Circulating Tumor Cells in Patients With Locally Advanced Rectal Cancer

PRIMARY OBJECTIVES: I. To establish the rate of circulating tumor elements (CTE), including but not limited to circulating tumor cells and circulating tumor deoxyribonucleic acid (DNA) detection in patients with locally advanced rectal cancer (LARC), relative to other stages. II. To assess changes in detected CTEs associated with neoadjuvant therapy in patients with LARC. III. To correlate CTEs with neoadjuvant treatment response as an indicator of disease risk. OUTLINE: Patients and healthy participants undergo collection of blood sample at baseline. Patients may also undergo collection of blood sample collections during tumor surgery, 4 weeks after surgery or after completion of treatment if you are not surgery, 8 weeks after the last dose of chemotherapy, 1 year after surgery or 1 year after completion of treatment if not having surgery, 2 years after surgery or 2 years after completion of treatment if not having surgery, and within 6 years after treatment or at the end of the 6 year follow-up if the disease gets worse with treatment or comes back.