CDK4/6 inhibitors in HR+/HER2- advanced/metastatic breast cancer: a systematic literature review of real-world evidence studies

Future Oncol. 2021 Jun;17(16):2107-2122. doi: 10.2217/fon-2020-1264. Epub 2021 Mar 5.


Background: This review aims to qualitatively summarize the published real-world evidence (RWE) for CDK4/6 inhibitors (CDK4/6i) approved for treating HR+, HER2-negative advanced/metastatic breast cancer (HR+/HER2- a/mBC). Materials & methods: A systematic literature review was conducted to identify RWE studies of CDK4/6i in HR+/HER2- a/mBC published from 2015 to 2019. Results: This review identified 114 studies, of which 85 were only presented at scientific conferences. Most RWE studies investigated palbociclib and demonstrated improved outcomes. There are limited long-term and comparative data between CDK4/6i and endocrine monotherapy, and within the CDK4/6i class. Conclusion: Available RWE suggests that CDK4/6i are associated with improved outcomes in HR+/HER2- a/mBC, although additional studies with longer follow-up periods are needed.

Keywords: CDK4/6i; biological therapy; breast; metastasis; real-world evidence; systematic literature review.

Publication types

  • Systematic Review

MeSH terms

  • Antineoplastic Combined Chemotherapy Protocols / therapeutic use*
  • Breast Neoplasms / drug therapy*
  • Breast Neoplasms / metabolism
  • Breast Neoplasms / pathology
  • Clinical Trials as Topic
  • Cyclin-Dependent Kinase 4 / antagonists & inhibitors*
  • Cyclin-Dependent Kinase 6 / antagonists & inhibitors*
  • Estrogen Receptor alpha / metabolism*
  • Female
  • Humans
  • Neoplasm Metastasis
  • Neoplasm Staging
  • Receptor, ErbB-2 / metabolism*
  • Receptors, Progesterone / metabolism*
  • Treatment Outcome


  • ESR1 protein, human
  • Estrogen Receptor alpha
  • Receptors, Progesterone
  • ERBB2 protein, human
  • Receptor, ErbB-2
  • CDK4 protein, human
  • CDK6 protein, human
  • Cyclin-Dependent Kinase 4
  • Cyclin-Dependent Kinase 6

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