Background
Phase III, double-blind, placebo-controlled RCT. 808 patients with HER2+ locally recurrent or metastatic breast cancer with no prior treatment for metastatic disease and no prior pertuzumab. Dual HER2 blockade (pertuzumab + trastuzumab) combined with docetaxel vs trastuzumab + docetaxel + placebo. Pertuzumab and trastuzumab bind complementary epitopes on HER2, providing non-overlapping mechanisms of blockade.
Interventions and follow up
Arm A: Pertuzumab 420mg q3wk (loading 840mg) + trastuzumab 6mg/kg q3wk + docetaxel 75mg/m² q3wk
Arm B: Placebo + trastuzumab + docetaxel
Primary endpoint: Progression-free survival (PFS)
mFollow up: 50 months (OS analysis)
Arm B: Placebo + trastuzumab + docetaxel
Primary endpoint: Progression-free survival (PFS)
mFollow up: 50 months (OS analysis)
Results
PFS: 18.7 vs 12.4mo, HR 0.68, 95% CI 0.58–0.80, P<.001
OS (final): 57.1 vs 40.8mo, HR 0.69, 95% CI 0.58–0.82, P<.001
OS (final): 57.1 vs 40.8mo, HR 0.69, 95% CI 0.58–0.82, P<.001
Adverse events
Gastrointestinal: Grade ≥3 diarrhea 7.9% vs 5.0%
Hematologic: Grade ≥3 febrile neutropenia 13.8% vs 7.6%
Cardiac: Grade ≥3 left ventricular dysfunction 1.0% vs 1.2% (similar) — pertuzumab adds minimal cardiac toxicity to trastuzumab
Neurologic: Peripheral neuropathy grade ≥3 1.2%
Hematologic: Grade ≥3 febrile neutropenia 13.8% vs 7.6%
Cardiac: Grade ≥3 left ventricular dysfunction 1.0% vs 1.2% (similar) — pertuzumab adds minimal cardiac toxicity to trastuzumab
Neurologic: Peripheral neuropathy grade ≥3 1.2%
Conclusions
Pertuzumab + trastuzumab + docetaxel (THP) significantly improved both PFS (6-month gain) and OS (~16-month gain) vs trastuzumab + docetaxel in first-line HER2+ mBC. The OS benefit of ~16 months is among the largest demonstrated in an mBC trial and established dual HER2 blockade as the standard of care.
Key Limitations
Key Limitations: Chemotherapy backbone was docetaxel only — many current regimens substitute paclitaxel or use taxane + carboplatin (TCHP) to reduce neutropenic complications. Duration of chemotherapy before transitioning to pertuzumab + trastuzumab maintenance was not standardized in CLEOPATRA; current practice typically limits docetaxel to 6–8 cycles. DESTINY-Breast09 (2025) directly compared T-DXd to CLEOPATRA-style THP in first-line HER2+ mBC, potentially superseding THP as first-line standard.
Clinical Context
CLEOPATRA established pertuzumab + trastuzumab + taxane (THP) as the global standard of care for first-line HER2+ mBC (FDA approved 2012 for neoadjuvant; extended to metastatic 2013). ESMO-MCBS score: 5. The 57-month median OS transformed HER2+ mBC prognosis. With T-DXd emerging as a superior second-line option (DB03) and potentially first-line (DB09), CLEOPATRA's positioning continues to evolve.
References