OUTLINE: Patients are stratified according to prior response duration (progression 90 days or more after initial therapy vs progression less than 90 days after initial therapy or no response to initial therapy). Patients receive gemcitabine IV over 30 minutes and irinotecan IV over 90 minutes on days 1 and 8. Treatment continues every 21 days in the absence of disease progression or unacceptable toxicity. Patients are followed every 3 months for 1 year, then every 6 months for 2 years, and then annually for 3 years.