A case control study of sarcosine as an early prostate cancer detection biomarker

Background: Sarcosine has been investigated as a prostate cancer biomarker with mixed results concerning its predictive power. We performed a case-control evaluation of the predictive value of serum sarcosine for early detection in a population-based cohort of men undergoing prostate-specific antigen (PSA) screening. Methods: For analysis we used 251 cancer cases and 246 age-matched non-cancer cases from the San Antonio Biomarkers Of Risk (SABOR) screening study. For cancer cases, pre-diagnostic serum was utilized for sarcosine measurement. Controls were defined as men who had been followed at least for 5 years on study with no prostate cancer diagnosis; sarcosine was measured on the initial baseline serum. HPLC-electrospray ionization mass spectrometry was used for serum sarcosine quantification. The association of sarcosine with prostate cancer was assessed using area underneath the receiver-operating characteristic curve (AUC), and logistic regression adjusting for PSA, digital rectal exam, family history, age, race, and history of a prior negative biopsy. Among cancer cases, nominal logistic regression was used for the association of sarcosine with Gleason grade. Results: Sarcosine levels were overlapping between the prostate cancer cases (median 15.8 uM, range 6.2 to 42.5 uM) and controls (median 16.2 uM, range 6.4 to 53.6 uM). The AUC of sarcosine was not statistically different from random chance either for participants with any PSA value (52.2 %) or those with PSA values in the range of 2 to 10 ng/mL (54.3 %). Sarcosine was not predictive of Gleason score and added no independent predictive power to standard prostate cancer risk factors for detection of prostate cancer (all p-values > 0.05). Conclusions: Serum sarcosine should not be pursued further as a marker for the early detection of prostate cancer.