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Updated: Jan 31, 2026

An Ex vivo Model to Study Hormone Action in the Human Breast
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CDK4/6 inhibition versus mTOR blockade as second-line strategy in postmenopausal patients with hormone

Hong-Wei Huang1, Li-Sheng Huang2, Qi-Ni Xu3

  • 1The Seventh Department of Surgery, Puning People's Hospital, Puning.

Medicine
|January 5, 2019
PubMed
Abstract

Insights

Cyclin-dependent kinase 4/6 (CDK4/6) inhibitors and mammalian target of rapamycin (mTOR) inhibitors show similar efficacy in advanced breast cancer. CDK4/6 inhibitors offer a more favorable toxicity profile, leading to fewer treatment discontinuations.

Area of Science:

  • Oncology
  • Pharmacology

Background:

  • Advanced breast cancer often progresses on aromatase inhibitors, necessitating alternative treatments.
  • Cyclin-dependent kinase 4/6 (CDK4/6) inhibitors (palbociclib, abemaciclib) and mammalian target of rapamycin (mTOR) inhibitors (everolimus) can restore endocrine sensitivity.
  • These agents are used in patients with advanced breast cancer progressing on prior aromatase inhibitors.

Purpose of the Study:

  • To compare the efficacy and safety of CDK4/6 inhibitors versus mTOR inhibitors in advanced breast cancer.
  • To evaluate progression-free survival (PFS), objective response rate (ORR), and clinical benefit rate (CBR).

Main Methods:

  • A network meta-analysis was performed on data from six trials including 4063 patients.
  • Searched PubMed and Embase databases for relevant publications from January 2000 to June 2018.
  • Treatments were ranked using P-scores; random-effect or fixed-effect models were applied based on heterogeneity.

Main Results:

  • Palbociclib and abemaciclib combined with fulvestrant showed similar PFS and ORR compared to everolimus plus exemestane.
  • Palbociclib demonstrated improved CBR, while abemaciclib did not show significant improvement.
  • Severe adverse events did not significantly differ between treatment groups.
  • Discontinuation rates due to toxicity were 4% for palbociclib, 15.9% for abemaciclib, and 29% for everolimus.

Conclusions:

  • CDK4/6 inhibitors and mTOR inhibitors exhibit comparable efficacy in advanced breast cancer.
  • CDK4/6 inhibitors are associated with a more favorable toxicity profile, resulting in lower discontinuation rates.
  • These findings support CDK4/6 inhibitors as a preferred treatment option due to better tolerability.

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