The purpose of this study is to find out how cancer treatments (chemotherapy and/or radiation therapy) affect reproductive and sexual health in people with early onset colorectal cancer. The study researchers will observe and track changes in hormone levels and in sexual and reproductive health in people with early onset colorectal cancer. This information will help researchers know more about how cancer treatments affect reproductive and sexual health, including the ability to have children (fertility).

Inclusion Criteria:

• 18-40 years of age and premenopausal (female) or 18-50 years of age (male) at time of diagnosis
• Histologic diagnosis of colorectal adenocarcinoma
• Able and willing to participate in the informed consent process
• Eligible for curative adjuvant or neoadjuvant therapy for colon or rectal cancer
• Willing and able to complete protocol questionnaires
• Rectal patients only: Individuals who will be receiving chemotherapy, followed by chemoradiotherapy (ChemoRT)

Exclusion Criteria:

• Prior systemic treatment for this malignancy
• Active or prior secondary malignancy
• History of ovarian resection (if female)
• Pregnant or nursing (lactating) women, where pregnancy is defined as the state of a female after conception until the termination of gestation, confirmed by a positive hCG laboratory test.

Potential research subjects will be identified through the Center for Young Onset Colorectal 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.