Biomarker analyses from a placebo-controlled phase II study evaluating erlotinib±onartuzumab in advanced non-small cell lung cancer: MET expression levels are predictive of patient benefit

Abstract

Purpose: In a recent phase II study of onartuzumab (MetMAb), patients whose non-small cell lung cancer (NSCLC) tissue scored as positive for MET protein by immunohistochemistry (IHC) experienced a significant benefit with onartuzumab plus erlotinib (O+E) versus erlotinib. We describe development and validation of a standardized MET IHC assay and, retrospectively, evaluate multiple biomarkers as predictors of patient benefit.

Experimental design: Biomarkers related to MET and/or EGF receptor (EGFR) signaling were measured by IHC, FISH, quantitative reverse transcription PCR, mutation detection techniques, and ELISA.

Results: A positive correlation between IHC, Western blotting, and MET mRNA expression was observed in NSCLC cell lines/tissues. An IHC scoring system of MET expression taking proportional and intensity-based thresholds into consideration was applied in an analysis of the phase II study and resulted in the best differentiation of outcomes. Further analyses revealed a nonsignificant overall survival (OS) improvement with O+E in patients with high MET copy number (mean≥5 copies/cell by FISH); however, benefit was maintained in "MET IHC-positive"/MET FISH-negative patients (HR, 0.37; P=0.01). MET, EGFR, amphiregulin, epiregulin, or HGF mRNA expression did not predict a significant benefit with onartuzumab; a nonsignificant OS improvement was observed in patients with high tumor MET mRNA levels (HR, 0.59; P=0.23). Patients with low baseline plasma hepatocyte growth factor (HGF) exhibited an HR for OS of 0.519 (P=0.09) in favor of onartuzumab treatment.

Conclusions: MET IHC remains the most robust predictor of OS and progression-free survival benefit from O+E relative to all examined exploratory markers.

Trial registration: ClinicalTrials.gov NCT01456325.

Conflict of interest statement

Disclosure of Potential Conflicts of Interest

H. Koeppen has ownership interest in Roche. L. Fu is an employee of Roche. T. Januario, M. Lazarov, and L.C. Amler are employees of Genentech. I.I. Wistuba reports receiving a commercial research grant from Genentech/ Roche and is a consultant/advisory board member for Genentech/Roche and Ventana. S.C. Phan is an employee of and has ownership interest (including patents) in Genentech. No potential conflicts of interest were disclosed by the other authors.

©2014 American Association for Cancer Research.

Figures

Figure 1

Characterization of SP44. A, representative images depicting the range of SP44 staining intensities (negative, weak, moderate, and strong staining) in malignant NSCLC tissues. B, relationship of SP44 immunohistochemical staining intensity and MET protein levels by Western blotting in NSCLC cell lines using two anti-MET antibodies; four representative cell lines and staining intensity are shown. C, correlation of IHC score with MET mRNA levels in NSCLC tissues determined by qRT-PCR.

Figure 2

Evaluation of patient outcomes with O+E treatment based upon alternative IHC cutoffs. A, the forest plot for PFS from OAM4558g according to different IHC intensities and different proportional cutoffs (10%, 50%, and 90%); B, the forest plot for OS in OAM4558g according to different IHC intensities and different proportional cutoffs (10%, 50%, and 90%). Kaplan–Meier estimates for PFS in patients with IHC scores bordering the diagnostic cutoff; C, patients defined as MET-positive using a 10% cutoff and MET-negative using a 50% cutoff; D, patients defined as MET-positive using a 50% cutoff and MET-negative using a 90% cutoff.

Figure 3

Evaluation of patient outcomes with O+E based upon MET gene copy number. Kaplan–Meier estimates of OS according to MET FISH positivity (≥5 copies of MET/cell) in the ITT (A; n = 19) and EGFRwt (B; n = 15) populations. Kaplan–Meier estimates of OS in patients with MET-positive and MET FISH-negative (<5 copies of MET/cell) tumors in the ITT (C) and EGFRwt (D) populations.

Figure 4

Evaluation of patient outcomes with O+E based upon tumor mRNA expression. The forest plot showing association of MET, AREG, EREG, EGFR, and HGF mRNA expression as determined by quantitative PCR with OS. High, mRNA levels ≥ median; low, mRNA levels < median.

Figure 5

Evaluation of patient outcomes with O+E based upon plasma HGF levels. Kaplan–Meier estimates of OS in patients with low (