Medical Oncologist
Targeted therapy
How Does Gefitinib Work? — The EGFR Inhibitor Explained
Gefitinib targets a faulty protein on the surface of certain lung cancer cells. By blocking that protein, it cuts off the signal that tells the cancer to keep dividing.
Medically reviewed by Dr. Bharati Devi Gorantla, Medical Oncologist, MBBS · MD · DM (Adyar, Chennai) · ECMO · MRCP SCE (UK) · Last reviewed August 2026
- A targeted tablet — Gefitinib is taken once a day by mouth. It targets a specific faulty switch on the cancer cell, rather than circulating through the body the way chemotherapy does.
- Works only with an EGFR mutation — Your oncologist will test your tumour before prescribing it. Without the right mutation, the drug has no specific target to act on.
- Different side effects from chemotherapy — Because it blocks one specific protein, the side effects differ — skin rash and diarrhoea are common; severe hair loss and blood count drops are not typical in the same way.
- Resistance can develop over time — Most tumours eventually find a way around the blockade. Your team will monitor for this and discuss the next step if it happens.
17+
Cancer Specialists
on Panel
on Panel
96.9%
Breast Cancer
Survival Rate*
Survival Rate*
15,000+
Patients
Treated
Treated
4.8★
Google Rating
(800+ reviews)
(800+ reviews)
Gefitinib blocks a faulty EGFR protein on lung cancer cells. EGFR is a switch that tells cells to grow and divide; in some lung cancers, a mutation keeps it permanently on. Gefitinib fits into that switch and turns it off. It is taken as a once-daily tablet and is specifically for cancers with EGFR mutations.
How does gefitinib find and block cancer cells?
The mutation creates a faulty switch
A change in the EGFR gene makes the EGFR protein permanently active — like a light switch stuck in the on position. This keeps telling the cancer cell to divide and grow.
You swallow the tablet once a day
Gefitinib is absorbed through the gut and enters the bloodstream. It can be taken with or without food.
The drug reaches the tumour
Gefitinib travels through the blood to the tumour and passes into the cancer cell.
Gefitinib locks into the EGFR switch
Inside the cell, gefitinib fits into the active part of the EGFR protein. With the binding site occupied, the switch can no longer send the grow signal.
The cancer cell slows or stops dividing
Without the grow signal, the cell divides more slowly. In some patients the tumour shrinks; in others it stops growing.
What do these medical terms mean?
- EGFR (Epidermal Growth Factor Receptor)
- A protein on the surface of some cells, including certain lung cancer cells. It acts as a gateway for signals that tell cells to divide. In some lung cancers, a mutation keeps it switched permanently on.
- Tyrosine kinase
- The working part inside EGFR that carries the grow signal into the cell. Gefitinib blocks this part specifically, which is why it is called a tyrosine kinase inhibitor.
- EGFR mutation
- A change in the DNA that makes EGFR permanently active. The two most common in lung cancer are an exon 19 deletion and an exon 21 change called L858R. Your oncologist will specify which one your tumour carries.
- TKI (Tyrosine Kinase Inhibitor)
- The drug class gefitinib belongs to. TKIs block a specific molecular switch inside the cancer cell, rather than poisoning all rapidly dividing cells the way chemotherapy does.
- First-generation EGFR inhibitor
- Gefitinib and erlotinib are first-generation EGFR inhibitors. Second and third-generation drugs were developed partly to address the resistance that can develop to first-generation treatment.
Meet the Specialists
17+ senior cancer specialists. One panel for your case.
Trained at AIIMS, Tata Memorial, and leading international centres. Combined 150+ years of experience. Every complex case is reviewed by 3+ of them — together.
Medical Oncologist
Dr. C. Raghavendra Reddy
MBBS(Gold Medal), DNB(General Medicine), DM(Medical Oncology)(Gold Medal)
Medical Oncologist
Dr. Bharati Devi Gorantla
MBBS, MD(General Medicine), DM(Medical Oncology)(Adyar,Chennai), ECMO, MRCP SCE(UK)
Medical Oncologist
Dr. Owais Mohammed
MBBS, MD (General Medicine), DrNB (Medical Oncology), ECMO, MRCP SCE (Medical Oncology) (UK)
Medical Oncologist
Medical Oncologist
Surgical Oncologist
Dr. Muralidhar Muddusetty
MBBS (AIIMS), MS (Surgery) (AIIMS), DNB (Surgical Oncology), MRCS (Edinburgh)
Surgical Oncologist
Surgical Oncologist
Surgical Oncologist
Dr. Vinay Mamidala
MBBS, MS(General Surgery), M.Ch(Surgical Oncology), FMAS, FARIS(Ongoing)
Surgical Oncologist
Radiation Oncologist
Radiation Oncologist
Radiation Oncologist
Hematologist
Interventional Radiologist
Dr. Mohammed Imran
Surgical Oncologist
Dr. Vajja Sandeep Kumar
MBBS, MS (General Surgery), DrNB (Surgical Oncology), FALS Oncology
Surgical Oncologist
Want a specific doctor for your case? Mention them when booking.
Book Free ConsultationBook an appointment with our specialist
Share your name and number — we'll call you back within 30 minutes to schedule your consultation.
Get a straight answer from a specialist
45 minutes, your reports reviewed, your questions answered in plain language.
Why do you need an EGFR test before starting gefitinib?
Gefitinib only works where there is an EGFR mutation for it to target. In a tumour without that mutation, the drug has no specific mechanism of action on the cancer cells.
Your oncologist tests a piece of your tumour tissue — usually from the biopsy you have already had — to look for the specific mutations gefitinib is designed for. Results typically take one to two weeks.
If the original sample was too small, a repeat biopsy may be needed. A blood test that looks for tumour DNA — called a liquid biopsy — is sometimes used when tissue is difficult to obtain.
How is gefitinib different from chemotherapy?
Chemotherapy targets all rapidly dividing cells in the body. That is why it affects the hair, gut lining, and bone marrow alongside the cancer.
Gefitinib targets a specific protein that is faulty in your tumour. It does not circulate through the body attacking dividing cells — it blocks one pathway.
The side effects reflect this difference. A skin rash, dry skin, and diarrhoea are common with gefitinib because EGFR is also active in normal skin and gut tissue. Severe hair thinning and significant drops in blood counts are not typical in the same way.
What happens when gefitinib stops working?
Most tumours eventually develop a way to grow despite gefitinib's blockade. NCCN and ESMO describe several resistance mechanisms; the most commonly identified is a second change in the EGFR gene, known as T790M, which alters the shape of the target so gefitinib can no longer fit.
When response is lost, your oncologist will arrange further testing — often a blood test for circulating tumour DNA, or a new biopsy — to identify which mechanism is responsible.
Third-generation EGFR inhibitors work specifically against T790M and other resistance mutations. Being on gefitinib first does not close off those options; it informs which option is most appropriate next.
Explore 75 more Lung Cancer Targeted Medicines topics
Drug Deep Dive: Gefitinib (Iressa)
- Diarrhoea on Gefitinib: Home Management and Warning Signs
- Diet and Nutrition While on Gefitinib
- Fertility, Pregnancy and Contraception on Gefitinib
- Gefitinib (Iressa, Geftinat, Geftib): The Complete Patient Guide
- Gefitinib Myths: 'It's Only for Poor Patients' and Other Half-Truths
- Gefitinib Plus Chemotherapy: Does Adding Chemo Actually Help?
- Gefitinib Price in India: Brand, Generic and Monthly Cost
- Gefitinib Rash: Why It Appears in Week Two and How to Treat It
- Gefitinib Side Effects: The Complete List and Timeline
- Gefitinib Success Rate and Survival: An Honest Look at the Numbers
- Gefitinib and Antacids: The Interaction That Silently Reduces Absorption
- Gefitinib in Early-Stage vs Advanced Lung Cancer: Different Goals
- Gefitinib in Elderly Patients and Those With Other Illnesses
- Gefitinib vs Osimertinib: Making the Decision When Cost Matters
- How Does Gefitinib Work? The First-Generation EGFR Inhibitor Explained
- How Long Does Gefitinib Take to Work?
- How Long Will You Stay on Gefitinib?
- Raised Liver Enzymes on Gefitinib: What Your LFT Report Means
- T790M Testing After Gefitinib Stops Working: The Next Step Explained
- Taking Gefitinib: Food, Timing and What to Do If You Miss a Dose
- Tests and Monitoring While You Are on Gefitinib
- When Gefitinib Stops Working: Resistance and What Comes Next
- Who Is Eligible for Gefitinib? EGFR-Mutant Lung Cancer
- Will Insurance or a Government Scheme Pay for Gefitinib?
- Work, Travel and Daily Life on Gefitinib
Drug Deep Dive: Alectinib (Alecensa)
- Alectinib (Alecensa, Alectinib): The Complete Patient Guide
- Alectinib After Surgery for Early-Stage ALK-Positive Lung Cancer
- Alectinib Myths: Is ALK-Positive Cancer 'Curable'?
- Alectinib Price in India: Brand, Generic and Monthly Cost
- Alectinib Side Effects: The Complete List and Timeline
- Alectinib Success Rate and Survival: An Honest Look at the Numbers
- Alectinib and Brain Metastases: How It Protects the Brain
- Alectinib in Elderly Patients and Those With Other Illnesses
- Alectinib vs Crizotinib vs Lorlatinib: Choosing an ALK Inhibitor
- Diet and Nutrition While on Alectinib
- Do You Need Chemotherapy Alongside Alectinib?
- Drug, Food and Supplement Interactions With Alectinib
- Fertility, Pregnancy and Contraception on Alectinib
- How Does Alectinib Work? The Second-Generation ALK Inhibitor Explained
- How Long Does Alectinib Take to Work?
- How Long Will You Stay on Alectinib?
- Muscle Pain and High CPK on Alectinib: When to Worry
- Severe Sun Sensitivity on Alectinib: Preventing Serious Burns
- Taking Alectinib: Food, Timing and What to Do If You Miss a Dose
- Tests and Monitoring While You Are on Alectinib
- Weight Gain, Constipation and a Slow Pulse on Alectinib
- When Alectinib Stops Working: Resistance and What Comes Next
- Who Is Eligible for Alectinib? ALK-Positive Lung Cancer
- Will Insurance or a Government Scheme Pay for Alectinib?
- Work, Travel and Daily Life on Alectinib
Drug Deep Dive: Osimertinib (Tagrisso)
- Adjuvant Osimertinib After Lung Cancer Surgery: Three Years of Tablets
- Breathlessness or New Cough on Osimertinib: Recognising Lung Injury (ILD)
- Diet and Nutrition While on Osimertinib
- Drug, Food and Supplement Interactions With Osimertinib
- Fertility, Pregnancy and Contraception on Osimertinib
- Heart Rhythm and Ejection Fraction Changes on Osimertinib
- How Does Osimertinib Work? The Third-Generation EGFR Inhibitor Explained
- How Long Does Osimertinib Take to Work?
- How Long Will You Stay on Osimertinib?
- Osimertinib (Tagrisso): The Complete Patient Guide
- Osimertinib Myths: Clear Scans, Stopping Early and Generic Quality
- Osimertinib Price in India: Brand, Generic and Monthly Cost
- Osimertinib Side Effects: The Complete List and Timeline
- Osimertinib Success Rate and Survival: An Honest Look at the Numbers
- Osimertinib With Chemotherapy: Who Actually Benefits From the Combination?
- Osimertinib and Brain Metastases: Why It Works Inside the Brain
- Osimertinib in Elderly Patients and Those With Other Illnesses
- Osimertinib vs Gefitinib and Erlotinib: Is the Costlier Drug Worth It?
- Rash, Dry Skin and Nail Problems on Osimertinib
- Taking Osimertinib: Food, Timing and What to Do If You Miss a Dose
- Tests and Monitoring While You Are on Osimertinib
- When Osimertinib Stops Working: Resistance and What Comes Next
- Who Is Eligible for Osimertinib? EGFR-Mutant Lung Cancer
- Will Insurance or a Government Scheme Pay for Osimertinib?
- Work, Travel and Daily Life on Osimertinib
Next step
Still not sure what applies to you?
Send your reports across and a senior medical oncologist will go through what they mean, what is known, and what the options actually are.
Common questions
Frequently asked questions
How long does gefitinib take to start working?
In patients whose tumours carry the target mutation, a response can begin within the first few weeks. Some people notice a reduction in symptoms such as breathlessness or cough in this time. Whether the tumour itself is responding is assessed by imaging — usually a CT scan — after the first few months of treatment. The timing of your scans will follow a schedule your oncologist sets based on your individual situation.
Why does gefitinib cause a skin rash?
EGFR is active not only in cancer cells but also in the skin. Blocking it affects normal skin renewal and causes an acneiform rash — spots similar in appearance to acne, typically on the face, scalp, and upper chest. It is uncomfortable and can affect confidence, but it is usually manageable. Your team can recommend specific moisturisers and, where needed, topical or oral medicines to control it. Tell your team if the rash is causing significant discomfort — there are options to help.
Can gefitinib be taken with food?
Yes. Gefitinib can be taken with or without food. Taking it at the same time each day is more important than whether you eat alongside it. If you vomit within an hour of taking the tablet, do not take a replacement dose that day — just continue your normal schedule the following day. Always tell your team about any other medicines, supplements, or herbal preparations you are taking, as some can affect how gefitinib is absorbed or processed by the body.
What does it mean if gefitinib stops controlling the cancer?
It usually means the tumour has developed a way around the blockade — a process called acquired resistance. Your oncologist will arrange testing to find out which mechanism is responsible, because that determines what comes next. The most commonly described mechanism is a second mutation in EGFR called T790M, for which specific later-generation drugs are available. Resistance developing does not mean all treatment options are exhausted; it means the next step needs to be identified.
Is gefitinib available in India?
Gefitinib is approved by CDSCO and is available in India. It is dispensed through oncology centres rather than general pharmacies. Cost is a real concern for many families. Assistance programmes from manufacturers, and government cancer-care initiatives, may reduce what you pay out of pocket. What is available varies by state and by treating hospital, so ask the team at your centre specifically what support can be arranged for your situation.
Can gefitinib shrink a lung tumour completely?
In a proportion of patients, gefitinib produces significant tumour shrinkage, and complete disappearance on imaging is possible, though it is not the common outcome. The aim of treatment is to shrink or stabilise the cancer for as long as possible, reducing symptoms and preserving quality of life. What response looks like in your case, and what your own scans show, is best discussed with your oncologist directly — outcomes vary between patients and general comparisons rarely translate to an individual situation.