Circulating Biomarkers for the Early Diagnosis of Gastrointestinal Cancers

Gastrointestinal (GI) cancer is a particularly sobering disease because it carries a high mortality rate. The characteristic tendency of GI cancers to reveal symptoms only in the malignant phase is the major contributing factor to its poor patient outcomes. Hence, it is critical to actively work towards identifying methods to diagnose this type of cancer in its early stages. Over the last decade, there has been robust research into identifying methods to detect GI cancers in their early stages with a particular emphasis on circulating biomarkers for this purpose. The present report is a review compounded from over 140 research papers on the emerging influence of circulating biomarkers in this regard. Circulating biomarker-based diagnosis via liquid biopsy offers several advantages over traditional diagnostic methods, such as colonoscopy, because the method is noninvasive; it can be used to monitor tumor load with respect to medication; and it can be used to predict recurrence. This review is largely divided into two relevant subtopics: biomarkers to diagnose gastrointestinal neuroendocrine tumors and genetic biomarkers used to diagnose common GI cancers. We focus on DNA-based biomarkers and the associated epigenetic dysregulation seen in these cancer types. Research into this area is urgently needed, and through this review chapter, the reader will gain a broad understanding of the various current uses of circulating biomarkers for both early diagnosis and prognosis of GI cancers.