UCBG 2-04: Long-term results of the PACS 04 trial evaluating adjuvant epirubicin plus docetaxel in node-positive breast cancer and trastuzumab in the human epidermal growth factor receptor 2-positive subgroup

Abstract

Purpose: We conducted a double-randomised phase III trial to evaluate a concomitant taxane-anthracycline regimen in node-positive breast cancer and the efficacy of trastuzumab in the human epidermal growth factor receptor 2 (HER2)-positive subpopulation.

Methods: A total of 3010 patients with node-positive breast cancer were randomly assigned to receive 6 cycles of 500 mg/m² of fluorouracil, 100 mg/m² of epirubicin and 500 mg/m² of cyclophosphamide (FEC) or 75 mg/m² of epirubicin and 75 mg/m² of docetaxel (ED). Patients with HER2-positive tumours were secondary randomly assigned to either trastuzumab or observation. The primary end-point was disease-free survival (DFS) in the two chemotherapy arms.

Results: After a 115-month median follow-up, DFS was not significantly better in the ED arm (DFS: 70%, 95% confidence interval [CI]: 67-72) than in the FEC arm (DFS: 68%, 95% CI: 65-70; hazard ratio [HR] = 0.88, 95% CI: 0.77-1.01; p = 0.064). The OS was not different between FEC (OS: 80%, 95% CI: 78-83) and ED (OS: 81%, 95% CI: 79-83); HR = 0.97, 95% CI: 0.81-1.16; p = 0.729). ED appeared more toxic. In the 528 HER2-positive subset, there was trend for a higher DFS, in the intention-to-treat population, in the trastuzumab arm (DFS: 68%, 95% CI: 61-74) than in the observation arm (DFS: 60%, 95% CI: 54-66; HR = 0.77, 95% CI: 0.57-1.03; p = 0.079). In the per-protocol population, DFS was significantly higher in the trastuzumab arm (DFS: 70%, 95% CI: 63-76) than in the observation arm (DFS: 59%, 95% CI: 53-65; HR = 0.69, 95% CI: 0.51-0.94; p = 0.0156). The OS was not different between these 2 arms.

Conclusion: This study did not show superiority of the concomitant anthracycline-taxane arm which was more toxic in high-risk node-positive breast cancer patients. Long-term results of the HER2-positive subpopulation are in line with those of the other adjuvant trastuzumab trials but quantitatively less pronounced mostly because of lack of power.

Keywords: Adjuvant chemotherapy; Adjuvant trastuzumab; Breast cancer; Taxanes.