The PCA3 test
A success story from laboratory to market place
The number of prostate cancer cases is increasing rapidly.
Fortunately not all these tumours need to be operated - some are slow-growing or indolent. The question remains: how do we reliably establish which tumour is aggressive and which is not? The PCA3 assay is the first gene-based diagnostic test to help solve the current challenges associated with the diagnosis of PCa.
The genetic test was developed in the laboratory of the Radboud University in Nijmegen, The Netherlands, by a team headed by Professor Jack Schalken (JS).
Currently the early detection of prostate cancer (PCa) relies primarily on digital rectal examination (DRE) of the prostate and the prostate specific antigen (PSA) concentration in the blood. The outcome of both tests can result in a prostate biopsy to confirm the diagnosis of PCa. Each of these three measures has shortfalls that contribute to an increasing number of unnecessary biopsies, which are unpleasant for the patient. PCA3 (Prostate CAncer gene 3) is a tool available in a simple urine test to help make better biopsy decisions in the diagnosis of PCa.
The final answer – is the PCA3 test an improvement for screening for prostate cancer - will have to come from an ongoing study. At the moment a screening study is being done in Rotterdam to compare the value of PCA3 tests with PSA tests. The results should be published in 2009.
The PCA3 test means a breakthrough in the diagnosis of prostate cancer, since it is more specific for aggressive tumours. How much more specific is it?
JS: ‘The PCA3 test has a specificity of over 80%, while the specificity of PSA testing is 25%. The PSA test is not at all selective for aggressive cancers while the cancers PCA3 detects are aggressive in 85% of cases.
‘It is also a sensitive test. The tumours that were missed had a Gleason score of six or less (a score that is given to prostate cancer based upon its microscopic appearance; cancers with a higher Gleason score are more aggressive and have a worse prognosis). 10% of missed cancers had a score of seven and were still fairly small. The test would probably have picked them up at a later stage.’
Will the PCA3 test be further refined or developed?
JS: ‘No, the test is fully developed. It can, however, be the basis for a marker panel. Tumour markers are chemical substances that are produced by some cancers. Most of these substances can be found in the urine or bloodstream in small amounts, even when cancer is not present. When cancers produce these substances, they are usually produced in very large amounts. In the next two to three years, additional markers will be added that give more information about the presence of a significant cancer.
‘Molecular testing is going through revolutionary developments. In five years’ time, PCA3 testing may well be available as a point-of-care test, which means it can be done as a bedside test. This will have an enormous impact on the logistics and efficiency of any clinic; the patient comes in, gives urine and shortly after that you know the PCA3 value. The team can then immediately decide which treatment to offer the patient.’
The PCA3 test has been on the market for a while. Why was the promotion low key?
JS: ‘This is a new and rather complex tool that should remain in the hands of experts for at least the first few years.
‘There are eight labs specialised in molecular diagnostics in Europe that provide this test. The tests are rather expensive and it takes qualified personnel to perform them. Thus, for reasons of quality, efficiency and costs it is best to have these tests done in specialised laboratories. I am convinced that this is the future for advanced diagnostics.’
Do you think this type of testing should be part of the national healthcare systems? Is it reimbursed at the moment?
JS: ‘Reimbursement is an issue; it is different in every European country. However I am convinced that this is transient. The value of the test is such that it will get a place in the diagnostics reimbursement system. We should lobby more, both in Brussels and in local countries, to inform politicians of how important diagnostics can be. Less than 2% of the overall healthcare budget is spent on laboratory diagnostics, which is why people are less concerned about it. Diagnostics can, however, have a vast impact on treatment.’
Source: European Association of Urology
01.03.2009
