MedWire News: Patients with and without prostate cancer cannot be differentiated by the levels of sarcosine in their urine following rectal digital examination (DRE), researchers report.
“Although cancer-related metabolites in urine combined with other markers are expected to become promising tools, the data for sarcosine should be interpreted with caution,” say Florian Jenztmik (University Medicine Berlin, Germany) and colleagues in the journal European Urology.
Jentzmik et al measured sarcosine levels in urine samples from 106 prostate cancer (PCa) patients and 33 patients with no evidence of malignancy (NEM), confirmed by 8–12 core prostate biopsies, after standardized DRE, as well as from 12 healthy men and women.
The researchers report that the median sarcosine–creatinine ratio in urine was 13% lower in PCa than NEM patients. This result is in contrast to the higher sarcosine levels in PCa patients reported in previous research.
“The use of the highly specific, validated sarcosine assay and the measurements of all our samples in a blinded manner with a good analytic performance support the validity of our data,” say the researchers.
Furthermore, sarcosine values were not associated with tumor stage (pT2 vs pT3) or grade (Gleason score <7 vs ≥7).
Receiver operating characteristic (ROC) analyses showed that the discrimination between PCa and NEM patients was not improved by sarcosine in comparison with use of total prostate-specific antigen (PSA), and that it was significantly worse than that achievied using percent ratio of free to total PSA (%fPSA).
Jentzmik et al report a strong correlation between sarcosine and creatinine concentrations. They say that this shows that occurrence of sarcosine in urine is due to renal excretion and is therefore unsuitable as a marker for PCa detection.
The researchers conclude: “Our data from well-defined cohorts demonstrate that sarcosine in urine after DRE is not suitable for improving the PCa diagnostic performance in comparison to routine markers such as %fPSA.”
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