Updated project metadata. Updated publication reference for PubMed record(s): 23991666. To explore plasma biomarkers complementing the specificity of PSA test, we developed a unique proteomic technology QUEST-MS (Quick Enrichment of Small Targets for Mass Spectrometry). The QUEST-MS method based on 96-well formatted sequential reversed phase chromatography allowing efficient enrichment of < 20 kDa proteins quickly and reproducibly. The LC/MS/MS data from 24 healthy controls, 19 benign prostate hypertrophy (BPH) patients, and 73 prostate cancer patients plasma were subjected to label-free quantification analysis on Expressionist proteome server. Data processing: Mascot Server 2.3.1 was used with the database SwissProt 2011_08 (531473 sequences,188463640 residues). Enzyme: semiTrypsin. Search parameters: Peptide Mass Tolerance : +- 3 ppm, Fragment Mass Tolerance:+-0.8 Da. Fixed modifications:Carbamidomethyl (C). Variable modifications:Oxidation (M),Deamidated (NQ). Max Missed Cleavages:2.