Patients receive oral celecoxib twice daily on days -7 to 21 during course 1 and on days 1-21 in all subsequent courses. Patients also receive oral capecitabine twice daily on days 1-14 and irinotecan IV over 30 minutes on days 1 and 8. Courses repeat every 21 days in the absence of disease progression or unacceptable toxicity. Patients achieving a complete or partial response after 4 courses may temporarily discontinue treatment for no more than 4 weeks.