Based on the data for irinotecan, it is estimated that the median PFS in the second-line chemotherapy arm will be 4 months. In order to demonstrate an improvement in median PFS to 5.5 months (37.5% improvement, hazard ratio of 0.73) based on a two-sided log rang test, 338 patients (169 per arm) will be required, assuming an 18 month enrollment and a 12 month follow-up, an alpha of 0.05 and 90% power. The sample size assumes a 10% loss to follow-up rate.