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PSA: How low should it go?

PSA: How low should it go?

PSA: How low should it go?

Updated: 12/22/2015

When it comes to prostate cancer follow-up, physicians may need to rethink the term undetectable. After radical prostatectomy, they usually focus on the value 0.1 ng/ml, which is the threshold for undetectable PSA.

Recent advances in technology have made it possible to measure PSA at much lower levels. In fact, Alan W. Partin, M.D., Ph.D., Daniel W. Chan, Ph.D., and Lori Sokoll, Ph.D., have been working with a company called Quanterix to develop a new, ultrasensitive PSA test called AccuPSA. This test is 1,000 times more sensitive than standard PSA tests.

Study Explores AccuPSA Test

During one study, Dr. Partin and his colleagues examined blood samples from 31 patients whose PSA level had been undetectable for at least five years after radical prostatectomy. All these patients had PSA levels less than 0.1 ng/ml after surgery. However, one third of them later had biochemical recurrence, while the others continued to have an undetectable PSA level for many years after surgery. The study participants were similar in age and race and had negative surgical margins after surgery. Interestingly, patients whose PSA levels went up had a greater presurgical PSA, clinical and pathological stage and Gleason grade than the men whose levels remained very low.

When the investigators tested the samples with AccuPSA, they found that at three months after surgery, all patients who ultimately had a rise in PSA had an AccuPSA level of 0.003 ng/ml or greater. By standard measures, this number would be considered undetectable. Among patients whose PSA levels never went back up, 75 percent had AccuPSA levels less than 0.003 ng/ml.

Initial Findings Reveal New PSA Threshold

In addition to this pilot study, larger tests are needed to confirm the results. These initial findings suggest that you could have an AccuPSA test three months after surgery. If your PSA level is less than 0.003 ng/ml, you could be confident that all your cancer has been removed. On the other hand, if your PSA level is greater than 0.003 ng/ml, you might choose to be monitored more closely for PSA recurrence in the immediate years following your surgery.


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