Elsevier

The Lancet Oncology

Volume 12, Issue 8, August 2011, Pages 795-805
The Lancet Oncology

Articles
Molecular biomarkers in non-small-cell lung cancer: a retrospective analysis of data from the phase 3 FLEX study

https://doi.org/10.1016/S1470-2045(11)70189-9Get rights and content

Summary

Background

Findings from the phase 3 FLEX study showed that the addition of cetuximab to cisplatin and vinorelbine significantly improved overall survival, compared with cisplatin and vinorelbine alone, in the first-line treatment of EGFR-expressing, advanced non-small-cell lung cancer (NSCLC). We investigated whether candidate biomarkers were predictive for the efficacy of chemotherapy plus cetuximab in this setting.

Methods

Genomic DNA extracted from formalin-fixed paraffin-embedded (FFPE) tumour tissue of patients enrolled in the FLEX study was screened for KRAS codon 12 and 13 and EGFR kinase domain mutations with PCR-based assays. In FFPE tissue sections, EGFR copy number was assessed by dual-colour fluorescence in-situ hybridisation and PTEN expression by immunohistochemistry. Treatment outcome was investigated according to biomarker status in all available samples from patients in the intention-to-treat population. The primary endpoint in the FLEX study was overall survival. The FLEX study, which is ongoing but not recruiting participants, is registered with ClinicalTrials.gov, number NCT00148798.

Findings

KRAS mutations were detected in 75 of 395 (19%) tumours and activating EGFR mutations in 64 of 436 (15%). EGFR copy number was scored as increased in 102 of 279 (37%) tumours and PTEN expression as negative in 107 of 303 (35%). Comparisons of treatment outcome between the two groups (chemotherapy plus cetuximab vs chemotherapy alone) according to biomarker status provided no indication that these biomarkers were of predictive value. Activating EGFR mutations were identified as indicators of good prognosis, with patients in both treatment groups whose tumours carried such mutations having improved survival compared with those whose tumours did not (chemotherapy plus cetuximab: median 17·5 months [95% CI 11·7–23·4] vs 8·5 months [7·1–10·8], hazard ratio [HR] 0·52 [0·32–0·84], p=0·0063; chemotherapy alone: 23·8 months [15·2–not reached] vs 10·0 months [8·7–11·0], HR 0·35 [0·21–0·59], p<0·0001). Expression of PTEN seemed to be a potential indicator of good prognosis, with patients whose tumours expressed PTEN having improved survival compared with those whose tumours did not, although this finding was not significant (chemotherapy plus cetuximab: median 11·4 months [8·6–13·6] vs 6·8 months [5·9–12·7], HR 0·80 [0·55–1·16], p=0·24; chemotherapy alone: 11·0 months [9·2–12·6] vs 9·3 months [7·6–11·9], HR 0·77 [0·54–1·10], p=0·16).

Interpretation

The efficacy of chemotherapy plus cetuximab in the first-line treatment of advanced NSCLC seems to be independent of each of the biomarkers assessed.

Funding

Merck KGaA.

Introduction

The pivotal phase 3 First-Line ErbituX in lung cancer (FLEX) study compared cisplatin and vinorelbine plus cetuximab with cisplatin and vinorelbine alone in the first-line treatment of 1125 patients with EGFR-expressing, advanced non-small-cell lung cancer (NSCLC).1 Findings from the study showed that the addition of cetuximab to chemotherapy significantly improved overall survival, the primary endpoint of the trial, compared with chemotherapy alone (median 11·3 months vs 10·1 months; hazard ratio [HR] 0·871 [95% CI 0·762–0·996]; p=0·044). Investigators also recorded a significant improvement in response rate (but not progression-free survival [PFS]). The treatment benefit was detected in a population unselected according to histology.

Specific molecular characteristics of tumours (biomarkers) can be informative in relation to patient outcome and can be described as being of predictive or prognostic use. Predictive biomarkers provide information about the clinical benefit associated with a particular treatment or agent. Randomised clinical studies provide an ideal discovery setting for predictive biomarkers, as exemplified by studies of patients with metastatic colorectal cancer.2, 3, 4, 5, 6 Findings from these studies have clearly shown that the efficacy of the EGFR-targeting monoclonal antibodies cetuximab and panitumumab was limited in this setting to patients with KRAS wild-type tumours. Prognostic markers provide information about patient outcome irrespective of differences in treatment. If patients whose tumours have a particular molecular characteristic have an improved outcome in both the control and experimental groups of a randomised study, that marker is regarded as providing prognostic information for patients receiving the standard therapy. However, randomised controlled studies tend to recruit a defined cohort through extensive eligibility criteria, and the clinical value of a prognostic marker can be defined fully only through wider subsequent assessments.

Because KRAS tumour mutation status was clearly predictive in relation to cetuximab efficacy in metastatic colorectal cancer, and because this gene is mutated in 19% of lung cancers,7 KRAS mutation status was a potential biomarker for patients with NSCLC receiving cetuximab. Other candidate NSCLC tumour biomarkers included increased copy number of the EGFR gene, with such events associated with improved outcome in patients receiving an EGFR tyrosine kinase inhibitor (TKI).8 Investigators of a retrospective analysis of a small group of patients (n=76) with advanced NSCLC receiving chemotherapy plus cetuximab also reported that increased EGFR gene copy number, as determined by fluorescence in-situ hybridisation (FISH), was potentially predictive for improved clinical outcome.9 However, a large randomised phase 3 study did not confirm this finding.10 Additionally, activating mutations of EGFR, occurring predominantly in exons 19 and 21, have been linked to improved outcome in patients with advanced NSCLC receiving EGFR TKI monotherapy or chemotherapy with or without an EGFR TKI, suggesting both predictive and prognostic significance for this biomarker.11, 12, 13, 14, 15, 16, 17

A further candidate biomarker was PTEN, with loss of function of this protein common in several human cancers including NSCLC.18 PTEN is a key negative regulator of the PI3K/AKT cell survival pathway, and expression has been reported as reduced or lost as a result of uncharacterised events in 74% of NSCLCs.19 Such events can have prognostic20 and predictive significance in relation to EGFR-targeting therapy.21

In this study, we investigated in FLEX study patients the predictive and prognostic use of four tumour-associated molecular characteristics—tumour KRAS mutation, increased EGFR copy number, EGFR mutation, and PTEN expression status—linked to the EGFR signalling pathway and previously implicated as providing predictive or prognostic information in NSCLC or other tumour types.22, 23

Section snippets

Study design and participants

The FLEX study is a multinational, open-label, phase 3 trial undertaken at 155 centres in 30 countries. The FLEX study design and eligibility criteria have previously been reported in detail.1 Between October, 2004, and January, 2006, patients with advanced NSCLC whose tumours expressed EGFR, as established by immunohistochemistry, were randomly assigned to receive a maximum of six cycles of cisplatin and vinorelbine chemotherapy with or without cetuximab, administered weekly as a 400 mg/m2

Results

Figure 1 shows the trial profile. Tumour tissue samples were evaluable for biomarker status from four subpopulations of patients enrolled in the FLEX study. The baseline characteristics of patients in each of these biomarker subpopulations were similar between treatment groups and with the treatment groups of the overall FLEX intention-to-treat (ITT) population (table 1).

KRAS mutation status was evaluable in tumour-derived DNA samples from 395 of 1125 (35%) patients of the ITT population.

Discussion

Increased understanding of the molecular pathology of NSCLC will facilitate the future identification of predictive biomarkers and provide key components for the personalisation of therapy, allowing the tailoring of existing and novel treatment agents and regimens to patients who are most likely to benefit. The results of this retrospective analysis in FLEX study patients suggested that KRAS mutational status, EGFR copy number, EGFR mutational status, and PTEN expression status were not

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