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How do doctors diagnose prostate cancer?
Prostate cancer is diagnosed based on a combination of signs and symptoms and a variety of tests.
Signs and symptoms
Tests to screen for prostate cancer
Tests to confirm the diagnosis of prostate cancer
Signs and symptoms
Like most cancers, early prostate cancer is typically without any symptoms. In fact, most prostate cancer diagnosed today is found by an abnormal prostate specific antigen (PSA) blood test, long before there are any symptoms at all.
Advanced prostate cancer can produce back pain, and can also affect urine flow by causing obstruction. These symptoms include decreased urine flow and increased urine frequency. However, the most common cause of problems with urine flow is benign prostatic hypertrophy, or BPH, which affects the central portion of the prostate gland. Therefore, symptoms are simply unreliable in the diagnosis of prostate cancer, especially when the cancer is in the early, curable stage.
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Tests to screen for prostate cancer
The two most important tests for prostate cancer can detect it early, before it produces symptoms. They are:
- The digital rectal examination: This is done by a physician, who inserts his gloved finger into the rectum, feeling the prostate gland for masses or hard spots.
- Prostate specific antigen (PSA): This is a blood test that measures a substance released by the prostate gland into the circulation. All men have a small amount of circulating PSA; the level rises in prostate cancer and sometimes in BPH. The "normal" value for PSA varies with age and ethnicity.
The National Cancer Institute and the American Urologic Association recommend that both digital rectal exam and blood PSA levels be performed annually on all men over 50. The evidence is mounting that prostate cancer can be cured in its early stages, and for this reason, early diagnosis through PSA screening is promising. Some authorities recommend that African American men begin annual testing at 45, because of their higher risk. Not all medical groups agree with these recommendations. Some argue that screening for prostate cancer must be very carefully individualized on a patient-by-patient basis. A national, randomized clinical trial is currently under way to help clear up this controversy. Unfortunately, the results will not be available for several years. In the meantime each patient and his primary care physician should evaluate the benefits and potential risks of screening.
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Tests to confirm the diagnosis of prostate cancer
A biopsy of the prostate gland, which can be done in a doctor's office, confirms the diagnosis of prostate cancer.
After it has been diagnosed, prostate cancer is then graded and staged. The grade of a prostate cancer refers to the aggressiveness of the cancer. The Gleason scale grades prostate cancer on a scale of 1 to 10. A Gleason grade of 1 to 4 is low grade, 5 to 7 is intermediate, and 8 to 10 is high grade, the most aggressive, with the worst prognosis.
The stage of prostate cancer refers to spread of the disease. Some doctors list the stages as A, B, C, and D, while others refer to I, II, III, and IV. In A/I or B/II, the cancer is contained within the prostate gland. In Stage C/III, it has spread outside the gland, but remains in the general vicinity of the gland. In Stage D/IV, it has spread to distant parts of the body, such as the bone.
Stage and grade are used to help patients and their doctors get a sense of how much cancer a patient has and how aggressive the cancer may be. However, these are very crude indicators of how advanced the cancer is or how quickly it is likely to grow. The stage is very subjective (based on a physician's impression of a rectal exam). Although less subject to variation than stage, the Gleason's score too is somewhat variable, based on a pathologist's interpretation of biopsy material.
Furthermore, the advent of PSA screening has made "stage" based on a rectal exam far less important then it used to be. That is because most men diagnosed with prostate cancer today have no palpable disease. In fact, numerous studies have shown that the value of the PSA at the time of diagnosis gives more prognostic information than either grade or stage. Patients with low PSA (10 or less) seem to do very well, those with higher PSA (10-20) less well, and those with very high PSA (greater than 20) poorly. This is called "biochemical" staging.
Current and future research will seek to improve screening methods to make them more sensitive and better able to indicate treatment options and predict long-term prognosis.
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