Myopenia and Mechanisms of Chemotherapy Toxicity in Older Adults With Colorectal Cancer

Inclusion Criteria:

• Newly diagnosed metastatic CRC or newly recognized metastatic recurrence of CRC >=to 3 months (12 weeks) from completion of treatment of non-metastatic CRC.

• Planning to or recently started to undergo undergo immunotherapy and/or 5-FU basedchemotherapy as a first line of treatment. 5-FU chemotherapy can be 5-FU alone or incombination with oxaliplatin and/or irinotecan +/- immunotherapy. Capecitabine isalso acceptable.

• Estimated life expectancy >= 6 months.

• Patients must be able to comprehend English or Spanish (for questionnairecompletion).

• Ability to understand and the willingness to sign a written informed consentdocument.

• Patient eligibility is not dependent on BMI or weight. Patients with a significant (+- > 10%) body weight change in the previous 12 months are eligible for this study.

Exclusion Criteria:

• Patients enrolled on hospice.

• Prior systemic chemotherapy for metastatic colorectal cancer (ok if adjuvantchemotherapy completed >= 3 months (12 weeks) prior to this disease diseaserecurrence and treatment).

• Patients may not be receiving any other investigational agents.

• No untreated brain metastases. Patients with treated brain metastases are eligible.

• Patients on or planned to undergo radiation therapy in near future.