Cabozantinib shows promise for bone metastases in HR+ breast cancer

  • Xu J & al.
  • Oncologist
  • 28 May 2020

  • curated by Miriam Davis, PhD
  • Univadis Clinical Summaries
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Takeaway

  • In a phase 2 trial of cabozantinib, a potent oral multireceptor tyrosine kinase inhibitor, bone metastases showed a partial response in 38% of patients with hormone receptor (HR)-positive breast cancer.

Why this matters

  • Up to 75% of patients with metastatic breast cancer have bone metastases, and that percentage is even higher in the subgroup with HR+ cancers.
  • This phase 2 trial of cabozantinib is promising enough to warrant progression to a phase 3 trial.

Study design

  • Phase 2 trial (N=52) of cabozantinib with a starting dose of 100 mg, which was subsequently reduced to 60 mg/day for 12 weeks.
  • Primary outcome: response on an isotope bone scan, measured by percentage change from baseline according to 4 categories:
    • Complete response.
    • Partial response (≥30% reduction).
    • Stable disease (between
    • Progressive disease (≥20% increase).
  • Funding: Exelixis, Inc.

Key results

  • 38.5% of 52 patients had partial response; 11.5% had stable disease.
  • 36.5% of patients discontinued by 12 weeks because of early progression or unacceptable toxicity.
  • Median PFS was 4.3 months.
  • Median OS was 19.6 months.
  • Most frequent grade 3 or 4 toxicities were:
    • Hypertension (10%).
    • Anorexia (6%).
    • Diarrhea (6%).
    • Fatigue (4%).
    • Hypophosphatemia (4%).

Limitations

  • High rate of discontinuations.
  • Small sample.
  • Single-group, open-label design.