The Impact of Initial Tumor Response on Survival Outcomes of Patients With HER2-Positive Advanced Breast Cancer Treated With Docetaxel, Trastuzumab, and Pertuzumab: An Exploratory Analysis of the CLEOPATRA Trial.

Introduction: The CLEOPATRA trial (NCT00567190) established a dual anti-HER2 blockade in combination with docetaxel as the first-line standard of care for patients with metastatic HER2-positive breast cancer. While this treatment is overall associated with significant improvement in progression-free survival (PFS) and overall survival (OS), not all patients respond equally. We hypothesized that a radiological complete response (CR) at week 9 (i.e., first disease re-evaluation) is associated with prolonged OS and PFS compared to radiological partial response (PR) or stable disease (SD).
Methods: We performed an exploratory analysis of the CLEOPATRA study to address this question.
Results: Out of 362 patients treated with docetaxel, trastuzumab, and pertuzumab eligible for our analysis, 46 (12.7%) had radiological CR at week 9, 243 (67.1%) PR, and 73 (20.2%) SD per central RECIST v1.0. Radiological CR at first tumor re-evaluation was associated with a 60% risk reduction for death compared to SD (adjusted HR = 0.40 95% confidence interval (CI) 0.23-0.70), whereas no significant impact on survival was observed for PR (adjusted HR = 0.85 95% CI 0.60-1.20). The same was observed for PFS with adjusted HR = 0.30 (95% CI 0.18-0.48) for the CR subgroup and adjusted HR = 0.81 (95% CI 0.60-1.09) for the PR subgroup. In multivariate analysis, no variables were associated with radiological CR.
Conclusions: Our findings suggest that radiological CR at first disease re-evaluation is associated with more prolonged survival; this might result from stronger dependence on HER2 pathway addiction, supporting the need for further translational research.
Competing Interests: Disclosure VD, MB, MC, FJ: none; EA: consultancy fee/honoraria from Eli Lilly, Sandoz, AstraZeneca. Research grant to my Institution from Gilead; Support to attend medical conferences (travel/accommodation/expenses) from Novartis, Roche, Eli Lilly, Genetic, IstitutoGentili, Daiichi Sankyo (all outside the submitted work); CM: honoraria from Novartis and Lilly; DMB: declares full-time employment from the European Society for Medical Oncology since September 1, 2023; speaker's engagement from AstraZeneca, Daiichi Sankyo; meeting/travel grant from Novartis; institutional research funding from Eli Lilly, F. Hoffmann-La Roche Ltd, Novartis; non-remunerated activity as a member of the board of directors for Associaҫão de Investigaҫão e Cuidados de Suporte em Oncologia; non-remunerated leadership role as prior Portuguese Young Oncologists; Committee Chair of Sociedade Portuguesa de Oncologia; GNM: support to attend medical conferences: Roche and Bayer (all outside the submitted work); ML: honoraria and/or advisory board from Roche, Novartis, Lilly, Pfizer, AstraZeneca, Daiichi Sankyo, Gilead, Seagen, MSD, Exact Sciences, Takeda, Ipsen, Sandoz, Libbsand Knight, a travel grant from Gilead and research support (to the Institution) from Gilead (all outside the submitted work); EdA: honoraria and/or advisory board from Roche/GNE, Novartis, Seattle Genetics, Zodiac, Libbsand Pierre Fabre. Travel grants from Roche/GNE and GSK/Novartis. Research grant to his institution from Roche/GNE, Astra-Zeneca, GSK/Novartis, and Servier(all outside the submitted work).
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