In the United States, prostate cancer is the second most commonly diagnosed cancer (after skin cancers) and the third most common cause of cancer-related deaths in men. Approximately 1 in 7 men will be diagnosed with prostate cancer in his lifetime. It is estimated that 161,360 men will be diagnosed with prostate cancer and 26,730 will die of the disease in the United States in 2017. Prostate cancer is more common in older men than younger men and is more likely to occur in men with a family history of prostate cancer and men of African American ancestry. Prostate cancer is a heterogeneous disease with tumors ranging from indolent to very aggressive. Survival differs according to disease stage at diagnosis. Approximately 91% of prostate cancers are discovered in the local or regional stages, for which the 5-year relative survival rate approaches 100%. Men with malignant prostate cancer that has spread to parts of the body remote to the primary tumor have a 5-year survival rate of approximately 30%.
Prostate cancer can be identified in asymptomatic men by routine screening, which includes measuring the amount of prostate-specific antigen (PSA) in blood and physical examination via digital rectal examination (DRE). When initial testing results are suspicious for prostate cancer, a prostate biopsy is typically performed using a transrectal ultrasound (TRUS) for guidance. Standard prostate biopsy involves the removal of 12 small cylinders (called cores) of tissue from different parts of the prostate. Pathological evaluation of the cores is used to diagnose prostate cancer. If prostate cancer is detected, a primary grade is assigned to the predominant pattern and a second grade is assigned for the second most common pattern.The sum of the primary grade and second grade is the Gleason score, with a higher Gleason score corresponding to a worse prognosis. Although biopsy is considered the standard to diagnose prostate cancer, it can miss prostate cancer if the section of the prostate with cancer was not biopsied.
Screening and treatment for prostate cancer is controversial and carries with it the potential for overdiagnosis and overtreatment, as many prostate cancers grow very slowly and affected men often die of other causes before the cancer becomes symptomatic. One cause of diagnosis of clinically insignificant prostate cancer is use of PSA as a screening technique. The biggest limitation of PSA is lack of specificity for prostate cancer, as many other benign conditions—such as benign prostatic hypertrophy (BPH), prostatitis, instrumentation, and trauma—can lead to increased PSA levels. This lack of specificity leads to unnecessary biopsies and diagnosis of indolent prostate cancer. PSA levels > 4.0 nanograms per milliliter (ng/mL) are commonly used as a threshold for prostate biopsy, although age-specific upper reference limits have been created and adjusted according to ethnicity. However, approximately 65% to 70% of men with an increased PSA ranging from 4 to 10 ng/mL have a negative prostate biopsy, and up to 15% of men with prostate cancer have PSA levels < 4 ng/mL. In fact, in 2012, the U.S. Preventive Services Task Force (USPSTF) recommended against PSA-based screening for prostate cancer, although the USPSTF is in the process of updating the recommendations and may recommend clinicians to discuss the potential benefits and harms of PSA-based screening in men aged 55 to 69 years.
The identification of biomarkers that are more sensitive to detecting prostate cancer and differentiating between clinically significant prostate cancer and indolent disease are needed, especially in the gray zone of PSA 4 to 10 ng/mL. Different blood-based and urinary biomarkers as well as molecular classifiers have been developed. One blood-based example is the Prostate Health Index (PHI), which combines 3 different isoforms of PSA into a mathematical formula to identify patients who should move forward with a prostate biopsy. This report examines the published evidence regarding the Beckman Coulter PHI for prebiopsy triage.
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