Testing the Addition of an Anti-Cancer Drug, Irinotecan, to the Standard Chemotherapy Treatment (FOLFOX) After Long-Course Radiation Therapy for Advanced-Stage Rectal Cancers to Improve the Rate of Complete Response and Long-Term Rates of Organ Preservation

This phase II trial compares the effect of irinotecan versus oxaliplatin after long-course chemoradiation in patients with stage II-III rectal cancer. Combination chemotherapy drugs, such as FOLFIRINOX (fluorouracil, irinotecan, leucovorin, and oxaliplatin), FOLFOX (leucovorin, fluorouracil, oxaliplatin, and irinotecan ), and CAPOX (capecitabin and oxaliplatin) work in different ways to stop the growth of tumor cells, either by killing the cells, by stopping them from dividing, or by stopping them from spreading. FOLFOX or CAPOX are used after chemoradiation as usual treatment for rectal cancer. Giving FOLFIRINOX after chemoradiation may increase the response rate and lead to higher rates of clinical complete response (with a chance of avoiding surgery) compared to FOLFOX or CAPOX after chemoradiation in patients with locally advanced rectal cancer.

Inclusion Criteria:Stage: Clinical stage II or III rectal adenocarcinoma defined as T4N0 or any T with node positive disease (any T, N+); also T3N0 requiring abdominal perineal resection (APR) or coloanal anastomosisTumor site: Rectum; =< 12cm from the anal vergeNo prior systemic chemotherapy, targeted therapy, or immunotherapy; or radiation therapy administered as treatment for colorectal cancer within the past 5 years is allowedNot pregnant and not nursing, because this study involves an agent that has known genotoxic, mutagenic and teratogenic effects* Therefore, for women of childbearing potential only, a negative pregnancy test (urine or serum according to institutional guidelines) done =< 14 days prior to registration is required. Female subjects agree to use highly effective contraception combined with an additional barrier method (e.g, diaphragm, with a spermicide) while on study and for >= 9 months after last dose of study drug, and the same criteria are applicable to male subjects if they have a partner of childbirth potential. Male subject agrees to use a condom and not donate sperm while in this study and for >= 6 months after the last treatmentAge >= 18 yearsEastern Cooperative Oncology Group (ECOG) performance status =< 2 (or Karnofsky >= 60%)Absolute neutrophil count (ANC) >= 1,500/mm^3Platelet count >= 100,000/mmCreatinine =< 1.5 x upper limit of normal (ULN) OR calculated (calc.) creatinine clearance >= 50 mL/min^3Total bilirubin =< 1.5 x upper limit of normal (ULN)Aspartate aminotransferase (AST)/alanine aminotransferase (ALT) =< 3 x upper limit of normal (ULN)No upper rectal tumors (distal margin of tumor > 12 cm from the anal verge)No recurrent rectal cancer; prior transanal excision, prior distal sigmoid cancer with a low anastomosisNo known mismatch repair deficient rectal adenocarcinomaHuman immunodeficiency virus HIV-infected patients on effective anti-retro viral therapy with undetectable viral load within 6 months are eligible for this trialPatients with known history or current symptoms of cardiac disease, or history of treatment with cardio toxic agents, should have a clinical risk assessment of cardiac function using the New York Heart Association Functional Classification1. To be eligible for this trial, patients should be class 2B or betterChronic concomitant treatment with strong inhibitors of CYP3A4 is not allowed on this study. Patients on strong CYP3A4 inhibitors must discontinue the drug for 14 days prior to registration on the study * Chronic concomitant treatment with strong CYP3A4 inducers is not allowed. Patients must discontinue the drug 14 days prior to the start of study treatment