The implementation of CDK 4/6 inhibitors and its impact on treatment choices in HR+/HER2-advanced breast cancer patients: A study of the Dutch SONABRE Registry

M. Meegdes, S.M.E. Geurts, F.L.G. Erdkamp, M.W. Dercksen, B.E.P.J. Vriens, K.N.A. Aaldering, M.J.A.E. Pepels, L.M.H. Winkel, N.J.A. Teeuwen, M. Boer, V.C.G. Tjan-Heijnen*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review


In August 2017, cyclin-dependent kinase 4/6 (CDK4/6) inhibitors combined with endocrine therapy have been reimbursed in the Netherlands for patients with hormone receptor positive (HR+), HER2 negative (HER2-) advanced breast cancer (ABC). This study evaluates the implementation of CDK4/6 inhibitors and changes in treatment choices in the Netherlands. All patients diagnosed with HR+/HER2- ABC in 2009 to 2018 in seven hospitals were selected from the Southeast Netherlands Advanced Breast cancer (SONABRE) registry. The 2-year cumulative use of CDK4/6 inhibitors since reimbursement date (August 2017) was assessed using competing-risk methodology in two cohorts. The first cohort included patients with ABC diagnosis between August 2017 and December 2018. The second cohort included patients with ABC diagnosis between 2009 and August 2017, and still alive on August 1, 2017. In addition, treatment choices in the first three lines of therapy in calendar years 2009 to 2018 were evaluated for the total study population. Among patients diagnosed since August 2017 (n = 214), 50% (95% confidence interval [CI] = 43-57) received CDK4/6 inhibitors within 2 years beyond diagnosis. Of eligible patients diagnosed before August 2017 (n = 417), 31% (95% CI = 27-36) received CDK4/6 inhibitors within 2 years following reimbursement. Another 20% of both cohorts are still CDK4/6 inhibitor naive and on first-line therapy. The use of chemotherapy decreased in first two lines of therapy between 2009 and 2018 (first-line: 29%-13%; second-line: 26%-19%). The implementation rate of CDK4/6 inhibitors since reimbursement is currently 50% within 2 years beyond diagnosis and is expected to increase further. The implementation of targeted therapy decreased the use of chemotherapy as first-line therapy.
Original languageEnglish
Pages (from-to)124-131
Number of pages8
JournalInternational Journal of Cancer
Issue number1
Early online date14 Sept 2021
Publication statusPublished - 1 Jan 2022


  • 6 inhibitors
  • CDK4
  • breast cancer
  • implementation
  • metastatic disease
  • real-world

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