Patients receive alisertib orally (PO) twice daily (BID) on days 1-3 and mFOLFOX regimen comprising oxaliplatin intravenously (IV) over 2 hours on day 2, leucovorin calcium IV over 2 hours on day 2, and fluorouracil IV continuously over 46 hours on days 2-4. Courses repeat every 14 days in the absence of disease progression or unacceptable toxicity.