Initial experience with CDK4/6 inhibitor-based therapies compared to antihormone monotherapies in routine clinical use in patients with hormone receptor positive, HER2 negative breast cancer - Data from the PRAEGNANT research network for the first 2 years of drug availability in Germany.

Purpose: Treatment with CDK4/6 inhibitors and endocrine therapy (CDK4/6i + ET) is a standard for patients with advanced hormone receptor-positive, HER2-negative (HR + HER2-) breast cancer (BC). However, real-world data on the implementation of therapy usage, efficacy, and toxicity have not yet been reported.
Methods: The PRAEGNANT registry was used to identify advanced HR + HER2- BC patients (n = 1136). The use of chemotherapy, ET, everolimus + ET, and CDK4/6i + ET was analyzed for first-line, second-line, and third-line therapy. Progression-free survival (PFS) and overall survival (OS) were also compared between patients treated with CDK4/6i + ET and ET monotherapy. Also toxicity was assessed.
Results: CDK4/6i + ET use increased from 38.5% to 62.7% in the first 2 years after CDK4/6i treatment became available (November 2016). Chemotherapy and ET monotherapy use decreased from 2015 to 2018 from 42.2% to 27.2% and from 53% to 9.5%, respectively. In this early analysis no statistically significant differences were found comparing CDK4/6i + ET and ET monotherapy patients with regard to PFS and OS. Leukopenia was was seen in 11.3% of patients under CDK4/6i + ET and 0.5% under ET monotherapy.
Conclusions: In clinical practice, CDK4/6i + ET has been rapidly implemented. A group of patients with a more unfavorable prognosis was possibly treated in the real-world setting than in the reported randomized clinical trials. The available data suggest that longer follow-up times and a larger sample size are required in order to identify differences in survival outcomes. Studies should be supported that investigate whether chemotherapy can be avoided or delayed in this patient population by using CDK4/6i + ET.
Competing Interests: Declaration of competing interest A.S. received honoraria from Roche, AstraZeneca, Aurikamed GmbH, Celgene, ClinSol Research GmbH, Connectmedica Sp.Z o.o., Deutsche Gesellschaft für Senologie GmbH, if-kongress management gmbh, I-MED Institute GmbH, Lilly Deutschland GmbH, Medicultus GmbH, med publico GmbH, MSD Sharp & Dohme GmbH, onkowissen.de GmbH, Pfizer GmbH, Schattauer Verlag GmbH, Promedicis GmbH, Tesaro Bio Germany GmbH, W. Zuckschwerdt Verlag GmbH. J.E. received honoraria from AstraZeneca, Celgene, Novartis, Lilly, Pfizer, Pierre Fabre, Roche and TEVA and travel support from Celgene, Pfizer, TEVA, and Pierre Fabre. D.L. received honoraria from Amgen, AstraZeneca, Celgene, Lilly, Loreal, MSD, Novartis, Pfizer, Tesaro, Teva. M.W.B reports support from Novartis, Merck Sharp & Dohme, AstraZeneca, Roche, Amgen, Eisai, paid to his institution. E.B. received honoraria from Novartis, Celgene, Riemser, Pfizer, Hexal, Amgen, onkowissen.de for consulting, clinical research management or medical education activities. P.A.F. received honoraria from Novartis, Pfizer, Roche, Amgen, Celgene, Daiichi-Sankyo, AstraZeneca, Merck-Sharp & Dohme, Eisai, Puma and Teva. His institution conducts research with funding from Novartis and Biontech. T.N.F. reports personal fees from Roche, personal fees from Novartis, personal fees from Pfizer, personal fees from Daichii Sankyo, personal fees from Lilly, personal fees from MSD, outside the submitted work. P.H. received honoraria, unrestricted educational grants and research funding from Amgen, AstraZeneca, Eli Lilly, MSD, Novartis, Pfizer, and Roche. A.D.H. received honoraria from Teva, GenomicHealth, Celgene, AstraZeneca, Novartis, Pfizer, and Roche. C.H. received honoraria from Amgen, Celgene, Oncovis, Roche, and Pfizer. J.H. received honoraria from Astra Zeneca, MSD, Lilly, travel grants from Novartis and research grants from Novartis, Celgene. E.R. reports personal fees from Roche, Pfizer, Amgen, Novartis, Tesaro, Astra Zeneca, Celgene, Pierre Fabre and Riemer, non-financial support from Olympus GmbH, personal fees from Riemser, outside the submitted work. W.J. received research grants and honoroaria from Novartis, Pfizer, Amgen, Chugai, Roche, Genomic-Health, AstraZeneca, Lilly. H.-C.K. received honoraria from Carl Zeiss meditec, TEVA, Theraclion, Novartis, Amgen, AstraZeneca, Pfizer, Janssen-Cilag, GSK, LIV Pharma, and Genomic Health. C.M.K. received honoraria from Amgen, Axios, Roche, Teva, Novartis, MSD Sharp & Dohme, Mundipharma, NewCo, Pfizer, Riemser, and ZytoService, research grants from Amgen, Axios, Novartis, MSD Sharp & Dohme, NewCo, Pfizer, and ZytoService, and travel support from Amgen, Paxman Inc., PharmaMar, and Pfizer. M.P.L. has participated on advisory boards for AstraZeneca, MSD, Novartis, Pfizer, Eisai, Genomic Health, Tesaro and Roche and has received honoraria for lectures from MSD, Lilly, Roche, Novartis, Pfizer, Genomic Health, AstraZeneca, medac and Eisai. V.M. received speaker honoraria from Amgen, Astra Zeneca, Celgene, Daiichi-Sankyo, Eisai, Pfizer, Novartis, Roche, Teva, Janssen-Cilag and consultancy honoraria from Genomic Health, Hexal, Roche, Pierre Fabre, Amgen, Novartis, MSD, Daiichi-Sankyo, Eisai, Lilly, Tesaro and Nektar. N.N. received consultancy honoraria from Janssen-Cilag and travel support from Novartis. F.O. received speaker and consultancy honoraria from Amgen, AstraZeneca, Bayer, BMS, Boehringer, Celgene, Cellex, Chugai, Gilead, Hexal, Ipsen, Janssen-Cilag, Merck, MSD, Novartis, Riemser, Roche, Tesaro, Teva. H.T. received honoraria from Novartis, Roche, Celgene, TEVA, and Pfizer and travel support. F.-A. T. received honoraria from Astra Zeneca, Genomic Health and Novartis. C.T. received honoraria from Amgen, Astra-Zeneca, Celgene, Novartis, Pfizer, and Roche. M.U. reports support paid to his institution from Abbvie, Amgen GmbH München, Astra Zeneca, BMS, Celgene GmbH München, Daiji Sankyo, Eisai GmbH München, Janssen Cilag, Johnsen&Johnsen, Lilly Deutschland, Lilly Int., MSD Merck, Mundipharma, Myriad Genetics GmbH Zürich, Odonate, Pfizer GmbH Berlin, PUMA Biotechnology, Riemser, Roche Pharma AG, Grenzach Wyhlen, Sanofi Aventis Deutschland GmbH, Sividon Diagnostics Köln, TEVA Pharmaceuticals Ind. Ltd. und. Berlin(.)P.W. received honoraria from Amgen, AstraZeneca, Merck Sharp & Dohme, Novartis, Pfizer, PharmaMar, Roche, TEVA, Eisai Clovis and Tesaro. She participated in advisory boards of Amgen, AstraZeneca, Merck Sharp & Dohme, Novartis, Pfizer, PharmaMar, Roche, TEVA, Eisai Clovis and Tesaro. Her institution received research grants from Amgen, AstraZeneca, MSD, Novartis, Pfizer, Pharmamar, Clovis and Tesaro. R.W. received honoraria from Agendia, Amgen, Astra Zeneca, Boeringer Ingelheim, Carl Zeiss, Celgene, Daiichi-Sankyo, Esai, Genomic Health, Glaxo Smith Kline, Lilly, MSD, Mundipharma, Nanostring, Novartis, Odonate, Paxman, Palleos, Pfizer, Pierre Fabre, PumaBiotechnolgogy, Riemser, Roche, Sandoz/Hexal, Seattle Genetics, Tesaro Bio, Teva. M.W. received speaker honoraria from AstraZeneca, Celgene, and Novartis. S.Y.B. reports personal fees from Novartis and Pfizer, both outside the submitted work. All remaining authors (J.S., E.K., M.G., L.H., B.V., D.W.) have declared that they do not have any conflicts of interest.
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