This trial studies the monitoring of therapy and progression by collecting blood, urine, and stool from participants with colorectal cancer that has spread to other places in the body or cannot be removed by surgery. Studying samples of blood, urine, and stool from participants with colorectal cancer in the laboratory may help doctors identify and learn more about biomarkers related to cancer.

PRIMARY OBJECTIVES:

I. Detection of mutated Kras in urine specimen of patients with Kras mutated metastatic colon cancer on first, second, or third line therapy.

II. Detection of new Kras in urine in patients without Kras mutated metastatic colon cancer on therapy which includes anti-EGFR antibodies (cetuximab or panitumumab).

SECONDARY OBJECTIVES:

I. Changes of the stool microbiome with chemotherapy and at progression of the disease.

DESCRIPTIVE OBJECTIVES:

I. Changes in the quantity of mutated Kras, Braf or PI3K in urine deoxyribonucleic acid (DNA) over the cycles of first line therapy.

II. Associations between the quantity of mutated Kras, Braf or PI3K in urine DNA, molecular make up of circulating tumor cells (CTCs), cell free DNA and progression over the course of first line therapy.

III. Feasibility of detection of exosome in the plasma of colorectal cancer patients on first line chemotherapy in Dr. Fabbri?s lab at Children?s Hospital Los Angeles.

IV. Feasibility of detection of tumor DNA in the plasma of colorectal cancer patients on first line chemotherapy.

OUTLINE:

Participants undergo collection of blood and urine at baseline, on day 1 of courses 1, 2, and 3, at restaging, and at disease progression. Participants may undergo collection of stool at baseline, on day 1 of course 2, and at disease progression. Participants also undergo biopsy within 4 weeks of disease progression.

Inclusion Criteria:

• All patients with metastatic/unresectable colorectal cancer who will undergo first, second, or third line therapy; the participating investigator will select treatment, however, patients with Kras wild type must receive anti-EGFR therapy to be eligible for this study
• Subject consent to enrollment on the protocol
• Histologically confirmed metastatic or un-resectable colorectal cancer, known Kras status; knowledge of other mutations is optional
• Willingness to undergo biopsy at the time of progression
• Willingness to follow the study instructions for collection of specimens
• Available archival tissue

Participants with metastatic/unresectable colorectal cancer who will undergo first, second, or third line therapy at USC facilities will be recruited for this study.