Urine protein test represents novel biomarker for prostate cancer
MedWire News: UK researchers have identified a novel urinary biomarker for the detection of prostate cancer.
Measurement of the minichromosome maintenance (Mcm) 5 protein is simple, noninvasive, and accurately discriminates between prostate cancer cases and healthy patients, they say in the British Journal of Cancer.
"There is an urgent need for more accurate, noninvasive diagnostic testing for prostate cancer," write Gareth Williams, from University College London, and colleagues.
The team argues that the traditionally used tumor marker, prostate-specific antigen (PSA), is not ideal because PSA levels can also be elevated in other prostatic diseases, whereas "Mcm5 detection can be regarded as a cancer-specific test."
Mcm5 has previously been shown to be overexpressed in prostate cancer, note the researchers, who calculated levels of the urinary protein in 88 men with prostate cancer, 28 men with no evidence of the disease (strictly normal control group), and an extended control cohort of 331 men with a benign final diagnosis, regardless of PSA measurements.
The team also examined the effects of prostate massage on Mcm5 levels in the urine of 55 men from the prostate cancer cohort, and the overall discriminative ability of Mcm5 as a marker of disease.
The highest median Mcm5 signal level among the strictly normal control group was measured by immunoassay at less than 1800 cells per well. The equivalent measurement in the prostate cancer group was significantly higher, at 3560 cells per well.
Using the maximum Mcm5 value obtained for each patient (either pre- or post-massage), the overall sensitivity of the test to detect prostate cancer was high, at 82% (72 out of 88 cancer cases), as was the specificity among the strictly normal controls, at 93% (26 out of 28).
In the extended control cohort, the median Mcm5 signal was also significantly lower than among cancer cases, at less than 1800 cells per well, and specificity remained high, at 73%.
Williams et al found that prostate massage led to a significant increase in the median Mcm5 signal measured, from 2360 to 3440 cells per well, and also a significant increase in diagnostic sensitivity, from 60% to 82%.
They do warn, however, that although the study identifies Mcm5 as a novel biomarker for prostate cancer detection, "it is not yet clear whether the test will be able to specifically identify clinically significant cancers."
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By Sarah Guy