Gastrointestinal (GI) cancers include a diverse range of cancers in the digestive tract organs, such as the stomach, pancreas, liver, intestine, colon, and rectum. The incidence of gastrointestinal malignancies in the world is expected to rise, due to increases in the aged population, intake of unhealthy food, and chronic diseases. These cancers not only threaten the health of the patients but are also a heavy burden on the family and wider society.

As cancer therapeutics develop, surgery to remove the malignant part of the organ has been demonstrated to be effective in curing GI tumors at an early stage. However, due to low rates of cancer screening and a lack of efficient biomarkers for early tumors, by the time the carcinogenesis of digestive organs has been diagnosed, most have reached the middle and advanced stages and have begun to metastasize, infiltrate, and spread. Fewer than 30% of patients still have the chance for surgery. Early diagnosis, identification of the driver mechanisms underlying the tumor for each specific patient, and exploration of new therapies will be of great significance for the treatment of malignant digestive tumors. Digestive cancer is a highly heterogeneous disease in which each cancer patient exhibits a distinct genetic, epigenetic, and molecular profile. Unfortunately, although numerous studies have been conducted on molecular biomarkers, most of the identified biomarkers have failed in validation studies. Novel biomarkers are urgently needed for the early detection of GI cancers.

This Special Issue aims to collect research into novel molecular biomarkers that are potentially promising for clinical practice as non-invasive biomarkers for early detection and prognosis of digestive cancer. We welcome both original research and review articles.

Potential topics include but are not limited to the following:

• Epigenetic alterations such as GSTP1, p15, p16, FAT4, CDH1, or CHFR
• Metastasis related-genes, including FGFR2, E-cadherin, PI3K/Akt/mTOR, MET, HER2, VEGF, or TP53
• Non-coding RNA, such as miRNAs, tsRNAs, and lncRNAs
• Immune checkpoints including PD-1/2, PD-L1/2, TIM3
• Comprehensive gene analysis
• Microsatellite instability
• Genetic polymorphisms such as IL-1 or CD44
• Circulating tumor cells
• Advances in applied conventional biomarkers, for example, serum tumor markers, such as CEA, CA19-9, and CA72-4
• Molecular signatures for GI cancer diagnosis and prognosis
• Other potential biomarkers