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43rd Annual Miami Breast Cancer Conference® - Abstracts

75 Trastuzumab Deruxtecan in HER2-Low Metastatic Breast Cancer: Real-World Treatment Patterns and Outcomes From Community Oncology Settings

ByMarvin Nguyen,Ruchit Shah,Anagha Gogate,Deepak Adhikari,Lisa Herms,Heather Neuhalfen,Aaron Peevyhouse,Scott Cole,Sibel Blau,Mark Walker

T-DXd demonstrated a real-world overall response rate of 56.3%, median rwPFS of 7.4 months, and 12-month OS of 62% in patients with HER2-low metastatic breast cancer treated across US community oncology settings.

76 Real-World Safety of Trastuzumab Deruxtecan in HER2-Low Metastatic Breast Cancer: Insights From US Community Oncology Practices

ByMark Walker,Marvin Nguyen,Ruchit Shah,Anagha Gogate,Deepak Adhikari,Lisa Herms,Heather Neuhalfen,Aaron Peevyhouse,Scott Cole,Sibel Blau

In a real-world cohort of 300 patients with HER2-low metastatic breast cancer, T-DXd demonstrated a safety profile consistent with DESTINY-Breast04 in community oncology settings, with ILD/pneumonitis in 10% and toxicity-related discontinuation in 15%.

77 Updated Efficacy of Mutant-Selective PI3Kα Inhibitor Zovegalisib (RLY-2608) in Combination With Fulvestrant in Patients With PIK3CA-Mutant HR+/HER2– Advanced Breast Cancer: ReDiscover Trial

BySarah L. Sammons,Cristina Saura,Antoine Italiano,Alison Schram, MD,Pablo Tolosa,Anne F. Schott, MD,Á. Guerrero-Zotano,Santiago Ponce-Aix,Rita Nanda, MD,Kari B. Wisinski, MD,Jennifer Segar,Mei Wei,Jia (Jenny) Liu,Alexander Spira, MD, PhD, FACP, FASCO,Julia E. McGuinness, MD,Jordi Rodón,Cynthia X. Ma, MD, PhD,Milana Bergamino,Giuseppe Curigliano,Andreas Varkaris

Zovegalisib plus fulvestrant demonstrated an objective response rate of 38.7% and a median progression-free survival of 10.3 months in PIK3CA-mutant HR+/HER2– advanced breast cancer in the ReDiscover trial.

78 Liquid Biopsy Insights: Genomic Drivers of Endocrine Resistance in Breast Cancer

ByHeidi C. Ko,Ellen Verner,Laine V. Morris,Rebecca Previs, MD,Melissa Krystel-Whittemore,Kalpeshkumar Patel,Kyle C. Strickland,Shakti Ramkissoon,Marcela Mazo Canola,Pareshkumar Patel

ctDNA-based next-generation sequencing in 236 patients with advanced breast cancer revealed frequent PIK3CA, TP53, and ESR1 mutations, highlighting key mechanisms of endocrine resistance with implications for targeted therapy selection.

80 Datopotamab Deruxtecan (Dato-DXd) + Durvalumab (D) as First-Line (1L) Treatment (tx) for Unresectable Locally Advanced/Metastatic Triple-Negative Breast Cancer (a/mTNBC): Final Results From the Phase 1b/2 BEGONIA Study

ByPeter Schmid, MD,Hwei-Chung Wang,Filipa Lynce,Yeon Hee Park,Cynthia X. Ma, MD, PhD,Kyung Hae Jung,Shin-Cheh Chen,Ming-Feng Hou,Catherine Prady,Ling-Ming Tseng,Jamil Asselah,Piotr J. Wysocki,Simon Lord,Purnima Rao-Melacini,Ross Stewart,Karola Warzyszyńska,Petra Vuković,Seock-Ah Im

Dato-DXd plus durvalumab demonstrated robust antitumor activity as first-line treatment for advanced/metastatic triple-negative breast cancer in the phase 1b/2 BEGONIA study, with manageable safety.

81 A First-in-Human Study of a Selective ERBB2 Inhibitor, CGT4255, in Patients Who Have Advanced Solid Tumors With ERBB2 Genetic Alterations or HER2 Overexpression

ByDena Westphalen,Sarah Goldberg, MD, MPH ,Muhammad Rizwan Khawaja, MD, MPH,Jose Pacheco, MD,Jeffrey Russell,Joshua K. Sabari, MD,Jenna Zhang,Meredith Little,Kevin Moynihan,Kathleen Dorris,Mohamad Adham Salkeni

A phase 1/1b first-in-human study is evaluating the CNS-penetrant selective ERBB2 inhibitor CGT4255 across multiple tumor types, including HER2-positive breast cancer with brain metastases.

82 Facilitators and Barriers to Clinical Trial Participation in Metastatic Breast Cancer: Patient and Physician Perspectives to Advance Representation

ByDemetria Smith-Graziani,Shivani K Mhatre,Natalia Sadetsky,Cosmina Hogea,Tiffany Bratts,Chloe Hayes,Pooja Advani, MBBS, MD

A dual-perspective survey of patients and physicians with metastatic breast cancer identified financial, logistical, and trust-related barriers to trial participation, with greater burden among racial and ethnic minorities.

84 Exceptional Responders in De Novo Metastatic Breast Cancer (dnMBC) Drug Cessation in Patients With HER2-Positive Metastatic Breast Cancer; Multicenter Retrospective Study

ByMutlu Dogan,Berk Goktepe,Mehmet Bilici,Sercan Aksoy,Fatih Selcukbiricik,Ali Alkan,Arzu Oguz,Arzu Yasar,Naziye Ak,Betul Ersoz,Lutfi Dogan,Merve Tokocin,Yasemin Evlendi,Ozlem Soran,Qurat Ul Ain Sabih,Julia Foldi,Atilla Soran, MD, MPH

Extended drug cessation appears feasible in exceptional responders with HER2+ de novo metastatic breast cancer, with significantly better survival compared with non-exceptional responders.

86 Gedatolisib, a Multitarget PI3K/AKT/mTOR (PAM) Inhibitor, Plus Fulvestrant With or Without Palbociclib for Second-Line (2L) Treatment of Patients With HR+/HER2–/PIK3CA-Wild Type (WT) Advanced Breast Cancer (ABC): Updated Results From VIKTORIA-1

ByBarbara Pistilli,Rachel M. Layman,Giuseppe Curigliano,Massimo Cristofanilli, MD,Robert Wesolowski,Hyo S Han,Antonio Giordano,Igor Gorbatchevsky,Sara A. Hurvitz, MD

Gedatolisib combinations significantly extend progression-free survival after CDK4/6 inhibitor failure in HR+/HER2– breast cancer, with manageable adverse effects and stable quality of life.

88 Imlunestrant With or Without Abemaciclib in Advanced Breast Cancer (ABC): A Subgroup Analysis in CDK4/6 Inhibitor (CDK4/6i)-Pretreated Patients From EMBER-3

ByCristina Saura,Lisa A. Carey, MD,Giuseppe Curigliano,Nadia Harbeck, MD, PhD,Joyce O’Shaughnessy, MD,François-Clément Bidard,Monica Lis Casalnuovo,Sung-Bae Kim,Eriko Tokunaga,Norikazu Masuda,Junichiro Watanabe,Xiaojia Wang,Quchang Ouyang,Hee Kyung Ahn,Christoph Cramer von Laue,Shanshan Cao,Holly Knoderer,Komal L. Jhaveri,Philippe Aftimos

89 Imlunestrant With or Without Abemaciclib as First- and Second-Line Therapy in Advanced Breast Cancer (ABC): A Subgroup Analysis From the EMBER-3 Trial

ByPatrick Neven, MD, PhD,Andre Mattar,Antonio Llombart-Cussac,Giuseppe Curigliano,Nadia Harbeck, MD, PhD,Joyce O’Shaughnessy, MD,François-Clément Bidard,Monica Lis Casalnuovo,Sung-Bae Kim,Eriko Tokunaga,Cristina Saura,Lisa A. Carey, MD,Kamnesh R. Pradhan,Shanshan Cao,Monique Coersmeyer,Anna Emde,Francisco Sapunar,Komal L. Jhaveri,Philippe Aftimos

93 monarchE: Primary Overall Survival Results of Adjuvant Abemaciclib + Endocrine Therapy for HR+/HER2−, High-Risk, Early Breast Cancer

ByStephen R.D. Johnston,Miguel Martin, MD, PhD,Joyce O’Shaughnessy, MD,Roberto Hegg,Sara M. Tolaney, MD, MPH,Valentina Guarneri, MD,Lucia Del Mastro,Mario Campone,Javier Cortés, MD,Hope S. Rugo, MD,Matthew P. Goetz, MD,Erika P. Hamilton, MD,Elzbieta Senkus,Laura Testa,Patrick Neven, MD, PhD,Jens Huober, MD,Ran Wei,Maria Munoz,Priya Rastogi, MD,Nadia Harbeck, MD, PhD,Victoria Jennifer Stefaniak (Non-Author Presenter)

95 monarchE: Subgroup Analysis of Adjuvant Abemaciclib + Endocrine Therapy for HR+/HER2−, High-Risk, Early Breast Cancer by Nodal Status

ByJavier Cortés, MD,Stephen R.D. Johnston,Miguel Martin, MD, PhD,Sara M. Tolaney, MD, MPH,Matthew P. Goetz, MD,Hope S. Rugo, MD,Joohyuk Sohn,Ozgur Ozyilkan,Miguel Henriques Abreu,Matthias Zaiss,Karina Maia Vianna,Hanne Melgaard Nielsen,Arlene Chan,Haralambos Kalofonos, MD,Serafin Morales,Belen San Antonio,Maria Munoz Fernandez,Sasha Amdur,Patrick Neven, MD, PhD,Brenda Grimes

98 A Phase 1/2 Trial of LY4064809, A Pan-Mutant-Selective PI3Kα Inhibitor in HR+/HER2− Advanced Breast Cancer, Updated Results From PIKALO-1

ByKomal L. Jhaveri,Dejan Juric,Antonio Giordano,Antoine Italiano,Gennaro Daniele,Jordi Rodón,Amita Patnaik, MD,Jorge Bartolomé,Anthony D. Elias, MD,Pamela N. Munster, MD,Patricia Lorusso, DO,Aixa Soyano,Maria de Miguel,Joyce O’Shaughnessy, MD,Robert Wesolowski,Giuseppe Curigliano,Tatiana Hernández,Aurélie Lombard,Shawn T. Estrem,Lin Du,Xiaofan Xu,Alberto J. Montero, MD, MBA, CPHQ

99 Imlunestrant With or Without Abemaciclib in Advanced Breast Cancer: Updated Efficacy Results From the Phase 3 EMBER-3 Trial

ByKomal L. Jhaveri,Patrick Neven, MD, PhD,Monica Lis Casalnuovo,Sung-Bae Kim,Eriko Tokunaga,Phillippe Aftimos,Cristina Saura,Joyce O’Shaughnessy, MD,Nadia Harbeck, MD, PhD,Lisa A. Carey, MD,Giuseppe Curigliano,Junichiro Watanabe,Elgene Lim, MBBS, FRACP, PhD,Juan Huang,Qingyuan Zhang,Antonio Llombart-Cussac,Chiun-Sheng Huang,Bhardwaj Desai,Xuejing Aimee Wang,Shanshan Cao,Francois Clement Bidard

100 Imlunestrant Plus Abemaciclib Versus Fulvestrant Plus Abemaciclib in Estrogen Receptor Positive (ER+), Human Epidermal Growth Factor Receptor 2 Negative (HER2–) Advanced Breast Cancer (ABC): An Indirect Treatment Comparison (ITC) of Three Phase 3 Trials

ByKomal L. Jhaveri,Francois Clement Bidard,Kevin Kalinsky, MD, MS,Patrick Neven, MD, PhD,Hope S. Rugo, MD,Sara M. Tolaney, MD, MPH,Lacey Litchfield,Christoph Cramer von Laue,Sory Traore,Francisco Sapunar,Yujia Li,Joyce O’Shaughnessy, MD

101 Patient-Reported Outcomes (PROs) in Patients With ER+, HER2- Advanced Breast Cancer (ABC) Treated with Imlunestrant, Investigator’s Choice Standard Endocrine Therapy, or Imlunestrant+Abemaciclib: Results From the Phase III EMBER-3 Trial

ByGiuseppe Curigliano,Joyce O'Shaughnessy, MD,François-Clément Bidard,Sung-Bae Kim,Eriko Tokunaga,Philippe Aftimos,Cristina Saura,Lisa A. Carey, MD,Meena Okera,Everton Melo,Flora Zagouri,Manuel Ernesto Magallanes Maciel,Nuri Karadurmus,Shakeela Bahadur,Rebecca M Speck,Xuejing Aimee Wang,Suzanne Young,Komal L. Jhaveri,Nadia Harbeck, MD, PhD

102 Imlunestrant (imlu) With or Without Abemaciclib (abema) in Advanced Breast Cancer (ABC): Safety Analyses From the Phase III EMBER-3 Trial

ByJoyce O’Shaughnessy, MD,Francois Clement Bidard,Patrick Neven, MD, PhD,Monica Lis Casalnuovo,Philippe Aftimos,Cristina Saura,Nadia Harbeck, MD, PhD,Lisa A. Carey, MD,Giuseppe Curigliano,J A Garcia-Saenz,Maria Fernandez Abad,Larissa de Paula,Yeon Hee Park,Ozgur Ozyilkan,Maria Munoz,Sabrina Formentini,Emily Barrett,Shanshan Cao,Aarti Chawla,Komal L. Jhaveri