Randomized open label phase III trial of irinotecan plus capecitabine versus capecitabine monotherapy in patients with metastatic breast cancer previously treated with anthracycline and taxane: Proceed trial (KCSG BR 11-01)

Purpose We investigated whether irinotecan plus capecitabine improved progression-free survival (PFS) compared with capecitabine alone in patients with human epidermal growth factor 2 (HER2) negative and anthracycline and taxane pretreated metastatic breast cancer (MBC). Materials and Methods A total of 221 patients were randomly assigned to irinotecan (80 mg/m ² , days 1 and 8) and capecitabine (1,000 mg/m ² twice a day, days 1-14) or capecitabine alone (1,250 mg/m ² twice a day, days 1-14) every 3 weeks. The primary endpoint was PFS. Results There was no significant difference in PFS between the combination and monotherapy arm (median, 6.4 months vs. 4.7 months; hazard ratio [HR], 0.84; 95% confidence interval [CI], 0.63 to 1.11; p=0.84). In patients with triple-negative breast cancer (TNBC, n=90), the combination significantly improved PFS (median, 4.7 months vs. 2.5 months; HR, 0.58; 95% CI, 0.37 to 0.91; p=0.02). Objective response rate was numerically higher in the combination arm, though it failed to reach statistical significance (44.4% vs. 33.3%, p=0.30). Overall survival did not differ between arms (median, 20.4 months vs. 24.0 months; p=0.63). While grade 3 or 4 neutropenia was more common in the combination arm (39.6% vs. 9.0%), hand-foot syndrome was more often observed in capecitabine arm. Quality of life measurements in global health status was similar. However, patients in the combination arm showed significantly worse symptom scales especially in nausea/vomiting and diarrhea. Conclusion Irinotecan plus capecitabine did not prove clinically superior to single-agent capecitabine in anthracycline- and taxane-pretreated HER2 negative MBC patients. Toxicity profiles of the two groups differed but were manageable. The role of added irinotecan in patients with TNBC remains to be elucidated.