Plasma sarcosine does not distinguish early and advanced stages of prostate cancer

• Published in: South African medical journal Vol. 102; no. 8; pp. 677 - 679
• Main Authors: BOHM, L, SERAFIN, A. M, FERNANDEZ, P, VAN DER WATT, G, BOUIC, P. J. D, HARVEY, J
• Format: Journal Article
• Language: English
• Published: Rondebosch Health and Medical Publishing Group 01.08.2012; Health & Medical Publishing Group
• Subjects: Alanine; Alanine - blood; Analysis; Biological and medical sciences; Biological markers; Biomarkers, Tumor - blood; Care and treatment; Diagnosis; Gas Chromatography-Mass Spectrometry; General aspects; Gynecology. Andrology. Obstetrics; Health aspects; Humans; Identification and classification; Male; Male genital diseases; Medical sciences; Methods; Neoplasm Staging; Nephrology. Urinary tract diseases; Prostate cancer; Prostatic Neoplasms - blood; Prostatic Neoplasms - pathology; Sarcosine - blood; Statistics, Nonparametric; Tumors; Tumors of the urinary system; Urinary tract. Prostate gland; Urine; South Africa; Urinary system disease; Prostate disease; Tropical medicine; Advanced stage; Early stage; Malignant tumor; Male genital diseases; Prostate cancer; Cancer; Blood plasma
• ISSN: 0256-9574
• DOI: 10.7196/SAMJ.5768

Diagnosis of prostate cancer by prostate specific antigen (PSA) is error-prone and cannot distinguish benign prostatic hyperplasia (BPH) from malignant disease, nor identify aggressive and indolent types. We determined serum sarcosine (N-methylglycine) in 328 cancer patients by gas chromatography (GC)/mass spectroscopy (MS) and searched for correlations with early (stage T1/T2) and advanced (stage T3/T4) disease. Serum sarcosine of male control patients ranged from 1.7 µmol/l to 4.8 µmol/l. In prostate cancer patients, sarcosine ranged from 2.8 µmol/l to 20.1 µmol/l. Expressed as the sarcosine/alanine ratio, serum control values were 9.4 ± 5.5 x 10(-3) (mean ± SD) compared with 21.6 ± 9.0; 28.5 ± 16.6; 22.7 ± 7.7 and 22.2 ± 11.0 for patients diagnosed with T1, T2, T3 and T4 prostate tumours, respectively. The small differences between T1, T2, T3 and T4 patients were not statistically significant (p=0.51). However, the conventional PSA marker significantly correlated with T stage in these patients (r=0.63; p<0.009). The median sarcosine/alanine ratios among patients with early and advanced prostatic cancer ranged from 21.6 ± 9.0 to 28.5 ± 16.6 and were fairly constant, showing no statistically significant differences between T-stages. The results are consistent with published data in urine and serum which find differences between controls and patients with metastatic prostate cancer to be small and sarcosine to be uninformative regarding prostate cancer progression. By multi-comparison of PSA with T-stages in the same group of patients, we found significant correlations confirming the well-known merits and limitations of this marker.