The below is helpful but not a stand alone type statistic or characteristic of your PSA.
- I have a friend whose free PSA was very high indicating a low probability of prostate cancer and ….all of his twelve cores showed cancer, however all the cores were Gleason’s 6.
- The free PSA (being very low) was what prompted me to “get off the fence” and do a biopsy..so in that regard it sometimes is that extra shove in the reluctant patient.
- I have had patients with a low free PSA and no cancer.
In general the chart below indicates that you have a higher chance of having prostate cancer on a biopsy if your free PSA is low, and vice versa if it is high, but again this is not fool-proof and should only be “one of the arrows in your prostate decision-making quiver.”
PSA Scale/ Partin table
PSA is an enzyme produced by the prostate gland. Normally, very little PSA enters the blood. Therefore, high levels of PSA in the blood can be an indicator of prostate cancer. However, other factors can lead to high levels of PSA including:
BPH, noncancerous enlargement of the prostate gland prostatitis, inflammation of the prostate gland recent sexual intercourse advanced age African-American or Asian race recent biopsy of the prostate gland recent digital rectal examination PSA found in the blood may be bound (attached to proteins) or free (not bound). Men with prostate cancer have a high percentage of bound PSA and a low percentage of free PSA.
Probability of detecting cancer by needle biopsy based on PSA and percentage of free PSA results:
|PSA (ng/mL)||Probability of cancer, %|
|0 – 2||~1|
|2 – 4||15|
|4 – 10||25|
To further determine the probability of cancer when PSA is in the 4-10 range, evaluate the free PSA level. The higher the percent of free PSA, the lower the probability of cancer.
|Free PSA %||Probability of Cancer, %|
|0 – 10||56|
|10 – 15||28|
|15 – 20||20|
|20 – 25||16|
*Data are for men with normal digital rectal examination results, regardless of patient age. †Normal PSA values may be less for younger men. Source: JAMA 1998; 279:1542-1547. Reprinted with permission.