Last April we reported on activities related to the development of a test known as the Prostate Health Index (PHI or phi), which has been tested for its potential as a tool to better identify men at risk for clinically significant prostate cancer as compared to men with potentially indolent disease.
In May 2010, Catalona et al. presented additional data at the annual meeting of the American Urological Association, and the full text of the report on their prospective, multi-center trial of PHI in 892 men has just been published online in the Journal of Urology (see Catalona et al. for the abstract.)
Based on the full report, it is apparent to us that the absolute clinical value of the PHI test is still to be determined. While it offers statistically significant results when applied to large numbers of men, its value as a meaningful indicator of risk for a specific individual is much less clear. The authors’ carefully worded conclusion to their paper states that, “The PHI measurement, … may be useful to decrease unnecessary biopsies with improved specificity at various sensitivities for [prostate cancer] detection in men 50 years or older with PSA 2.0 to 10.0 ng/ml and negative DRE findings” [bold italic type added for emphasis].
It is important to appreciate that this multicenter trial of the PHI test only encompassed the role of the test up to and including the results of a prostate biopsy in men considered to be at potential risk for prostate cancer. We have no real idea (as yet) whether the test can accurately identify men who can be confirmed as high risk based on the outcomes of a radical prostatectomy.
The degree to which levels of the [-2]pro-prostate specific antigen (2pPSA), which is a key component of the PHI test, can be used to help identify risk for either prostate cancer in any form or aggressive forms of prostate cancer in particular is still being studied. The concern of The “New” Prostate Cancer InfoLink is whether the extensive attempts to better use data from PSA isoforms and bound and free PSA in different types of tissue is really going to get us to any test that can truly differentiate between indolent and aggressive forms of this disease, or whether we would be better advised to look at very different areas of research in order to identify such discriminatory tests.