As reported in The Lancet Oncology by Sandra M. Swain, MD, and colleagues, long-term follow-up of the phase III CLEOPATRA trial has shown maintained overall survival benefit with the addition of pertuzumab to trastuzumab plus docetaxel in patients with previously untreated HER2-positive metastatic breast cancer.
"HER2-targeted therapy has changed the natural history of HER2-positive metastatic breast cancer, with the dual blockade of pertuzumab and trastuzumab, with docetaxel, demonstrating an 8-year landmark overall survival rate of 37%.”— Sandra M. Swain, MD, and colleagues
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In the international double-blind trial, 808 patients were randomly assigned between February 2008 and July 2010 to receive docetaxel and trastuzumab plus pertuzumab (n = 402) or docetaxel and trastuzumab plus placebo (n = 406). The primary analysis and subsequent reports from the trial showed significantly improved progression-free survival and overall survival in the pertuzumab vs placebo group. In the current end-of-study analysis, 50 patients who crossed over from the placebo group to the pertuzumab group during the trial are included as part of the placebo group.
Median follow-up was 99.9 months in the pertuzumab group and 98.7 months in the placebo group.
On intent-to-treat analysis, median overall survival was 57.1 months in the pertuzumab group vs 40.8 months in the placebo group (hazard ratio [HR] = 0.69, 95% confidence interval [CI] = 0.58–0.82). Landmark overall survival rates were 49% vs 35% at 5 years, 45% vs 28% at 6 years, 40% vs 26% at 7 years, and 37% vs 23% at 8 years. Median investigator-assessed progression-free survival was 18.7 vs 12.4 months (HR = 0.69, 95% CI = 0.59–0.81).
Overall, the most commonly reported grade 3 or 4 adverse event was neutropenia, observed in 49% vs 46% of patients. Treatment-related death occurred in five (1%) patients in the pertuzumab group vs six (2%) patients in the placebo group. Since the most recent analysis, one new serious adverse event—suggestive of congestive heart failure—occurred in a patient in the pertuzumab group, and new symptomatic left ventricular systolic dysfunction occurred in one patient who had crossed over from the placebo to the pertuzumab group.
The investigators concluded, “Our analysis shows that the previously observed improvements in overall survival with pertuzumab, trastuzumab, and docetaxel vs placebo, trastuzumab, and docetaxel were maintained after a median of more than 8 years of follow-up. The long-term safety and cardiac safety profiles of pertuzumab, trastuzumab, and docetaxel were maintained…HER2-targeted therapy has changed the natural history of HER2-positive metastatic breast cancer, with the dual blockade of pertuzumab and trastuzumab, with docetaxel, demonstrating an 8-year landmark overall survival rate of 37%.”
Dr. Swain, of Georgetown University Medical Center, is the corresponding author for The Lancet Oncology article.
Disclosure: The study was funded by F. Hoffmann-La Roche and Genentech. For full disclosures of the study authors, visit thelancet.com.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®.