Medical Oncologist
EGFR-mutant lung cancer
Who Is Eligible for — Gefitinib (Iressa)?
Gefitinib is not suitable for all lung cancers. It works only when your tumour carries a specific change in the EGFR gene. A single molecular test on your biopsy tissue answers the eligibility question.
Medically reviewed by Dr. T. Raghavender Reddy, Medical Oncologist, MBBS · DM (Medical Oncology) · MD (Radiation Oncology) · Last reviewed August 2026
- Mutation testing decides it — Your EGFR result, not your cancer stage or smoking history alone, determines whether gefitinib is right for you.
- Two mutations cover most cases — An exon 19 deletion or an L858R change in exon 21 are the most common sensitising mutations that indicate gefitinib.
- Wild-type means a different treatment — If no EGFR mutation is found, gefitinib is not indicated and your oncologist will recommend a different approach.
- Testing usually uses your existing biopsy — In most cases, molecular testing is done on tissue already collected. A new biopsy is usually only needed if the original sample was too small.
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Gefitinib is for people with non-small cell lung cancer whose tumour carries a sensitising EGFR mutation — most often an exon 19 deletion or an exon 21 L858R change. Without that confirmed mutation, gefitinib is not indicated. EGFR molecular testing on your biopsy tissue is the step that answers whether you qualify.
What do these terms on your test report mean?
- EGFR
- Epidermal growth factor receptor. A protein that normally tells cells when to grow and divide. In some lung cancers, a change in the EGFR gene makes this signal permanently stuck in the on position, driving uncontrolled growth.
- Sensitising mutation
- A specific change in the EGFR gene that makes the cancer cell dependent on the EGFR signal to survive. Gefitinib blocks that signal. Not every EGFR mutation is sensitising — only those proven to respond to the medicine indicate its use.
- Exon 19 deletion
- The most common sensitising EGFR mutation. A short section of genetic code is missing from exon 19 of the gene. Tumours with this change are among those most consistently associated with a response to EGFR-targeted treatment, according to NCCN and ESMO guidance.
- L858R (exon 21)
- The second most common sensitising mutation. A single letter of genetic code is changed at position 858 of exon 21. Like exon 19 deletions, this mutation is a standard indication for gefitinib as a first-line treatment.
- EGFR wild-type
- The EGFR gene has no mutation. In this situation gefitinib does not work and is not given. Your oncologist will recommend a different treatment pathway suited to your cancer's biology.
- T790M
- A resistance mutation that can develop after a first-generation EGFR inhibitor stops working over time. Gefitinib does not target T790M; a different, later-generation medicine is used when this mutation appears.
Are you likely to be eligible for gefitinib?
- Your cancer is non-small cell lung cancer (NSCLC)Gefitinib is approved for NSCLC, most commonly adenocarcinoma. Confirm the histology with your oncologist using your biopsy report.
- EGFR molecular testing has been done on your tumour sampleTesting is usually performed on biopsy tissue already collected. If it has not been done, ask your oncologist to request it before any treatment decision is made.
- The result shows a sensitising EGFR mutationAn exon 19 deletion or L858R change in exon 21 are the two most common results that indicate gefitinib. Your report will name the specific mutation found.
- You have not already received an EGFR inhibitor that has stopped workingGefitinib is most often given as an initial treatment. If a previous EGFR medicine has already failed, a different approach is usually needed depending on what resistance mutation has developed.
- You are able to take a daily oral tabletGefitinib is taken once a day by mouth. Your oncologist will assess your general fitness and any other conditions before confirming it is suitable.
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What happens if testing shows no sensitising mutation?
If your EGFR result is wild-type — meaning no mutation is found — gefitinib is not recommended and will not be offered. This is not a failing of the test. It means your cancer is driven by a different mechanism and needs a different treatment.
Your oncologist will then look at other molecular markers. These may include ALK rearrangement, ROS1, and PD-L1 expression, depending on your cancer type and stage. Each result points toward a different treatment option.
Molecular testing typically takes one to two weeks from when the laboratory receives your sample. If the original biopsy tissue was insufficient, a repeat tissue biopsy or a liquid biopsy — a blood test that looks for tumour DNA — may be needed before the question can be fully answered.
Which EGFR results indicate gefitinib — and which do not?
| EGFR test result | Type of finding | Is gefitinib indicated? |
|---|---|---|
| Exon 19 deletion | Sensitising mutation | Yes — standard first-line option per NCCN and ESMO |
| Exon 21 L858R | Sensitising mutation | Yes — standard first-line option per NCCN and ESMO |
| T790M | Acquired resistance mutation | No — a later-generation EGFR inhibitor is used instead |
| Exon 20 insertion | Uncommon, generally non-sensitising | Generally no — different targeted medicines apply |
| Wild-type (no mutation found) | No EGFR alteration present | No — a different treatment pathway is recommended |
| Rare sensitising mutations (e.g. G719X, L861Q) | Less common sensitising changes | Possibly — discuss with your oncologist; evidence is more limited than for common mutations |
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Drug Deep Dive: Alectinib (Alecensa)
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Drug Deep Dive: Osimertinib (Tagrisso)
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- Diet and Nutrition While on Osimertinib
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- Osimertinib (Tagrisso): The Complete Patient Guide
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Common questions
Frequently asked questions
Does smoking history affect whether I can take gefitinib?
Your smoking history does not decide eligibility. EGFR sensitising mutations are more commonly found in people who have never smoked, but they occur in people who smoke or who have smoked as well. What determines eligibility is the molecular test result, not your smoking status. If EGFR testing has not been ordered, ask your oncologist for it regardless of your smoking history.
What is the difference between gefitinib and osimertinib?
Both target EGFR, but they are different generations of the medicine. Gefitinib is a first-generation EGFR inhibitor approved for tumours with sensitising mutations such as exon 19 deletions and L858R. Osimertinib is a third-generation inhibitor that also covers the T790M resistance mutation, which sometimes develops after first-generation treatment stops working. Your oncologist will recommend which is appropriate based on your mutation profile, your stage, and current evidence from bodies including NCCN and ESMO.
Can I be retested if my first EGFR result was inconclusive?
Yes. If the biopsy sample was too small or of poor quality, a repeat tissue biopsy or a liquid biopsy can often give a clearer result. A liquid biopsy analyses circulating tumour DNA from a blood sample and does not require another biopsy procedure, though its sensitivity is somewhat lower than direct tissue testing. Tell your oncologist if your result was inconclusive — it is a reason to retest, not a reason to begin treatment without a clear answer.
Does the stage of my cancer affect eligibility for gefitinib?
Stage matters, but it is a separate question from mutation status. Gefitinib is most commonly used in advanced or metastatic NSCLC with a confirmed sensitising EGFR mutation. It is also approved in some settings as treatment after surgery for earlier-stage EGFR-mutant disease. Whether it applies to your stage is a question your oncologist can answer directly, alongside your mutation result — both pieces of information are needed to make the decision.
What if a biopsy is not possible?
If a tissue biopsy cannot be done safely — because of the tumour's location, your fitness, or another reason — a liquid biopsy may be used instead. This tests a blood sample for EGFR mutations carried in tumour DNA. Your oncologist will explain the limitations of this approach and whether the result is sufficient to guide treatment. Some situations may also allow testing on a previous archived biopsy if one exists.
If gefitinib stops working, are there other options?
Yes. When gefitinib stops controlling the cancer, your oncologist will usually request repeat molecular testing to find out why. The most common reason is a new T790M resistance mutation, which can be targeted by a different medicine. Other resistance mechanisms are also possible, and testing guides what comes next. Progression on gefitinib is a decision point in your treatment plan, not the end of options, and your team should explain clearly what the next step is and why.