April 27, 2023
Early & Accurate Prostate Cancer Detection – Why a Multi-Test Approach May Be the Best Prescription
A recent prostate cancer screening study out of Germany concluded that a Digital Rectal Exam (DRE) is not enough of a reliable screening tool by itself to provide the earliest possible detection of prostate cancer. The German study proves what urologists in the United States have long known – DRE alone is not accurate enough to be used as an effective screening tool for the early detection of prostate cancer.
A DRE examination involves the insertion of a gloved finger by a urologist into the patient's rectum to access the prostate gland. For a healthcare provider to feel a cancerous area in the prostate via DRE, cancer must have grown large enough to be palpable. When a cancer tumor grows large enough to be felt under the finger, it has most likely progressed to a higher stage or higher grade (i.e., more aggressive) of prostate cancer. Therefore, the rate of false negatives (prostate cancer that was present but too small to be felt by the finger) is too high for DRE to be a standalone screening test for early-stage prostate cancer detection.
Currently, the Prostate Specific Antigen (PSA) blood test is the best available screening tool for early detection of prostate cancer. PSA will pick up nearly 80% of all early-stage prostate cancers, even those with an otherwise "normal" DRE. However, PSA also has a high false positive (indicates the presence of prostate cancer when no cancer exists in the prostate) rate. This means that many men with an elevated PSA either do not have prostate cancer or clinically insignificant prostate cancer. Clinically negligible prostate cancer has a low chance of progression, a low probability of spreading, or a low chance of causing death. Because the PSA has a high false positive rate, many men with an elevated PSA will need to undergo additional and sometimes costly testing to determine whether their abnormal PSA is due to the presence of real prostate cancer.
Controversy remains over the efficacy of the PSA test. Since many men do not die of prostate cancer, even if found slightly later in their natural disease process, some argue that PSA testing does not save many lives. Some estimates indicate that thousands of PSA tests must be done to save one life. While it is agreed that PSA testing can find 5X more prostate cancers earlier than a DRE, this fact does not mean PSA testing saves 5X more lives than DRE. It does not translate to a high rate of saving lives due to the natural history of prostate cancer. Most prostate cancers grow slowly and do not result in the death of patients.
Therefore, while PSA will find cancers earlier than DRE, PSA testing does not necessarily save significantly more lives than DRE as a standalone test.
About 20% of patients with clinically significant prostate cancer may have a normal PSA but an abnormal DRE. Because DRE has a high false negative rate and PSA has a high false positive rate, combining the two tests may be complementary for patients. DRE is costless. The healthcare provider can do it during routine office visits.
It is important to note that saving life may not be the correct metric for determining the efficacy of screening tests for prostate cancer. While the death rate from prostate cancer may be low, the rate of health complications associated with advanced prostate cancer is relatively high. In other words, while a patient may not die of prostate cancer, they can still suffer significant health and quality-of-life complications from advanced prostate cancer. Such complications include but are not limited to ongoing bleeding from the urinary tract, urinary retention, pelvic pain, blood in the stool, kidney failure, a need to place kidney catheters that drain urine externally, lower extremity paralysis, chronic anemia, recurrent kidney and bladder infections, and skeletal fractures. So, while one may not die from these problems, they still pose a significant risk to overall health and quality of life. Early detection of prostate cancer by performing PSA testing combined with DRE can reduce the risk of advanced prostate cancer.
Some other modern testing modalities in the early detection of prostate cancer include an MRI of the prostate, Urine Liquid biopsy, and the 4-K blood test. However, these tests are expensive and cumbersome and are better performed as secondary tests if the PSA or DRE is abnormal.
Early prostate cancer detection is essential for men's overall health and well-being. Performing a combination of DRE and PSA tests is currently the Gold Standard for urologists in confidently assessing whether a man has prostate cancer – so that a treatment plan can be put in place sooner for the health and quality of life considerations for all patients.
Sources:
Dr. Ramin’s email answers provided on 3/7/23.
