Incidence and Severity of Myelosuppression With Palbociclib After Palliative Bone Radiation in Advanced Breast Cancer: A Single Center Experience and Review of Literature

Haval Norman, Kimberley T. Lee, Vered Stearns, Sara R. Alcorn, Neha S. Mangini

Research output: Contribution to journalArticlepeer-review

5 Scopus citations


BACKGROUND: Palbociclib is a cyclin-dependent kinase (CDK) 4/6 inhibitor with a primary toxicity of myelosuppression, especially neutropenia, due to cytostatic CDK6 inhibition on bone marrow. Preclinical studies suggest palbociclib may enhance radiation toxicity, but this was only evaluated in limited case series of palliative radiotherapy and not specific to radiation targeting bony metastases.

PATIENTS AND METHODS: This was a single institution retrospective cohort study. We included female patients who initiated palbociclib for advanced breast cancer between 2015 and 2019. The primary exposure was receipt of palliative radiation to bony metastases within 1 year prior to starting palbociclib. The primary outcome was the incidence and severity of myelosuppression during cycle one. Secondary outcomes include treatment interruptions and cycle 2 dose reductions, with subgroup analysis of radiation timing, type, dose, and location.

RESULTS: Of the 247 patients, 47 received radiation to bone metastases. Only absolute lymphocyte count (ALC) after cycle one of palbociclib was significantly lower in the group receiving radiation (median ALC 0.84 vs. 1.10 K/mm 3, P < .001), with similar rates of neutropenia, anemia, and thrombocytopenia. Patients who received ≥10 fractions radiation were more likely to have cycle one interrupted than those receiving shorter radiation courses (42.9% vs. 11.1%, P = .03). No radiation characteristics were associated with other hematologic toxicities or dose reduction.

CONCLUSION: Palliative bone radiation within 1 year prior to palbociclib initiation was associated with greater lymphopenia during the first cycle than patients unexposed to radiation, but not neutropenia, anemia, or thrombocytopenia that would modify treatment.

Original languageEnglish (US)
Pages (from-to)e65-e73
JournalClinical Breast Cancer
Issue number1
StatePublished - Jan 2022
Externally publishedYes

Bibliographical note

Funding Information:
The authors declare the following financial interests/personal relationships: KTL: Received research grants to institution from Pfizer Inc. and has collaborated with Eli Lilly and Company in the role of an unpaid consultant in the past 12 months. VS: Received research grants to institution from Abbvie, Biocept, Pfizer Inc., Novartis, and Puma Biotechnology. Member, Data Safety Monitoring Board, Immunomedics, Inc. SRA: Received research grant from Radiation Oncology Institute.

Publisher Copyright:
© 2021


  • CDK inhibitors
  • Endocrine therapy
  • Hormone receptor-positive
  • Human epidermal growth factor receptor 2-negative
  • Metastatic breast cancer
  • Humans
  • Middle Aged
  • Incidence
  • Neutropenia/chemically induced
  • Dose-Response Relationship, Drug
  • Patient Acuity
  • Pyridines/adverse effects
  • Piperazines/adverse effects
  • Antineoplastic Agents/adverse effects
  • Bone Marrow Diseases/chemically induced
  • Female
  • Retrospective Studies
  • Breast Neoplasms/drug therapy

PubMed: MeSH publication types

  • Review
  • Research Support, Non-U.S. Gov't
  • Journal Article


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