Tyrosine and tryptophan in urine as biomarkers for prostate cancer: A validation study

Prostate cancer (PCa) is a common male malignancy and early diagnosis is crucial for successful treatment. The current study aims to validate results from a pilot study that demonstrated an inverse association between urine tyrosine and tryptophan levels and the severity of PCa. This study comprised a cohort of 97 patients with benign prostatic hyperplasia, 93 patients diagnosed with localized PCa, 75 patients diagnosed with locally advanced PCa, and 68 patients diagnosed with metastatic PCa. The tyrosine and tryptophan levels in the samples were analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and electrochemical sensors in accordance with the pilot to maintain uniformity for accurately evaluating the data. One-way ANOVA with post Tukey test as well as the Wilcoxon Rank Sum Test were performed. Analyzing 333 patients across PCa stages with consistent methods, we observed no significant differences in tyrosine and tryptophan levels between PCa patients and controls, finally rejecting the use of tyrosine and tryptophan as PCa biomarkers. We did, however, verify the strong correlation between the urinary concentrations of tyrosine and tryptophan found in the pilot study.