From the Guidelines
Free Prostate-Specific Antigen (PSA) is a crucial biomarker for evaluating prostate health and detecting prostate cancer, particularly when used in conjunction with total PSA to calculate the free PSA ratio or %fPSA. The role of free PSA in prostate cancer detection is to help differentiate between benign conditions and cancer, especially when total PSA levels are in the "gray zone" of 4-10 ng/mL 1. A higher percentage of free PSA (typically above 25%) suggests benign conditions like benign prostatic hyperplasia (BPH), while lower percentages (below 10-15%) indicate a higher risk of prostate cancer 1. Some key points to consider when using free PSA include:
- The Prostate Cancer Prevention Trial (PCPT) demonstrated that 15% of men with a PSA level of ≤4.0 ng/mL and a normal DRE had prostate cancer diagnosed on end-of-study biopsies 1
- Approximately 30% to 35% of men with serum PSA between 4 to 10 ng/mL will be found to have cancer 1
- Total PSA levels >10 ng/mL confer a greater than 67% likelihood of prostate cancer 1
- Biomarkers like percent free PSA, 4Kscore, or phi can be used to further define the probability of high-grade cancer in patients who have never undergone biopsy or after a negative biopsy 1. The use of free PSA, alongside other clinical information such as digital rectal examination findings, patient age, prostate volume, and family history, can help reduce unnecessary biopsies while improving detection of clinically significant prostate cancers 1.
From the Research
Role of Free PSA in Evaluating Prostate Health
- Free Prostate-Specific Antigen (PSA) is a valuable tool in the distinction between prostatic cancer (PCa) and benign prostatic hyperplasia (BPH) 2
- The FPSA/TPSA ratio is the method of choice for discriminating BPH and PCa, with a ratio of ≤ 15% indicating a higher likelihood of PCa 2
- Combined serum measurement of FPSA and TPSA is of particular interest in the early diagnosis of PCa for patients with non-suspicious digital rectal examination and a TPSA value between 2.5 and 10 ng/ml 2
Free PSA in Detecting Prostate Cancer
- Adding percent free PSA to total PSA improves prediction of clinically significant prostate cancer and fatal prostate cancer 3
- Percent free PSA is associated with clinically significant prostate cancer, with a decrease in percent free PSA indicating a higher risk of PCa 3
- Free PSA can be used to risk-stratify screening and decrease unnecessary prostate biopsies 3
Clinical Applications of Free PSA
- Free PSA can be used to detect early-stage but clinically significant cancers in men with a total PSA value between 2 and 4 ng/mL and normal DRE findings 4
- Percent free PSA can be used to identify men at high risk for prostate cancer who may benefit from biopsy, even with a normal total PSA and digital rectal examination 4
- Biomarkers such as percent free PSA, prostate health index (PHI), and the 4K score can be used to increase specificity and reduce the number of unnecessary biopsies 5