Trametinib, Fluorouracil, and Radiation Therapy Before Surgery in Treating Patients With Stage II-III Rectal Cancer

PRIMARY OBJECTIVES: I. To identify the maximally tolerated dose and recommended phase II dose of trametinib to be used in combination with 5FU (fluorouracil) and radiation in patients with rectal cancers. II. To determine a recommended phase II dose of trametinib to be used with 5FU chemoradiation in patients with locally advanced rectal cancer. SECONDARY OBJECTIVES: I. Evaluation of the tolerability and safety of the combination of trametinib and 5-FU chemoradiation in locally advanced rectal cancer. II. Evaluation of post-therapy pathologic response. III. Evaluation of the rate of local control, disease-free survival and overall survival. IV. Analysis of biomarkers - total mutations in v-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog (KRAS), v-raf murine sarcoma viral oncogene homolog B1(BRAF), and neuroblastoma RAS viral (v-ras) oncogene homolog (NRAS), as well as RAS/mitogen-activated protein kinase (MAPK) and phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K)/v-akt murine thymoma viral oncogene homolog 1 (AKT) pathway signaling pathways to potentially correlate with clinical benefit. OUTLINE: This is a dose-escalation study of trametinib. Patients receive trametinib orally (PO) once daily (QD) on days -14 to -10 and 1-38 and fluorouracil intravenously (IV) continuously 5 days a week from days 1-38. Patients also undergo radiation therapy 5 days a week on days 1-33. Patients then undergo surgery 6-10 weeks later. Patients achieving negative surgical margins after complete resection of tumor receive postoperative chemotherapy comprising leucovorin calcium IV over 2 hours and fluorouracil IV continuously over 46 hours on days 1 and 15 OR oxaliplatin IV over 2 hours, leucovorin calcium IV over 2 hours and fluorouracil IV continuously over 46 hours on days 1 and 15. Treatment repeats every 28 days for up to 4 courses in the absence of disease progression or unacceptable toxicity. After completion of study treatment, patients are followed up every 3 months for 2 years, and then annually for 3 years.