SABCS 2019 – HER2+ breast cancer: add-on pertuzumab shows clinically relevant benefit in some patients


  • Ben Gallarda
  • Univadis
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Takeaway

  • Postoperative pertuzumab+trastuzumab+chemotherapy yielded a nonsignificant but clinically relevant 4.5% increase in invasive DFS (iDFS) in patients with early human epidermal growth factor receptor 2 (HER2)-positive, node-positive operable breast cancer vs trastuzumab+chemotherapy.

Why this matters

  • As the follow-up of the APHINITY trial continues, greater benefits for the specific subgroup with node-positive disease are emerging.
  • Because the iDFS gap widened between groups with and without pertuzumab between the primary and second interim analyses in highlighted subpopulations, future planned interim and final analyses are expected to resolve the iDFS benefit more clearly.

Key results

  • Analysis presented as descriptive (no statistical significance with second interim OS analysis requiring P=.0012).
  • Pertuzumab group had fewer deaths: 125 (5.2%) vs 147 (6.1%).
  • In pertuzumab vs placebo group:
    • OS: HR, 0.85 (95% CI, 0.67-1.07).
    • 6-year OS: 94.8% vs 93.9% (0.9% difference).
    • iDFS: HR, 0.76 (95% CI, 0.64-0.91).
    • Overall 6-year iDFS: 90.6% vs 87.8% (2.8% difference).
    • 6-year iDFS in node-positive patients: 87.9% vs 93.4% (4.5% difference [95% CI, 1.9%-7.1%]); HR, 0.72 (95% CI, 0.59-0.87).
  • No pertuzumab benefit was seen in the node-negative population.
  • No new safety issues reported.

Study design

  • Planned secondary interim analysis of the double-blind, placebo-controlled APHINITY trial.
  • Patients with operable HER2-positive early breast cancer were randomly assigned to adjuvant chemotherapy+trastuzumab+pertuzumab or chemotherapy+trastuzumab+placebo.
  • Funding: Hoffmann-La Roche.

Limitations

  • Data are still immature.
  • Findings were presented at a conference without peer review.

Expert commentary

  • Senior researcher Dr Martine Piccart, cofounder of the Breast International Group and Scientific Director Institut Jules Bordet in Brussels, said results should be taken in the context of what is expected in the curative setting and "6-year data from APHINITY trial did not meet stringent significance cutoff, but “the benefit we see here is considered of really significant clinical value”.
  • She also stated that 94% OS at 6 years in this population with a very aggressive breast cancer subtype is “excellent”.