What you carry at this position in your DNA and what research says about it.
Somatic Cancer Gene: 8/10 evidence, 10 publications.
You're viewing every possible genotype for this variant.
None of these is your result. Use the genotype toggle to compare them, then sign up and upload your DNA to see which one is yours.
Sample genotype (not yours): C/C
Typical Inherited EGFR Sequence
Your inherited copies of EGFR do not carry the T790M change. T790M is usually ACQUIRED by a tumour during treatment with EGFR inhibitors, as a resistance change, rather than inherited. This result therefore does not describe lung cancer risk, and any tumour's EGFR status is established by testing the tumour itself.
What this genotype means: Typical baseline lung cancer risk; Standard response to first-generation EGFR inhibitors.
Sample genotype (not yours): C/T
Inherited EGFR T790M Reported
A T790M change is reported on one inherited copy of EGFR. T790M is usually acquired by a tumour during EGFR-inhibitor treatment; a rare inherited form has been described in familial lung cancer, but it is uncommon enough that an array result warrants clinical-grade confirmation before it is treated as real.
What this genotype means: Significantly increased risk of lung cancer; Resistance to first-generation EGFR inhibitors; Favorable response to third-generation EGFR inhibitors.
Sample genotype (not yours): T/T
A T790M change is reported on both inherited copies of EGFR. This is exceptionally unusual and on array data is more likely a genotyping artifact than a real inherited finding. It warrants clinical-grade confirmation and does not by itself describe lung cancer risk.
What this genotype means: Highly elevated risk of lung cancer; Resistance to first-generation EGFR inhibitors; Favorable response to third-generation EGFR inhibitors.
Gene function and biological role
Gene Function: The EGFR gene encodes the epidermal growth factor receptor, a cell surface protein that binds to growth factors to initiate cell division and survival signaling pathways. Under normal conditions, this receptor helps regulate epithelial tissue development and repair. However, overactivation or mutations in this gene can lead to uncontrolled cell proliferation, which is a hallmark of cancer. In non-small cell lung cancer, somatic mutations in this gene frequently drive tumor growth. Understanding both inherited and acquired variations in this gene helps guide targeted cancer therapies.
Variant Impact: The rs121434569 variant, commonly known as the T790M mutation, represents a cytosine-to-thymine change that replaces the amino acid threonine with methionine at position 790 of the EGFR protein. This specific position lies within the kinase domain, where ATP binds to activate the receptor. The substitution of a bulkier methionine residue increases the receptor's affinity for ATP, which prevents first-generation tyrosine kinase inhibitors from effectively binding and blocking the receptor [1]. While most frequently arising as an acquired somatic mutation during cancer treatment, it can also be inherited as a rare germline variant that significantly increases susceptibility to developing lung cancer [2].
Key Insight: The T790M variant is famous as an acquired resistance mutation in lung tumors, but it can also be inherited as a rare germline variant that predisposes families to lung cancer.
Location: EGFR. Chromosome 7 · 7p11.2 · 55.2 Mb
Estimated prevalence by population
No frequency data available
This variant is not present in the gnomAD database.
Showing effects for C/C genotype
Cancer & Oncology
Lung Cancer
Lung Cancer. Evidence: 8/10. Source: PMID 16258541. Typical Risk.
Showing effects for C/T genotype
Lung Cancer. Evidence: 8/10. Source: PMID 16258541. Increased Risk.
Showing effects for T/T genotype
What this genotype means for the people who carry it
Sample genotype: CC (Homozygous)
Having the typical C/C genotype means the EGFR gene encodes the standard threonine residue at position 790. This structure allows first-generation tyrosine kinase inhibitors like erlotinib and gefitinib to bind effectively to the kinase domain if an activating mutation is present in a tumor [1]. Consequently, patients with this genotype do not carry the inherited resistance factor that limits the efficacy of these targeted therapies [2]. Furthermore, this genotype does not confer the hereditary susceptibility to lung cancer associated with the rare T allele [3]. Standard clinical guidelines and treatment protocols for EGFR-mutated lung cancers are highly effective in individuals with this baseline genetic profile.
Typical baseline lung cancer risk; Standard response to first-generation EGFR inhibitors.
Sample genotype: CT (Heterozygous)
Inheriting the T allele introduces a germline mutation that alters the EGFR receptor's ATP-binding pocket, making it a powerful susceptibility factor for non-small cell lung cancer [1]. Clinical studies show that over half of individuals carrying this germline variant eventually develop lung cancer, often by age 60 [2]. If lung cancer does develop, the presence of this mutation blocks the effectiveness of first-generation inhibitors like erlotinib and gefitinib by increasing the receptor's affinity for ATP [3]. However, third-generation inhibitors such as osimertinib are specifically designed to overcome this resistance mechanism and show high efficacy [4]. Close clinical monitoring and early screening are often discussed for carriers of this rare variant to detect any lung nodules early.
Significantly increased risk of lung cancer; Resistance to first-generation EGFR inhibitors; Favorable response to third-generation EGFR inhibitors.
Sample genotype: TT (Homozygous)
Possessing two copies of the T allele is exceptionally rare in the general population, as the variant allele frequency is less than 0.01% globally. This genotype represents a homozygous state for the T790M mutation, which significantly enhances EGFR kinase activity and drives hereditary lung cancer susceptibility [1]. The altered receptor structure prevents first-generation tyrosine kinase inhibitors like gefitinib and erlotinib from binding, leading to poor treatment response and decreased survival if these drugs are used [2]. Fortunately, third-generation inhibitors like osimertinib are highly effective because they covalently bind to the mutated receptor, bypassing the ATP-affinity barrier [3].
Highly elevated risk of lung cancer; Resistance to first-generation EGFR inhibitors; Favorable response to third-generation EGFR inhibitors.
Variants with shared genetic architecture
rs121434568 · EGFR Gene · Chr 7 · EGFR Inhibitor Response
rs2227983 · EGFR Gene · Chr 7 · EGFR Therapy Response
rs2293347 · EGFR Gene · Chr 7 · Gefitinib Response
The T790M mutation in EGFR kinase causes drug resistance by increasing the affinity for ATP.
EGFR-T790M is a rare lung cancer susceptibility allele with enhanced kinase activity.
Content updated August 2026.
ReadYourDNA provides educational interpretation of DNA data you already have. It is not diagnostic, not a substitute for professional medical advice, diagnosis, or treatment, and is not intended to diagnose, treat, cure, or prevent any disease. Talk to a clinician before acting on any result.
Raw DNA Data Reports for 23andMe & AncestryDNA · About ReadYourDNA · FAQ · Methodology & Science · Pricing · Support and complaints · Legal & Contact · Health Traits · Pharmacogenomics · Carrier Status · Variant Explorer · The Human Karyotype · Privacy Policy · Terms of Service · Accessibility · Consumer Health Data Privacy · Your Privacy Choices · Editorial Standards · Your Data, Checkable · Sample Report · ReadYourDNA and Promethease compared · What is inside a 23andMe raw data file · What is inside an AncestryDNA raw data file · What a chatbot can and cannot do with your raw DNA file · Where a raw DNA file can still be uploaded in 2026
Written, maintained and operated by Martin Pechhacker, sole proprietor, Vienna, Austria. Trade register GISA 40064420. support@readyourdna.com