In 2015, a review by Huddy et al. [156] established that POC techniques had already been used for patient screening for gastrointestinal cancer through the detection of constituents like fecal occult blood, calprotectin, volatile organic compounds (hexanoic acid, phenol, methyl phenol, and ethyl phenol), pyruvate kinase isoenzyme type M2 (M2-PK), circulating tumor cells, and DNA biomarkers like SEPT9 and tumor protein (p53). Here, TP53 is linked to neoplasm.