Patients receive irinotecan IV over 30 minutes on days 1, 8, and 15 and cisplatin IV over 60 minutes on day 1. Treatment repeats every 28 days for 4 courses in the absence of disease progression or unacceptable toxicity. Patients also receive oral imatinib mesylate once or twice daily beginning on day 22 of course 1 and continuing until disease progression or unacceptable toxicity.