Watch out for Phi, the new prostate cancer test

The Prostate Health Index or Phi for short is making waves. And doctors, researchers, and patients are hoping that this new test will clear up the ambiguity surrounding prostate cancer testing once and for all. Is this the new prostate cancer test we are waiting for? The current testing protocol is based on the levels of prostate-specific antigens (PSA) in the blood. One of the main problems of the PSA method is the high rate of false positives that lead to unnecessary biopsy, anxiety, and even cancer treatment.

Enter Phi, a new method developed by the medical device company Beckman Coulter. The method tests for 3 different types of PSA: total PSA, free PSA, ands [-2]pro PSA in the blood serum. From these 3 values, an index called Phi ratio is calculated [Phi = (proPSA / free PSA) x (square root of PSA)]. Its advocates claim that this index is a much more precise measure of prostate cancer risk. At the annual meeting of the European Association for Urology in Barcelona last April, Phi was introduced in a symposium sponsored by Beckman Coulter and addressed the following issues:

Serum Prostate Health Index (phi) significantly increases specificity when selecting men for biopsy

Implementation of the Prostate Health Index (phi) in a prostate cancer risk assessment tool

Predicting an unfavorable outcome in men enrolled in active surveillance for prostate cancer

Supporting data were from 71 patients of John Hopkins Hospital. In these patients, researchers were able to show that Phi was correlated to unfavorable biopsy results.

Additional claims from the Barcelona symposium:

“Serum Beckman Coulter Phi is a multivariate index incorporating PSA, free PSA and [-2]proPSA concentrations into a single result to estimate the probability of cancer in men aged 50 and older with total PSA in the 2.0-10.0 ng/ml range and a non-suspicious DRE. [-2]proPSA is a novel serum marker strongly associated with prostate cancer and delivers added specificity to PSA. As a result, phi contributes to significantly reduce the number of negative biopsies resulting from suspicious PSA or %free PSA results.”

Indeed, this new test looks promising but data from large scale studies are needed to confirm its use as a more specific alternative to the standard PSA test. The annual meeting of the American Urological Association is scheduled this coming week (May 29 to June 3) in San Francisco. We will be sure to hear more about Phi at the conference.