Sarcosine cannot predict prostate cancer aggression or recurrence
MedWire News: Levels of the metabolite sarcosine cannot reliably predict the aggressiveness of prostate cancer, nor recurrence-free survival after surgical treatment, study results show.
The findings call into question those from recent analyses that support metabolite profiling in prostate tissue, blood, and urine, to improve diagnosis and provide answers regarding tumor invasiveness, say the researchers.
"Metabolomics provides deeper insight into altered molecular pathways in cancer cases," explain Klaus Jung (Charité University Hospital, Berlin, Germany) and colleagues.
However, they add that "despite promising experimental data… our results show that sarcosine was not a prognostic marker predicting biochemical recurrence in a challenging cohort of matched organ-confined disease tissues."
The group compared sarcosine levels in paired malignant and nonmalignant tissues from 92 postprostatectomy prostate cancer patients, then correlated concentrations of the metabolite with tumor grade, Gleason score, and biochemical recurrence - defined as two prostate-specific antigen measurements of 0.2 ng/ml following undetectable levels (0.04 ng/ml or less) after surgery.
The median, normalized sarcosine ratio was a significant 7% higher in the malignant tissues compared with the noncancer samples, report Jung et al in the Journal of Urology.
However, the team found no significant differences in sarcosine levels in relation to men with tumor stage T2 versus T3 cancer, or men with Gleason score less than 7 versus 7 or greater tumors, both indicators of aggressive disease.
After receiver operating characteristic analysis, the ability of sarcosine to discriminate malignant from nonmalignant tissue gave an area under the curve score of 0.59 (out of a possible score of 1.00), indicating a poor diagnostic capability.
A total of 18 men, out of the 84 with available data, experienced biochemical recurrence after a median 18.6 months. The researchers note that patients' recurrence-free intervals decreased significantly with increasing T stage and Gleason score. However, sarcosine levels (either above or below the median) did not differ significantly in those with and without recurrence and did not show any predictive ability on multivariate analysis.
To conclude, Jung and co-authors highlight one of the disadvantages of using a "biomarker approach" to assess cancer outcomes: "Metabolic changes are essentially affected by environmental conditions such as diurnal variation, nutrition, and lifestyle," they write.
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By Sarah Guy