Biomarkers of benefit from cetuximab-based therapy in metastatic colorectal cancer: interaction of EGFR ligand expression with RAS/RAF, PIK3CA genotypes
1 Department of Medical Oncology, Ioannina University Hospital, Ioannina, Greece
2 Department of Pathology, Aristotle University of Thessaloniki School of Medicine, Thessaloniki, Greece
3 Laboratory of Molecular Oncology, Hellenic Foundation for Cancer Research, Aristotle University of Thessaloniki School of Medicine, Thessaloniki, Greece
4 Department of Oncology, Ziekenhuis Oost-Limburg, Genk, Belgium
5 Health Data Specialists Ltd, Athens, Greece
6 Department of Medical Oncology, “Hippokration” Hospital, Athens, Greece
7 Division of Oncology, Department of Medicine, University Hospital, University of Patras Medical School, Patras, Greece
8 Bank of Cyprus Oncology Center, Nicosia, Cyprus
9 Department of Medical Oncology, “Papageorgiou” Hospital, Aristotle University of Thessaloniki School of Medicine, Thessaloniki, Greece
10 Third Department of Medical Oncology, “Agii Anargiri” Cancer Hospital, Athens, Greece
11 Department of Pathology, Ippokration Hospital, Athens, Greece
12 Department of Pathology, University Hospital, University of Patras Medical School, Patras, Greece
13 Third Department of Medical Oncology, “Hygeia” Hospital, Athens, Greece
14 Second Department of Medical Oncology, “Metropolitan” Hospital, Piraeus, Greece
15 First Department of Medical Oncology, “Metropolitan” Hospital, Piraeus, Greece
16 Department of Pathology, “Papageorgiou” Hospital, Thessaloniki, Greece
17 Oncology Department, General Hospital of Chania, Crete, Greece
18 Oncology Section, Second Department of Internal Medicine, “Hippokration” Hospital, Athens, Greece
BMC Cancer 2013, 13:49 doi:10.1186/1471-2407-13-49Published: 2 February 2013
More than half of patients with KRAS-wild type advanced colorectal cancer (CRC) fail anti-EGFR monoclonal antibodies. We studied EGFR-axis messenger RNA (mRNA) expression and RAS, RAF, PIK3CA mutations in order to identify additional biomarkers of cetuximab efficacy.
Previously genotyped (KRAS, NRAS, BRAF, PIK3CA mutations) formalin-fixed paraffin-embedded tumour biopsies of 226 cetuximab-treated CRC patients (1st to 3rd line therapy) were assessed for mRNA expression of epidermal growth factor receptor (EGFR) and its ligands EGF, Transofrming Growth Factor-a (TGFA), Amphiregulin (AREG) and Epiregulin (EREG) with real time quantitative PCR. Mutations were detected in 72 (31.9%) tumours for KRAS, in 6 (2.65%) for BRAF, in 7 (3.1%) for NRAS and in 37 (16.4%) for PIK3CA.
Only PIK3CA mutations occasionally coexisted with other gene mutations. In univariate analysis, prognostic significance for survival ( from metastases until death) was seen for BRAF mutations (Hazard Ratio HR 8.1, 95% CI 3.4-19), codon 12-only KRAS mutations (HR 1.62, 95% CI 1.1-2.4), high AREG mRNA expression only in KRAS wild type CRC (HR 0.47, 95% CI 0.3-0.7) and high EREG mRNA expression irrespective of KRAS mutation status (HR 0.45, 95% CI 0.28-0.7). EREG tumoural mRNA expression was significantly associated with a 2.26-fold increased likelihood of objective response to cetuximab therapy (RECIST 1.1). In multivariate analysis, favourable predictive factors were high AREG mRNA in KRAS wild type tumours, high EREG mRNA, low Ephrin A2 receptor mRNA. Cetuximab-treated patients with AREG-low KRAS wild type CRC fared very poorly, their survival being similar to KRAS mutant CRC. Patients with KRAS codon 13 or other non-codon 12 mutations had a median survival (30 months, 95% CI 20–35) similar to that of patients with KRAS wild-type (median survival 29 months, 95% CI 25–35), in contrast to patients with KRAS codon 12 mutations who fared worse (median survival 19 months, 95% CI 15–26).
BRAF and codon 12 KRAS mutations predict for adverse outcome of CRC patients receiving cetuximab. AREG mRNA reflects EGFR signalling in KRAS wild type tumours, predicting for cetuximab efficacy when high and failure when low. EREG may have a prognostic role independent of KRAS mutation.