Breast Cancer Research (Mar 2019)

PIK3CA alterations and benefit with neratinib: analysis from the randomized, double-blind, placebo-controlled, phase III ExteNET trial

  • Stephen K. L. Chia,
  • Miguel Martin,
  • Frankie A. Holmes,
  • Bent Ejlertsen,
  • Suzette Delaloge,
  • Beverly Moy,
  • Hiroji Iwata,
  • Gunter von Minckwitz,
  • Janine Mansi,
  • Carlos H. Barrios,
  • Michael Gnant,
  • Zorica Tomašević,
  • Neelima Denduluri,
  • Robert Šeparović,
  • Sung-Bae Kim,
  • Erik Hugger Jakobsen,
  • Vernon Harvey,
  • Nicholas Robert,
  • John Smith,
  • Graydon Harker,
  • Bo Zhang,
  • Lisa D. Eli,
  • Yining Ye,
  • Alshad S. Lalani,
  • Marc Buyse,
  • Arlene Chan

DOI
https://doi.org/10.1186/s13058-019-1115-2
Journal volume & issue
Vol. 21, no. 1
pp. 1 – 9

Abstract

Read online

Abstract Background Neratinib is an irreversible pan-HER tyrosine kinase inhibitor that inhibits PI3K/Akt and MAPK signaling pathways after HER2 receptor activation. The ExteNET study showed that neratinib significantly improved 5-year invasive disease-free survival (iDFS) in women who completed trastuzumab-based adjuvant therapy for early breast cancer (EBC). We assessed the prognostic and predictive significance of PIK3CA alterations in patients in ExteNET. Methods Participants were women aged ≥ 18 years (≥ 20 years in Japan) with stage 1–3c (modified to stage 2–3c in February 2010) operable breast cancer, who had completed (neo)adjuvant chemotherapy plus trastuzumab ≤ 2 years before randomization, with no evidence of disease recurrence or metastatic disease at study entry. Patients were randomized to oral neratinib 240 mg/day or placebo for 1 year. Formalin-fixed, paraffin-embedded primary tumor specimens underwent polymerase chain reaction (PCR) PIK3CA testing for two hotspot mutations in exon 9, one hot-spot mutation in exon 20, and fluorescence in situ hybridization (FISH) analysis for PIK3CA amplification. The primary endpoint (iDFS) was tested with log-rank test and hazard ratios (HRs) estimated using Cox proportional-hazards models. Results Among the intent-to-treat population (n = 2840), tumor specimens were available for PCR testing (991 patients) and PIK3CA FISH (702 patients). Overall, 262 samples were PIK3CA altered: 201 were mutated (77%), 52 (20%) were amplified, and 9 (3%) were mutated and amplified. iDFS was non-significantly worse in placebo-treated patients with altered vs wild-type PIK3CA (HR 1.34; 95% CI 0.72–2.50; P = 0.357). Neratinib’s effect over placebo was significant in patients with PIK3CA-altered tumors (HR 0.41; 95% CI 0.17–0.90, P = 0.028) but not PIK3CA wild-type tumors (HR 0.72; 95% CI 0.36–1.41; P = 0.34). The interaction test was non-significant (P = 0.309). Conclusions Although there was a greater absolute risk reduction associated with neratinib treatment of patients with PIK3CA-altered tumors in ExteNET, current data do not support PIK3CA alteration as a predictive biomarker of response to neratinib in HER2-positive EBC. Trial registration ClinicalTrials.gov, NCT00878709. Trial registered April 9, 2009.

Keywords