22 december 2005: Bron: Wang X, Yu J, Sreekumar A, et al. Autoantibody signatures in prostate cancer. N Engl J Med. 2005;353:1224-1235. Met aan dr. van der Schaar die ons dit nieuws toestuurde.

Een nieuw ontwikkelde bloedtest welke 22 biowaarden/markers meet lijkt aanvullend op een PSA meting een goede en effectieve hulp bij het vaststellen van prostaatkanker. Dit bewijzen verschillende studies gedaan o.a. aan de universiteit van Michigan Medical School. De betrouwbaarheid van de gezamenlijke testen was in vergelijking met een PSA test significant veel beter. In 1 studie waren de resultaten bv. deze: 88.2% specificiek (8 van de 68 controle monsters waren vals positief) en 81.6% sensitief (11 van 60 prostaat kanker monsters waren vals negatief). Bij PSA metingen ligt de vals positieve waarde soms rond de 80%. Een groot verschil dus met deze aanvullende bloedtest.

A new blood test, which detects prostate cancer–specific autoantibodies, may be a useful adjunct to initial prostate-specific antigen (PSA) screening (P < .001), according to results from the Early Detection Research Network, an NCI initiative.

This might be useful in PSA levels of 10 ng/mL or less, enabling physicians and patients to make informed decisions about whether to proceed with biopsy, said lead researcher Arul Chinnaiyan, MD, PhD, professor of pathology at the University of Michigan Medical School.

Researchers should evaluate the 22-biomarkers to see whether conditions such as prostatitis, autoimmune disorders and other conditions confound screening results when tested against the autoimmune signatures associated with prostate cancer, Chinnaiyan and colleagues said.

Clinicians should routinely offer men PSA screening to diagnose prostate cancer. However, PSA testing for prostate cancer has a false-positive rate as high as 80%. The researchers sought to determine whether a test using autoantibody signatures could improve early detection of prostate cancer, thereby helping patients avoid unnecessary biopsies.

Using serum samples banked between 1995 and 2004 at the university’s Specialized Research Program in Prostate Cancer, they examined the blood from 158 men aged 40 and older who had biopsy-proven prostate cancer, but who had not yet undergone treatment. They also studied 159 control serum samples taken from men aged 46 to 83 without prostate cancer.

Specific and sensitive
To develop their detection system, the investigators tested 20 cancerous samples and 11 control samples against 2,304 bacteriophages that carry surface proteins. They discovered that 186 phage proteins were sensitive to the samples from men with prostate cancer.

Next, they used a training set of 129 serum samples (59 prostate cancer, 70 controls) to test against these 186 phage proteins. They found that a set of 22 biomarkers consistently distinguished the prostate cancer samples from the noncancerous controls. When applying to 128 independent validation samples (60 prostate cancer, 68 controls), the biomarkers made the distinction with 88.2% specificity (8 of 68 control samples were false positives) and 81.6% sensitivity (11 of 60 prostate cancer samples were false negatives).

This finding also indicates that the efficacy of the autoantibody profile’s ability to detect prostate cancer decreases once the factor causing the production of antigens is removed or once therapy has been initiated. Nine of 30 serum samples from men with lung cancer tested positive for prostate cancer. This suggests that the 22 prostate cancer autoantibodies react somewhat to other types of cancer.

Editor’s note: Very exciting data. Offers the potential for a substantial advance in diagnostic, prognostic and therapeutic monitoring of patients with prostate cancer. I anxiously look forward to extension and verification of these data by these and other workers. — Donald L. Trump, MD, FACP

For more information:
Wang X, Yu J, Sreekumar A, et al. Autoantibody signatures in prostate cancer. N Engl J Med. 2005;353:1224-1235.

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