Evaluating a Nonessential Amino Acid Restriction (NEAAR) Medical Food With Total Neoadjuvant Therapy for Locally Advanced Rectal Cancer (LARC)

Inclusion Criteria: * Histologically confirmed diagnosis of adenocarcinoma of the rectum * Clinical stage II (cT3-4, N-) or Stage III (cT any, N+) based on MRI * Eligible for total mesorectal excision * No evidence of distant metastasis * No prior pelvic radiation therapy * No prior chemotherapy * Age ≥18 years Exclusion Criteria: * Patients unable to undergo MRI * Other anticancer or experimental therapy * Body mass index (BMI) \<18.5 kg/m2 or \>40 kg/m2 * Serious or refractive cachexia or anorexia * Insulin-dependent diabetes Taking or needs to take any protein or amino acid containing nutritional supplements (e.g., Ensure®) Patients with a condition where high-fat or fatty food is contraindicated History of confirmed food allergy Active wound or skin graft that would require a significant increase in protein requirements for skin integrity and healing