Sarcosine in urine after digital rectal examination fails as a marker in prostate cancer detection and identification of aggressive tumours

Background: Sarcosine in urine was recently suggested to be a promising tool in prostate cancer (PCa) diagnostics.

Objective: To reevaluate sarcosine as a potential biomarker for early PCa detection and for prediction of tumour aggressiveness.

Design, setting, and participants: Sarcosine was measured in urine samples from 106 PCa patients and 33 patients with no evidence of malignancy (NEM), confirmed by 8-12 core prostate biopsies, after standardised digital rectal examination, as well as from 12 healthy men and women. The results were related to the clinicopathologic data on prostate volume, tumour stage, Gleason score, and prostate specific antigen (PSA).

Measurements: Sarcosine in urine was determined by gas chromatography-mass spectrometry using a commercial amino acid assay and was normalised to urine creatinine. Nonparametric statistical tests and receiver operating characteristics (ROC) analyses were performed to assess the diagnostic performance.

Results and limitations: The median sarcosine-creatinine ratio in urine was 13% lower in PCa than in NEM patients. Sarcosine values were not associated with tumour stage (pT2 vs pT3) or grade (Gleason score <7 vs > or = 7). ROC analyses proved that the discrimination between PCa and NEM patients was not improved by sarcosine in comparison with total PSA, but it was significantly worse than the percent free PSA. The higher proportion of PCa than NEM patients can be considered a limitation of this study.

Conclusions: Sarcosine in urine after rectal digital examination cannot be considered as a suitable marker to differentiate between patients with and without PCa.