Fecal volatile organic compounds for early detection of colorectal cancer: where are we now?

IntroductionThe fecal volatolome, which is composed of fecal volatile organic compounds (VOCs), seems to hold potential as non-invasive biomarker for the detection of colorectal cancer (CRC) and its precursor lesions advanced adenomas (AA). The potential of the fecal volatolome has been subject of various studies using either chemical analytical or pattern-recognition techniques. The available literature on the potential of the fecal volatolome as CRC and AA biomarker was reviewed.MethodsA systematic literature search was conducted in PubMed, Embase, the Cochrane Library, Google Scholar and ResearchGate using the following keywords: Colorectal Cancer, Advanced Adenoma, Volatile Organic Compound, Metabolome, Gas Chromatrography-Mass Spectrometry, Selected-Ion Flow-Tube Mass Spectrometry, eNose, and Fecal Biomarkers.ResultsEighty-eight titles or abstracts were identified from the search, of which 11 papers describing the potential of the fecal volatolome for CRC detection were selected. In these studies, different techniques were used for the headspace analyses of fecal VOCs, limiting the possibility to compare outcomes. Increased levels of amino acids and short chain fatty acids, and decreased levels of bile acids and polyol alcohols in the gas phase of feces were observed repeatedly. All selected papers reported high diagnostic value for the detection of both CRC and AA based on fecal VOCs.ConclusionBased on the included studies, fecal VOC analyses seem promising for future screening of CRC and AA, with potentially improved test performances allowing for earlier detection of AA and CRC and consequently earlier initiation of treatment, possibly reducing morbidity and mortality rates next to lower rates of (unnecessary) colonoscopies.