In recent years, new targeted therapies have been developed to treat patients with hormone receptor-positive (HR+)/human epidermal growth factor receptor 2-negative (HER2-) breast cancer. Some of these therapies have not just become the new therapy standard but also led to significantly longer overall survival rates. The cyclin-dependent kinase 4 and 6 inhibitors (CDK4/6i) have become the therapeutic standard for first-line therapy. Around 70 - 80% of patients are treated with a CDK4/6i. In recent years, a number of biomarkers associated with progression, clonal selection or evolution have been reported for CDK4/6i and their endocrine combination partners. Understanding the mechanisms behind treatment efficacy and resistance is important. A better understanding could contribute to planning the most effective therapeutic sequences and utilizing basic molecular information to overcome endocrine resistance. One study with large numbers of patients which aims to elucidate these mechanisms is the Comprehensive Analysis of sPatial, TempORal and molecular patterns of ribociclib efficacy and resistance in advanced Breast Cancer patients (CAPTOR BC) trial. This overview summarizes the latest clinical research on resistance to endocrine therapies, focusing on CDK4/6 inhibitors and discussing current study concepts.
Competing Interests: Conflict of Interest/Interessenkonflikt B. A. received honoria and travel grants from AstraZeneca, Gilead, Genomic Health, Roche, Novartis, Celgene, Lilly, MSD, Eisai, Teva, Tesaro, Onkowissen, Daiichi Sankyo and Pfizer. C. B. is an employee of Novartis Deutschland GmbH. E. B. received honoraria from Gilead, Ipsen, Sanofi, Sandoz, SunPharma, AstraZeneca, Novartis, Hexal, BMS, Lilly, Pfizer, Roche, MSD, B Braun and onkowissen.de for clinical research management and/or medical education activities. S. Y. B. has received honoraria from Roche, Novartis, Pfizer, MSD, Teva, AstraZeneca. N. D. has received honoraria from MSD, Roche, AstraZeneca, Teva, Pfizer, Novartis, Seagen, Gilead, MCI Healthcare. P. A. F. received honoraria from Novartis, Pfizer, Roche, Amgen, Celgene, onkowissen.de, Daiichi Sankyo, AstraZeneca, Merck Sharp & Dohme, Eisai, Puma and Teva. His institution conducts research with funding from Novartis and BioNtech. T. E. has received honoraria from AstraZeneca, Eli Lilly, Daiichi Sankyo, Gilead, GSK, MSD, Novartis, Pfizer, Roche, Stemline. T. N. F. has participated on advisory boards for Amgen, Daiichi Sankyo, Novartis, Pfizer, and Roche and has received honoraria for lectures from Amgen, Celgene, Daiichi Sankyo, Roche, Novartis and Pfizer. A. D. H. received speaker and consultancy honoraria from AstraZeneca, Genomic Health, Roche, Novartis, Celgene, Lilly, MSD, Eisai, Teva, Tesaro, Daiichi Sankyo, Hexal and Pfizer. C. C. H. has received honoraria from Pfizer, Novartis, Roche, AstraZeneca, Eisai and Daiichi Sankyo. H. H. received speaker honoraria from Novartis. H. N. received honoraria for lectures and/or consulting from Amgen, AstraZeneca, Daiichi Sankyo, Exact Sciences, Gilead, Lilly, MSD, Mylan, Novartis, Pierre Fabre, Pfizer, Roche, Sandoz, Seagen. W. J. has received research grants and/or honoraria from Sanofi Aventis, Daiichi Sankyo, Novartis, Roche, Pfizer, Lilly, AstraZeneca, Chugai, GSK, Eisai, Cellgene and Johnson & Johnson. H.-C. K. has received honoraria from Pfizer, Novartis, Seagen, Roche, Genomic Health/Exact Sciences, Amgen, AstraZeneca, Riemser, Carl Zeiss Meditec, Teva, Theraclion, Janssen-Cilag, GSK, LIV Pharma, Lilly, SurgVision, Onkowissen, Gilead, Daiichi Sankyo and MSD, travel support from Carl Zeiss Meditec, LIV Pharma, Novartis, Amgen, Pfizer, Daiichi Sankyo, Tesaro and owns stock of Theraclion SA and Phaon Scientific GmbH. D. L. received honoraria from Amgen, AstraZeneca, Eli Lilly, High5md, Gilead, GSK, Loreal, MSD, Novartis, Onkowissen, Pfizer, Seagen, Teva. M. P. L. has participated on advisory boards for AstraZeneca, Lilly, MSD, Novartis, Pfizer, Eisai, Gilead, Exact Sciences, Pierre Fabre, Grünenthal, Daiichi Sankyo, PharmaMar, Roche, SamanTree, Sysmex and Hexal and has received honoraria for lectures from MSD, Lilly, Roche, Novartis, Pfizer, Exact Sciences, Daiichi Sankyo, Grünenthal, pfm, Gilead, AstraZeneca, and Eisai. V. M. received speaker honoraria from Amgen, AstraZeneca, Daiichi Sankyo, Eisai, GSK, Pfizer, MSD, Medac, Novartis, Roche, Teva, Seagen, Onkowissen, high5 Oncology, Medscape, Gilead. Consultancy honoraria from Hexal, Roche, Pierre Fabre, Amgen, ClinSol, Novartis, MSD, Daiichi Sankyo, Eisai, Lilly, Sanofi, Seagen, Gilead. Institutional research support from Novartis, Roche, Seagen, Genentech. Travel grants: Roche, Pfizer, Daiichi Sankyo. B. R. reports research grants from Roche, Menarini, Lilly, Inivata. Honoraria from AZ, Roche. C. R. is an employee of Novartis Deutschland GmbH. A. S. received research grants from Celgene, Roche, honoraria from Amgen, AstraZeneca, Aurikamed, Bayer, Celgene, Clinsol, Connectmedica, Gilead, GSK, I-MED, Lilly, MCI Deutschland, Metaplan, MSD, Nanostring, Novartis, Onkowissen.de, Promedicis, Pfizer, Pierre Fabre, Roche, Seagen, Streamedup, Teva, Tesaro, Thieme and travel support from Celgene, Pfizer, Roche. K. S. received travel support from Gilead and Lilly. F.-A. T. received speaker and consultancy honoraria from AstraZeneca, Genomic Health, Gilead, GSK, Hexal, MSD, Novartis, Onkowissen, Pfizer, Roche, Tesaro. H. T. received honoraria from Novartis, Roche, Celgene, Teva, Pfizer, AstraZeneca and travel support from Roche, Celgene, and Pfizer. M. T. has participated on advisory boards for AstraZeneca, Celgene, Clovis, Daiichi Sankyo, Eisai, Gilead Science, Grünenthal, GSK, Lilly, MSD, Novartis, Organon, Pfizer, Pierre Fabre, Seagen, and Roche and has received honoraria for lectures from Amgen, Aurikamed, Celgene, Clovis, Daiichi Sankyo, Eisai, GSK, Lilly, MSD, Roche, Novartis, Organon, Pfizer, Seagen, Exact Sciences, Viatris, Vifor and AstraZeneca and has received trial funding from Exact Sciences and Endomag Manuscript support was provided by Amgen, ClearCut, pfm medical, Roche, Servier, Vifor. M. U. all honoraria went to the institution/employer: Abbvie, Amgen, AstraZeneca, Daiichi Sankyo, Eisai, Lilly, MSD, Myriad Genetics, Pfizer, Roche, Sanofi Aventis, Novartis, Pierre Fabre, Seagen, Gilead. P. W. has received honoraria from Roche, Novartis, Amgen, AstraZeneca, Pfizer, MSD, Clovis, Tesaro, Celgene, Teva, Eisai, Daiichi Sankyo, Seagen and Eli Lilly. The other authors (L. L. V, M. R., S. H., V. T., I. J.-B., D. A., M. B., M. S., J. R., I. N.) have no conflict of interest to declare for this specific work./ B. A. erhielt Honorare und Reisekosten von AstraZeneca, Gilead, Genomic Health, Roche, Novartis, Celgene, Lilly, MSD, Eisai, Teva, Tesaro, Onkowissen, Daiichi Sankyo und Pfizer. C. B. ist Angestellte der Firma Novartis Deutschland GmbH. E. B. erhielt Honorare von Gilead, Ipsen, Sanofi, Sandoz, SunPharma, AstraZeneca, Novartis, Hexal, BMS, Lilly, Pfizer, Roche, MSD, B Braun und onkowissen.de für klinisches Forschungsmanagement und/oder Aktivitäten der medizinischen Fortbildung. S. Y. B. erhielt Honorare von Roche, Novartis, Pfizer, MSD, Teva, AstraZeneca. N. D. erhielt Honorare von MSD, Roche, AstraZeneca, Teva, Pfizer, Novartis, Seagen, Gilead, MCI Healthcare. P. A. F. erhielt Honorare von Novartis, Pfizer, Roche, Amgen, Celgene, onkowissen.de, Daiichi Sankyo, AstraZeneca, Merck Sharp & Dohme, Eisai, Puma und Teva. Seine Institution betreibt Forschung mit finanzieller Unterstützung von Novartis und BioNtech. T. E. erhielt Honorare von AstraZeneca, Eli Lilly, Daiichi Sankyo, Gilead, GSK, MSD, Novartis, Pfizer, Roche, Stemline. T. N. F. hat in Beiräten mitgewirkt für Amgen, Daiichi Sankyo, Novartis, Pfizer und Roche und hat Vortragshonorare erhalten von Amgen, Celgene, Daiichi Sankyo, Roche, Novartis und Pfizer. A. D. H. erhielt Sprecher- und Beraterhonorare von AstraZeneca, Genomic Health, Roche, Novartis, Celgene, Lilly, MSD, Eisai, Teva, Tesaro, Daiichi Sankyo, Hexal und Pfizer. C. C. H. erhielt Honorare von Pfizer, Novartis, Roche, AstraZeneca, Eisai und Daiichi Sankyo. H. H. erhielt Sprecherhonorare von Novartis. H. N. erhielt Vortragshonorare und/oder Honorare für Beratertätigkeiten vn Amgen, AstraZeneca, Daiichi Sankyo, Exact Sciences, Gilead, Lilly, MSD, Mylan, Novartis, Pierre Fabre, Pfizer, Roche, Sandoz, Seagen. W. J. erhielt Forschungsstipendien und/oder Honorare von Sanofi Aventis, Daiichi Sankyo, Novartis, Roche, Pfizer, Lilly, AstraZeneca, Chugai, GSK, Eisai, Cellgene und Johnson & Johnson. H.-C. K. erhielt Honorare von Pfizer, Novartis, Seagen, Roche, Genomic Health/Exact Sciences, Amgen, AstraZeneca, Riemser, Carl Zeiss Meditec, Teva, Theraclion, Janssen-Cilag, GSK, LIV Pharma, Lilly, SurgVision, Onkowissen, Gilead, Daiichi Sankyo and MSD, Reisekostenzuschüsse von Carl Zeiss Meditec, LIV Pharma, Novartis, Amgen, Pfizer, Daiichi Sankyo, Tesaro und besitzt Aktien von Theraclion SA und Phaon Scientific GmbH. D. L. erhielt Honorare von Amgen, AstraZeneca, Eli Lilly, High5md, Gilead, GSK, Loreal, MSD, Novartis, Onkowissen, Pfizer, Seagen, Teva. M. P. L. hat in Beiräten mitgewirkt für AstraZeneca, Lilly, MSD, Novartis, Pfizer, Eisai, Gilead, Exact Sciences, Pierre Fabre, Grünenthal, Daiichi Sankyo, PharmaMar, Roche, SamanTree, Sysmex und Hexal und erhielt Vortragshonorare von MSD, Lilly, Roche, Novartis, Pfizer, Exact Sciences, Daiichi Sankyo, Grünenthal, pfm, Gilead, AstraZeneca und Eisai. V. M. erhielt Sprecherhonorare von Amgen, AstraZeneca, Daiichi Sankyo, Eisai, GSK, Pfizer, MSD, Medac, Novartis, Roche, Teva, Seagen, Onkowissen, high5 oncology, Medscape, Gilead. Beraterhonorare von Hexal, Roche, Pierre Fabre, Amgen, ClinSol, Novartis, MSD, Daiichi Sankyo, Eisai, Lilly, Sanofi, Seagen, Gilead, institutionelle Forschungsförderung von Novartis, Roche, Seagen, Genentech. Reisekostenzuschüsse von Roche, Pfizer, Daiichi Sankyo. B. R. erhielt Forschungsstipendien von Roche, Menarini, Lilly, Inivata, Honorare von AZ, Roche. C. R. ist Angestellter der Firma Novartis Deutschland GmbH. A. S. erhielt Forschungsstipendien von Celgene, Roche, Honorare von Amgen, AstraZeneca, Aurikamed, Bayer, Celgene, Clinsol, Connectmedica, Gilead, GSK, I-MED, Lilly, MCI Deutschland, Metaplan, MSD, Nanostring, Novartis, Onkowissen.de, Promedicis, Pfizer, Pierre Fabre, Roche, Seagen, Streamedup, Teva, Tesaro, Thieme und Reisekostenzuschüsse von Celgene, Pfizer, Roche. K. S. erhielt Reisekostenzuschüsse von Gilead und Lilly. F.-A. T. erhielt Sprecher- und Beraterhonorare von AstraZeneca, Genomic Health, Gilead, GSK, Hexal, MSD, Novartis, Onkowissen, Pfizer, Roche, Tesaro. H. T. erhielt Honorare von Novartis, Roche, Celgene, Teva, Pfizer, AstraZeneca und Reisekostenzuschüsse von Roche, Celgene und Pfizer. M. T. hat in Beiräten mitgewirkt für AstraZeneca, Celgene, Clovis, Daiichi Sankyo, Eisai, Gilead Science, Grünenthal, GSK, Lilly, MSD, Novartis, Organon, Pfizer, Pierre Fabre, Seagen und Roche, erhielt Vortragshonorare von Amgen, Aurikamed, Celgene, Clovis, Daiichi Sankyo, Eisai, GSK, Lilly, MSD, Roche, Novartis, Organon, Pfizer, Seagen, Exact Sciences, Viatris, Vifor und AstraZeneca und erhielt Studienfinanzierung von Exact Sciences und Endomag; Unterstützung für das Manuskript kam von Amgen, ClearCut, pfm medical, Roche, Servier, Vifor. M. U. Alle Honorare wurden an die Institution/den Arbeitergeber abgeführt: Abbvie, Amgen, AstraZeneca, Daiichi Sankyo, Eisai, Lilly, MSD, Myriad Genetics, Pfizer, Roche, Sanofi Aventis, Novartis, Pierre Fabre, Seagen, Gilead. P. W. erhielt Honorare von Roche, Novartis, Amgen, AstraZeneca, Pfizer, MSD, Clovis, Tesaro, Celgene, Teva, Eisai, Daiichi Sankyo, Seagen und Eli Lilly. Die anderen Autoren und Autorinnen (L. L. V, M. R., S. H., V. T., I. J.-B., D. A., M. B., M. S., J. R., I. N.) haben keine Interessenkonflikte zu melden.
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