What EGFR Mutations in

There are several types of EGFR mutations in lung cancer, and here are some common ones:

Exon 19 Deletions: These are the most common EGFR mutations in lung cancer. They involve the deletion of a small portion of the EGFR gene in exon 19, leading to the production of a truncated EGFR protein that is constitutively active.

L858R Point Mutation: This is another common EGFR mutation, occurring in exon 21 of the EGFR gene. It involves a single nucleotide change that results in the replacement of leucine with arginine at position 858 of the EGFR protein. This mutation also leads to constitutive activation of EGFR.

T790M Point Mutation: The T790M mutation occurs in exon 20 of the EGFR gene and is often acquired as a resistance mechanism to first-generation EGFR tyrosine kinase inhibitors (TKIs) such as gefitinib (Iressa) or erlotinib (Tarceva). It leads to a threonine-to-methionine substitution at position 790 of the EGFR protein, which reduces the binding affinity of TKIs to the EGFR and allows the cancer cells to bypass the inhibition.

Other Exon 20 Insertions: In addition to the T790M mutation, there are other less common exon 20 insertions that can also confer resistance to EGFR TKIs. These insertions typically involve the insertion of one or more amino acids into the EGFR protein, leading to conformational changes that affect TKI binding.

Exon 21 L861Q Point Mutation: This mutation is less common than exon 19 deletions or L858R point mutations, but it can also lead to EGFR activation and lung cancer development. It involves a single nucleotide change that results in the replacement of leucine with glutamine at position 861 of the EGFR protein.

It's important to note that the presence of specific EGFR mutations can have implications for treatment decisions in lung cancer, as targeted therapies known as EGFR TKIs are available to inhibit the activity of mutated EGFR and potentially slow tumor growth. The type of EGFR mutation can also impact the choice of specific TKI and the likelihood of developing resistance to treatment over time.