to nearby tissue, and how far it has spread into the body. They also compare the cancer cells to normal cells to get a rating called the Gleason score. Finally, PSA levels are used to complete the picture.
The Role of PSA in Staging
PSA levels are just one clue in determining how advanced and how aggressive a case of prostate cancer is. It cannot be used alone because, although elevated PSA levels may indicate cancer, there are exceptions.
Some men who have prostate cancer do not exhibit abnormal PSA levels, and some noncancerous conditions, like an infection, can cause high PSA levels. PSA levels in the blood are one tool used for staging prostate cancer, but it does not give a complete picture.
Stage I prostate cancer is characterized by a Gleason score of less than six, restriction to one half of the prostate with no spreading to surrounding tissues, and PSA levels below ten. The Gleason score compares cancer cells to normal cells. The more the cells differ, the higher the score and the more aggressive the cancer. Like the PSA level, it is just one piece of the puzzle.
In stage IIA prostate cancer, the tumor is still restricted to one side of the prostate, but elevated PSA levels and a higher Gleason score indicate the cancer may be more aggressive than it was in stage I. The Gleason score may be up to seven, and the PSA levels are greater than ten, but less than 20 ng/mL.
By stage IIB, the tumor may have spread to the second half of the prostate gland, but it also may be still contained on one side. If the tumor is still restricted to one half of the prostate, a Gleason score of eight and any PSA level categorizes the cancer as stage IIB. If the tumor has spread to the other side, the Gleason score and the PSA level become irrelevant.
Stages III and IV
By the time prostate cancer has reached stage III or stage IV, the PSA level is considered to be irrelevant. At this point, the stage is determined by the extent of the spread of the cancer. In stage III, the tumor has grown into the tissues surrounding the prostate, and by stage IV it has spread farther, possibly even into the lymph nodes or bones.
To determine the reach of the cancer cells, doctors use imaging techniques, like CT scans, and biopsies of tissues, particularly the lymph nodes.
Controversy over PSA Levels
PSA tests are one tool used to stage prostate cancer, but as a screening tool it is controversial, and not always recommended. Research has proven that using PSA to screen for cancer does not save lives. On the other hand, it can cause harm.
A high PSA level usually leads to more invasive procedures, like biopsies or even surgery, that are not always necessary, and that can cause complications and side effects. PSA testing does remain, however, an important tool in staging and plotting the course of the disease once it is diagnosed.
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