Prostate cancer proteomic test: Use of biomarker panel before biopsy improves diagnoses and saves money

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  • Published: Feb 15, 2012
  • Author: Steve Down
  • Channels: Proteomics & Genomics / Proteomics
thumbnail image: Prostate cancer proteomic test: Use of biomarker panel before biopsy improves diagnoses and saves money

Inaccuracies in prostate cancer diagnosis

Prostate cancer is the most common cancer in men in many western countries with about 37,000 new cases reported annually in the UK, 218,000 in the USA and 17,000 in Australia. The number of diagnosed cases is rising year by year but this is partially influenced by the fact that men are living longer and by increased use of the prostate specific antigen (PSA) test.

In reality, many more men are affected by prostate cancer than is ever diagnosed because the disease can advance very slowly. Evidence from autopsies has revealed that at least 70% of men who died of other diseases had prostate cancer by the age of 80 but it had never been diagnosed. They were not aware of it and neither were their doctors.

In these cases, slow disease progression leaves a difficult choice. To treat or not to treat? In older men, the treatment might cause more harm than good. Of course, other prostate cancers are aggressive so surgery and various treatments are essential.

Following introduction of the main test for prostate cancer, which involves detection of PSA in urine, long-term mortality rates have fallen sharply. However, the test is notoriously inaccurate with a very high false positive rate of up to 76%. This has the consequence that a great many biopsies are carried out unnecessarily, incurring additional clinical costs and needless discomfort and stress for the patient.

The prostate biopsy itself is not completely accurate either, with reported sensitivities of 45-77%, so all in all, the diagnosis of prostate cancer leaves a lot to be desired. It is these uncertainties that prompted a team of scientists to develop a new test for prostate cancer, which was published in 2008.

The test involves the detection of a panel of 12 polypeptide biomarkers in the urine of patients using capillary electrophoresis-mass spectrometry (CE-MS) and it was validated by the analysis of the urine of 534 patients. In each case, the proteomic analysis was followed by a biopsy and the combination gave a sensitivity for prostate cancer detection of 90% and a specificity of 61%.

Since then, the same research team have applied the test in a routine clinical setting in hospital outpatient departments to see how it performs and to estimate the cost effectiveness. The results are reported in the International Journal of Urology by lead reporter Eric Schiffer who was affiliated to both Mosaiques Diagnostics GmbH, Hannover, and the BHF Glasgow Cardiovascular Research Centre, UK.

Improved patient care

A total of 211 consecutive outpatients were examined. They had been referred following digital rectal examination and/or the discovery of suspicious PSA levels. In the first instance, the first-stream urine from each patient was depleted of proteins of higher molecular mass, like albumin and immunoglobulin G, and analysed by CE-MS on a time-of-flight instrument. The 12 biomarkers ranging in molecular mass from 10054 to 43009 Da were targeted as indicators of the presence or absence of prostate cancer.

One year later, 184 patients were available for follow up examination. They underwent PSA tests, rectal examination and transrectal ultrasound scanning and those with suspicious results were subjected to prostate biopsy.

The biopsy identified prostate cancer in 49 cases, and the proteomics test correctly recognised 42 of these, which is a sensitivity of 86%. For 135 patients who tested negative for prostate cancer, 79 also gave negative results in the urinary proteome, giving a specificity of 59%. These sensitivity and specificity figures confirmed those reported in the 2008 study.

The high sensitivity of the proteomics procedure gave a high negative predictive value of greater than 90%. So, in practice, a negative result would suggest that the patient should be observed over a period with regular PSA tests rather than committing to a biopsy. The agreement between proteome analysis and follow-up testing was 66%, which is twice as good as that using a PSA test.

Schiffer suggests that the urinary proteomics test will be an attractive non-invasive method for improving the diagnostic accuracy of prostate cancer. "The test should not be considered as a novel screening test. Based on the presented data, it seems to be a reasonable diagnostic add-on for patients with positive screening PSA before submission to biopsy."

Cost effective testing

The researchers also carried out an analysis of the cost effectiveness of performing the proteomics test along with the biopsy, compared with the biopsy alone, based on the known and estimated costs of the various processes and the likely number of tests per patient.

They found that substantial cost savings could be made overall, based largely on the reduction in the number of biopsies by an estimated 49%, but also on the reduction in the number of PSA tests. There were also savings due to a reduction in complications associated with biopsy, such as inflammation or fever.

So, the practice of performing the urinary proteomics test before biopsy will limit invasive patient procedures in many cases and will reduce the financial burden on the health authority.


The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

 A diagnostic test for prostate cancer based on the urinary proteome that was devised in 2008 has been applied in the clinical setting in Germany, providing a cost effective confirmation for patients who have tested positive for prostate-specific antigen and avoiding unnecessary biopsies. 

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