The ALK gene encodes a receptor tyrosine kinase that is recurrently altered by chromosomal rearrangements in multiple malignancies, and the prevalence of oncogenic ALK fusions in lung adenocarcinoma is approximately 5%. The EML4-ALK fusion is known to be oncogenic. Crizotinib is a tyrosine kinase inhibitor that is FDA approved for treatment of ALK-fusion positive lung non-small lung carcinoma.
Somatic mutations in the tyrosine kinase domain of the epidermal growth factor receptor (EGFR) gene are present in approximately 80% of the lung adenocarcinomas that respond to first and second generation EGFR tyrosine kinase inhibitors (TKIs, eg, gefitinib, erlotinib and afatinib). Two types of mutations account for approximately 80-90% of all EGFR mutations: short in-frame deletions in Exon 19 and a point mutation in exon 21 at codon 858 (L858R). Other less common mutations in exons 18, 20, and 21 are found in 10-20% of EGFR-mutated cases. Exon 20 mutations are more commonly associated with resistance to tyrosine kinase inhibitors (TKIs), but may respond to third generation TKI (eg, osimertinib). This EGFR variant (G796S) lies within the tyrosine kinase domain and has been reported in rare cases of lung adenocarcinomas, squamous cell carcinoma of head and neck and prostate adenocarcinoma. In silico studies suggest G796S mutation may confer resistance to TKIs. However, additional studies are needed to further elucidate the oncogenicity of the mutation and therapeutic implications of this rare variant.
Somatic mutations in the tyrosine kinase domain of the epidermal growth factor receptor (EGFR) gene are present in approximately 80% of the lung adenocarcinomas that respond to first and second generation EGFR inhibitors (eg, gefitinib, erlotinib and afatinib). Two types of mutations account for approximately 80-90% of all EGFR mutations: short in-frame deletions in Exon 19 and a point mutation in exon 21 at codon 858 (L858R). Other less common mutations in exons 18, 20, and 21 are found in 10-20% of EGFR-mutated cases. EGFR exon19 deletions, exon 21 L858R and Exon 18 mutations correlate strongly with sensitivity to specific EGFR inhibitors, and the response rate to therapy with TKIs has been reported to be up to 80% in such cases. The T790M mutation in exon 20 is associated with resistance to some EGFR inhibitors. However, third generation TKI (eg, osimertinib) can specifically target T790M. Compound (dual) mutations in EGFR have been previously reported in lung adenocarcinoma and typically include a strong activating mutation combined with a weaker activating mutation. These cases appear to respond well to the EGFR targeted therapies. Mutations at E709 in exon 18 often occur together with other mutations in EGFR. This particular complex deletion insertion variant results in both the E709V and G719C in the protein, as well as a K713R variant, which also has been reported previously.
PTEN is a tumor suppressor gene, and loss of PTEN results in upregulation of the PI3K/ AKT pathway. Loss of PTEN is most commonly due to promoter hypermethylation, while homozygous deletion and nonsense mutations with loss of heterozygosity (LOH) may also occur. PTEN mutations may occur in multiple exons. Somatic mutations in PTEN have been found in 4--8% of non-small cell carcinomas (NSCLC) including adenocarcinomas and squamous cell carcinomas. In preclinical studies, PTEN loss is associated with decreased sensitivity of EGFR mutant lung tumors to EGFR TKIs. Clinical trials assessing the efficacy of PI3K inhibitors in PTEN loss are being explored. This particular variant is known to be oncogenic. It has also been reported as pathogenic/likely pathogenic germline variant according to ClinVar (https://preview.ncbi.nlm.nih.gov/clinvar/variation/376032/).
This gene encodes the catalytic subunit of DNA polymerase epsilon. The enzyme is involved in DNA repair and chromosomal DNA replication. Mutations in this gene have been associated with colorectal and endometrial cancer. P285R is the most common recurrent mutation of POLE in those types of cancers. Somatic POLE mutation is associated with approximately 3% of sporadic microsatellite-stable (MSS) but hypermutated CRCs.
KRAS is a gene that encodes one of the several proteins in the epidermal growth factor receptor (EGFR) signaling pathway that is important in the development and progression of cancer. KRAS can harbor oncogenic mutations that yield a constitutively active protein. Such mutations are found in approximately 30% to 60% of small intestine adenocarcinomas and are common in other tumor types. The relevant KRAS mutation is in one of five codons (12 13, 61, 117 or 146). KRAS mutations in small intestine tumors are associated with higher pT classification and more frequent pancreatic invasion. The effect of KRAS mutations on drug therapy has not been well established in the literature, however it has been extensively studied in colorectal adenocarcinoma. Mutations in the KRAS gene may indicate poor prognosis and poor drug response with therapies targeted to EGFR in colon cancer, and the absence of a KRAS mutation predicts a greater likelihood of response to EGFR-targeted therapies and improved survival with such treatment. The presence of KRAS mutations in codon 12, 13 or 61 is associated with a high likelihood of resistance to therapies targeting EGFR in colon cancer. In addition, mutations at codons 117 and 146 may also be associated with reduced response to EGFR-targeted therapies in colon cancer. Results should be interpreted in conjunction with other laboratory and clinical findings.
Somatic mutations in the tyrosine kinase domain of the epidermal growth factor receptor (EGFR) gene are present in approximately 80% of the lung adenocarcinomas that respond to first and second generation EGFR inhibitors (eg, gefitinib, erlotinib and afatinib). Two types of mutations account for approximately 80-90% of all EGFR mutations: short in-frame deletions in Exon 19 and a point mutation in exon 21 at codon 858 (L858R). Other less common mutations in exons 18, 20, and 21 are found in 10-20% of EGFR-mutated cases. EGFR Exon 19 deletions, EGFR Exon 21 L858R and EGFR Exon 18 G719 mutations correlate strongly with sensitivity to specific EGFR inhibitors and the response rate to therapy with TKIs has been reported to be up to 80% in such cases. The T790M mutation in exon 20 is associated with resistance to some EGFR inhibitors. However, third generation TKI (eg, osimertinib) can specifically target T790M. EGFR K757M has been reported as a rare variant lung adenocarcinoma, but the significance remains to be elucidated.
Erlotinib Afatinib Gefitinib
Somatic mutations in the tyrosine kinase domain of the epidermal growth factor receptor (EGFR) gene are present in approximately 80% of the lung adenocarcinomas that respond to first and second generation EGFR tyrosine kinase inhibitors (eg, gefitinib, erlotinib and afatinib). Two types of mutations account for approximately 80-90% of all EGFR mutations: short in-frame deletions in Exon 19 and a point mutation in exon 21 at codon 858 (L858R). Other less common mutations in exons 18, 20, and 21 are found in 10-20% of EGFR-mutated cases. EGFR Exon 19 deletions, EGFR Exon 21 L858R and EGFR Exon 18 G719 mutations correlate strongly with sensitivity to specific EGFR inhibitors and the response rate to therapy with TKIs has been reported to be up to 80% in such cases. EGFR S768I (exon 20) occurs in 1–2% of EGFR mutant lung cancers and is often coincident with other EGFR mutations. S768I and V769L have previously been identified in the same NSCLC tumors. There are conflicting data regarding the sensitivity to EGFR-TKIs of tumors harboring S768I and V769L mutations. Correlation with other clinical and laboratory findings is necessary.
KRAS is a gene that encodes one of the several proteins in the epidermal growth factor receptor (EGFR) signaling pathway that is important in the development and progression of cancer. KRAS can harbor oncogenic mutations that yield a constitutively active protein. Such mutations are found in approximately 30% to 50% of metastatic colorectal tumors and are common in other tumor types. Mutations in the KRAS gene may indicate poor prognosis and poor drug response with therapies targeted to EGFR. The absence of a KRAS mutation predicts a greater likelihood of response to EGFR-targeted therapies and improved survival with such treatment. The relevant KRAS mutation is in one of five codons (12 13, 61, 117 or 146). The presence of KRAS mutations in codon 12, 13 or 61 is associated with a high likelihood of resistance to therapies targeting EGFR. However, preclinical studies have shown that G13D mutant cell lines have intermediate sensitivity to cetuximab and panitumumab. Results should be interpreted in conjunction with other laboratory and clinical findings.