Best Test to Diagnose Prostate Cancer
The definitive diagnosis of prostate cancer requires a prostate biopsy, which should be performed when there is an abnormal digital rectal examination (DRE) and/or elevated prostate-specific antigen (PSA) level. 1
Initial Diagnostic Approach
- PSA testing combined with DRE provides the most effective screening approach for detecting prostate cancer that may require biopsy confirmation 1, 2
- PSA is more sensitive than DRE alone, detecting 82% of prostate cancers compared to 55% for DRE 3
- The American Urological Association no longer recommends a single threshold value of PSA to prompt prostate biopsy; instead, the decision should be based on multiple factors including patient age, family history, ethnicity, prior biopsy history, and comorbidities 2
Prostate Biopsy Indications
- Prostate biopsy should be offered to men suspected to have clinically significant prostate cancer, such as those with an abnormal DRE and/or elevated serum PSA 1
- The decision to proceed with biopsy should occur after counseling the patient regarding both risks and benefits 1
- Biopsy should be performed under transrectal ultrasound (TRUS) guidance, with a minimum of eight cores obtained 1
Role of Transrectal Ultrasound (TRUS)
- TRUS alone is not recommended as a primary screening tool 4
- TRUS is primarily used to guide the biopsy procedure rather than as a standalone diagnostic test 1
- TRUS is more costly and does not add appreciable detectability when both DRE and PSA results are normal 4
PSA Considerations
- Age-specific reference ranges for PSA should be considered when interpreting results 2
- It is essential to use the same PSA assay for longitudinal monitoring as PSA assays are not interchangeable 2
- Several factors can affect PSA levels including prostatitis, BPH, urethral/prostatic trauma, and medications like finasteride and dutasteride 2
Diagnostic Efficiency
- When used in combination, PSA and DRE have a higher cancer detection rate (5.8%) than either PSA (4.6%) or DRE (3.2%) alone 3
- The positive predictive value is 32% for PSA and 21% for DRE 3
- When parallel testing was examined (one or more tests being abnormal), the most efficient combination was when DRE was suspicious or serum PSA > 4 ng/ml (sensitivity = 95%) 5
Common Pitfalls
- Relying solely on TRUS findings could miss up to 40% of tumors; biopsy should be considered if either PSA is elevated or DRE is suspicious, even with normal TRUS findings 3
- Overdetection and overtreatment remain significant concerns with PSA screening, and men should be informed of these risks before proceeding to biopsy 1, 2
- Laboratory variability in PSA testing can range from 20-25% depending on standardization method 2