Volatile Organic Compounds (VOCs) Profile in Colorectal Cancer Patients and Healthy Controls.

Volatile organic compounds (VOCs) are low molecular weight (\<1 kDa) compounds which represent the final products of cell metabolism. Their composition can be affected by several factors including diet, hormones, environment and the presence of diseases, in particular, cancer. Endogenous breath VOCs can originate anywhere in the body, reversed in the venous blood stream and than to the lung alveoli where some of them are exhaled . Alteration in VOC production in patients with cancer has been postulated to relate to (per)oxygenation of cell membrane-based polyunsaturated fatty acids resulting from genetic and/or protein mutations within tumour cells and the increased relative prevalence of reactive oxygen species within cancer cells. VOCs consist largely of benzene, alkanes and aldehydes (or their derivatives), and several studies have demonstrated that various cancers, including lung and breast cancer,melanoma, mesothelioma and hepatocellular carcinoma, are associated with specific VOC profiles that differ from normal. Volatile organic compounds are present in various excreted biological materials (urine, blood, faeces an breath) and their analysis offers a possibility for cancer screening. Colorectal cancer (CRC) is one of the commonest tumours and is an important cause of cancer-related mortality. It is the second leading cause of cancer-related death in Europe and the third in the USA. Colonoscopy is the gold standard for the diagnosis of CRC, although its cost prevents its use for mass screening. Furthermore colonoscopy is not well accepted by patients since it is an invasive exam. Faecal immunochemical blood testing (FIT) is the most widely used noninvasive screening tool, showing fairly good specificity but a high variation in sensitivity (61-91%) and adherence to screening programmes rarely reaches 50-70% of the target population. The expression of VOCs in breath that are linked to a patient's disease state could offers a powerful, non-invasive approach to identifying CRC patients.