Adding Pertuzumab to Trastuzumab/Capecitabine in Pretreated HER2-Positive Metastatic Breast Cancer
The phase III PHEREXA trial has shown no significant improvement in progression-free survival with the addition of pertuzumab (Perjeta) to trastuzumab (Herceptin)/capecitabine in patients with HER2-positive metastatic breast cancer with disease progression during or after trastuzumab-based treatment who had received prior taxane therapy. These study findings were reported by Urruticoechea et al in the Journal of Clinical Oncology. Overall survival was longer in the pertuzumab group, although statistical significance could not be claimed for the difference.
Study Details
In the open-label trial, 452 patients from 171 sites in 22 countries were randomized between January 2010 and August 2013 to receive trastuzumab (8 mg/kg and then at 6 mg/kg once every 3 weeks) plus capecitabine (1,250 mg/m2 twice daily for 2 weeks on/1 week off every 3 weeks; n = 224) or pertuzumab (840 mg and then 420 mg once every 3 weeks) plus trastuzumab (same dose and schedule) and capecitabine (1,000 mg/m2; same schedule; n = 228). The primary endpoint was independent review facility–assessed progression-free survival. A hierarchical testing procedure was used whereby testing for statistical significance of overall survival would be performed only if the difference between groups in progression-free survival were significant.
Progression-Free and Overall Survival
At median follow-up of 25.3 months in the pertuzumab group and 28.6 months in the control group, median progression-free survival was 11.1 months vs 9.0 months (hazard ratio [HR] = 0.82, P = .0731). At preplanned interim analysis, median overall survival was 36.1 months vs 28.1 months (HR = 0.68, 95% confidence interval = 0.51–0.90).
Adverse Events
The most common adverse events of any grade with an incidence of ≥ 10% in either group and a ≥ 5% difference between groups were diarrhea (70% vs 59%), rash (15% vs 5%), and nasopharyngitis (11% vs 6%) in the pertuzumab group and hand-foot syndrome (73% vs 56%), nausea (45% vs 39%), and neutropenia (18% vs 13%) in the control group.
The investigators concluded: “The addition of pertuzumab to trastuzumab and capecitabine did not significantly improve [independent review facility–assessed progression-free survival]. An 8-month increase in median [overall survival] to 36.1 months with pertuzumab was observed. Statistical significance for [overall survival] cannot be claimed because of the hierarchical testing… after the primary [progression-free survival] end point; however, the magnitude of [overall survival] difference is in keeping with prior experience of pertuzumab in metastatic breast cancer. No new safety signals were identified.”
The study was supported by F. Hoffmann-La Roche.
Ander Urruticoechea, MD, of Onkologikoa Foundation, San Sebastián, Spain, is the corresponding author of the Journal of Clinical Oncology article.
The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.
