This is a a prospective observational single-center study; it is a spontaneous study, not sponsored by pharmaceutical companies, and does not involve the use of experimental drugs. The study involves a collection of data, carried out while protecting the anonymity and personal information of individual patients suffering from neoplasms of the gastrointestinal tract, the execution of peripheral blood samples and the collection of faecal material at pre-determined times -points. Circulating biomarkers (as ctDNA) will be evaluated in these samples, in order to optimize both the diagnostic and therapeutic processes of patients with tumors of the gastrointestinal tract.