Inclusion Criteria:  Adult individuals (>18 years of age) Having signed the consent form Willingness to collaborate  Able to provide a breath sample  For the cancer group: colorectal adenocarcinoma has to be documented histologically (histological diagnosis following gastric surgery is also accepted) or patients being confirmed adenocarcinoma during the course of the study. For the non-cancer group: control group - any patient who have medical indications for a colonoscopy  Exclusion Criteria:  The patient has not signed the consent form Patients who have had a complete bowel cleansing Other active malignancies Neoadjuvant chemotherapy, radiation therapy is currently underway Acute conditions (emergency surgery for the patient) Small bowel resection in the past Terminal renal failure (Chronic renal failure stage 4) Type I diabetes Bronchial asthma (active)