Annual Meeting, American Association of Clinical Chemistry, Illinois, Amerika Birleşik Devletleri, 27 - 31 Temmuz 2014, cilt.60, ss.7
Recently, articles regarding the role of sarcosine -a metabolite of methionine- in the diagnosis of prostate cancer have been published, but the results of these articles are inconclusive, due to different analytical approaches and type of samples used. We aimed to determine the diagnostic performance of sarcosine levels in the urine supernatants in our patient cohort.
The patients were selected amongst men who applied to Marmara University Education and Research Hospital Urology Department and were decided to undergo prostate biopsy. Serum folate, vitamin B12, PSA, fPSA were analysed. Three molecules with the same molecular mass (Alanine, beta-alanine and sarcosine) and methionine levels in urine were determined by propyl chloroformate derivatization and ESI ionization in a quadrupolar LC-MS/MS (Zivak Technologies, Turkey). Diagnostic sensitivity, specificity and AUC of PSA, %fPSA, and urinary sarcosine were calculated from ROC curve analyses.
There were 29 biopsy positive and 76 biopsy negative patients. There were no significant difference in folate, vitamin B 12, PSA, fPSA, methionine, sarcosine, alanine and beta-alanine levels between two groups. Only % fPSA was significantly decreased (20.6 ± 8.6 vs 14.4 ± 7.8; p=0.001) in the biopsy positive group. The sensitivity, specificity and AUC of urinary sarcosine (58.6 %, 55.3 % and 0.609) were lower than corresponding PSA (65.5 %, 57.9 % and 0.622, respectively) and % fPSA (58.6 %, 80.2 % and 0.707, respectively) values .
When the biopsy positive patients were grouped according to their Gleason score as < 7 (n=15) and ≥ 7 (n=14); only PSA and urinary sarcosine levels were found to be significantly higher in the ≥ 7 group, whereas % fPSA had lost its discriminatory power. When the specificities of each marker at the cut-off value where their sensitivity reached 90 % were compared, the specificity of sarcosine (19.5 %) was lower than PSA (22.4 %) and % fPSA (38.2 %).
We conclude that, urinary sarcosine levels were not useful in the diagnosis of prostate cancer in our cohort, but that it can be used to detect prostate cancer cases with a Gleason score ≥ 7. Overall, %fPSA was found to be more specific than PSA in the diagnosis of prostate cancer.