The purpose of this registry study is to create a database-a collection of information-for better understanding young onset colorectal cancer. Colorectal cancer patients are considered to have young onset colorectal cancer if they are diagnosed with their cancer before the age of 50. Researchers will use the information from this database to learn more about how young onset colorectal cancer may be similar to or different from colorectal cancer that is diagnosed later in life. Researchers will also use information from the database for current and future research on young onset colorectal cancer.

Inclusion Criteria:

Participant Inclusion Criteria for database and questionnaire (YOGI)

• Histological or cytological diagnosis of gastrointestinal cancer
• 18 - 49 years old at time of consent
• No Known hereditary CRC or other cancer predisposition syndrome (stool collection cohort only)
• No history of inflammatory bowel disease (stool collection cohort only)
• No prior diagnosis of gastrointestinal cancer (stool collection cohort only)

Participant Inclusion Criteria for database and questionnaire (Controls)

• Histological or cytological diagnosis of colorectal adenocarcinoma
• No previous treatment for CRC (including surgery, chemotherapy, immunotherapy or radiation)
• Age 50 or older at time of consent
• No Known hereditary CRC or other cancer predisposition syndrome
• No history of inflammatory bowel disease
• No prior diagnosis of CRC

Potential research subjects will be identified through the Center for Young Onset Gastrointestinal Cancer, a member of the patient's treatment team, the principal investigator, or research team at Memorial Sloan Kettering Cancer Center (MSKCC). All study participants will be recruited from patients under the care of consenting professionals. If the investigator is a member of the treatment team, s/he will screen their patient's medical records for suitable research study participants and discuss the study and their potential for enrolling in the research study. Potential subjects contacted by their treating physician will be referred to the investigator/research staff of the study.

Memorial Sloan Kettering Cancer Center supports the international committee of medical journal editors (ICMJE) and the ethical obligation of responsible sharing of data from clinical trials. The protocol summary, a statistical summary, and informed consent form will be made available on clinicaltrials.gov when required as a condition of Federal awards, other agreements supporting the research and/or as otherwise required. Requests for deidentified individual participant data can be made beginning 12 months after publication and for up to 36 months post publication. Deidentified individual participant data reported in the manuscript will be shared under the terms of a Data Use Agreement and may only be used for approved proposals. Requests may be made to: crdatashare@mskcc.org.