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Previous findings suggest that metastatic colorectal carcinoma (mCRC) patients with KRAS/NRAS/BRAF/PIK3CA wild-type (quadruple-wt) tumors are highly sensitive to anti-epidermal growth factor receptor (EGFR) monoclonal antibodies (MoAbs). However, additional molecular alterations might be involved in the de novo resistance to these drugs. We performed a comprehensive molecular profiling of 21 quadruple-wt tumors from mCRC patients enrolled in the "Cetuximab After Progression in KRAS wild-type colorectal cancer patients" (CAPRI-GOIM) trial of first line FOLFIRI plus cetuximab. Tumor samples were analyzed with a targeted sequencing panel covering single nucleotide variants (SNVs), insertions/deletions (Indels), copy number variations (CNVs), and gene fusions in 143 cancer-related genes. The analysis revealed in all 21 patients the presence of at least one SNV/Indel and in 10/21 cases (48%) the presence of at least one CNV. Furthermore, 17/21 (81%) patients had co-existing SNVs/Indels in different genes. Quadruple-wt mCRC from patients with the shorter progression free survival (PFS) were enriched with peculiar genetic alterations in KRAS , FBXW7 , MAP2K1 , and NF1 genes as compared with patients with longer PFS. These data suggest that a wide genetic profiling of quadruple-wt mCRC patients might help to identify novel markers of de novo resistance to anti-EGFR MoAbs.

Recent findings suggest that a fraction of EGFR-mutant non-small-cell lung cancers (NSCLC) carry additional driver mutations that could potentially affect the activity of EGFR tyrosine kinase inhibitors (TKIs). We investigated the role of concomitant KRAS, NRAS, BRAF, PIK3CA, MET and ERBB2 mutations (other mutations) on the outcome of 133 EGFR mutant patients, who received first-line therapy with EGFR TKIs between June 2008 and December 2014. Analysis of genomic DNA by Next Generation Sequencing (NGS) revealed the presence of hotspot mutations in genes other than the EGFR, including KRAS, NRAS, BRAF, ERBB2, PIK3CA, or MET, in 29/133 cases (21.8%). A p.T790M mutation was found in 9/133 tumour samples (6.8%). The progression free survival (PFS) of patients without other mutations was 11.3 months vs. 7 months in patients with other mutations (log-rank test univariate: p = 0.047). In a multivariate Cox regression model including the presence of other mutations, age, performance status, smoking status, and the presence of p.T790M mutations, the presence of other mutations was the only factor significantly associated with PFS (Hazard Ratio 1.63, 95% CI 1.04⁻2.58; p = 0.035). In contrast, no correlation was found between TP53 mutations and patients' outcome. These data suggest that a subgroup of EGFR mutant tumours have concomitant driver mutations that might affect the activity of first-line EGFR TKIs.