Enhanced toxicity with CDK 4/6 inhibitors and palliative radiotherapy: Non-consecutive case series and review of the literature

Steven David, Gwo Ho, Daphne Day, Marion Harris, Jennifer Tan, Shom Goel, Gerard G. Hanna, Ranjana Srivastava, Gill Kruss, Lachlan McDowell, Michelle White

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19 Citations (Scopus)


Current first-line systemic treatment in most patients with metastatic hormone receptor-positive, HER-2 negative breast cancer is an aromatase inhibitor in combination with a cyclin dependant kinase (CDK) 4/6 inhibitor. Frequently, these patients require palliative radiotherapy (RT) for symptomatic disease management. There is a paucity of data on the safety of combining a CDK 4/6 inhibitor with palliative RT, with conflicting case reports in the literature. We report on 5 cases at our institution where enhanced radiotherapy toxicity was observed when palliative doses of RT was delivered during or prior to treatment with a CDK 4/6 inhibitor. After review of pre-clinical and mechanistic data, we hypothesise that the effects of CDK4/6 inhibition on normal tissue and the tumour microenvironment may impede tissue recovery and exacerbate acute radiation and radiation recall toxicities. Further studies are required to clarify the potential toxicities of this combination. Clinicians should consider the potential risks when combining CDK 4/6 inhibitors with palliative RT and individualise patient management accordingly.

Original languageEnglish
Article number100939
Number of pages7
JournalTranslational Oncology
Issue number1
Publication statusPublished - Jan 2021


  • CDK 4/6 inhibitor
  • Palliative
  • Radiation recall
  • Radiotherapy
  • Toxicity

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