Gefitinib (Iressa®)

Gefitinib is a new type of cancer treatment currently being developed. It is a man-made chemical that is being used in research trials to treat some types of cancer. Its brand name is Iressa®.

  • Clinical trials
  • How it works
  • What kinds of cancer is iressa being used to treat?
  • How it is given
  • Possible side effects
  • Additional information
  • References

Clinical trials

When a drug is being developed it has to go through various stages of research, called clinical trials or studies. These are intended to establish a safe dosage and find out what side effects the drug may cause. Trials can also show how effective a drug is, and whether it is better than the existing treatments, or provides extra benefit when given alongside existing treatment.

Some trials have shown that gefitinib can shrink cancer tumours a little in some patients with advanced cancer (cancer which has already spread) who have already received standard treatments for their particular type of cancer. However, the drug had no effect on some patients in the trials. When a drug reduces the size of a tumour the effect may not last and the tumour may increase in size again after a short time. Therefore further trials are being carried out in order to determine exactly how effective it is, the side effects it may produce and what dose is safe to give. The results of several large trials are now being analysed to answer these questions.

At this stage the drug is available only to a small number of people in the UK, usually those taking part in the research trials. In certain circumstances it may also be given to particular patients whose cancer specialist thinks it may help (this is called prescribing on a named patient basis).

Many drugs thought at first to be promising may be found to be less effective than existing treatments, or to have side effects that outweigh any benefits. For this reason, doctors and other medical staff carry out frequent and careful checks on the progress of each patient being treated with a drug such as gefitinib.

Trials are currently being carried out to compare gefitinib with standard cancer treatments and see whether it is less or more effective.

How it works

Gefitinib works by blocking (inhibiting) signals within the cancer cells, which prevents a series of chemical reactions that cause the cell to grow and divide. It is known as a signal transduction inhibitor. This process is described in detail below.

On the surface of many types of cancer cell are structures known as epidermal growth factor receptors (EGFRs). The receptors allow epidermal growth factor (a protein present in the body) to attach to them. When the epidermal growth factor (EGF) attaches to the receptor, it causes an enzyme called tyrosine kinase (TK) to trigger chemical processes inside the cell to make it grow and divide.

Gefitinib attaches itself to the EGF receptor inside the cell and prevents the receptor from being activated. This stops the cells from dividing. Gefitinib therefore has the potential to stop the cancer cells from growing. It works in a different way from both chemotherapy and hormonal therapy.

What kinds of cancer is iressa being used to treat?

Previous trials have shown that in people whose cancer cells have many EGF receptors the cancer may be more likely to develop quickly and also more likely to spread to other parts of the body (metastasise).

EGF receptors are found on many types of cancer cells including non-small cell lung cancer, breast cancer, cancer of the bowel (colon and rectum) and prostate cancer. Theoretically iressa could be used to treat any of these types of cancer, but has so far been shown to be most effective against non-small cell lung cancer.

Current trials will show which other types of cancer it is active against.

How it is given

Iressa is taken as a tablet once a day.

Possible side effects

Each person’s reaction to any drug is unique. Some people have very few side effects while others may experience more. The side effects described in this section will not affect everyone having gefitinib. We have outlined the most common side effects. However, we have not included those that are rare, and therefore unlikely to affect you. If you notice any effects which you think may be due to the drugs, but are not listed here, please let your nurse or doctor know.

Diarrhoea This can usually be easily controlled with medicine but tell your doctor if it is severe or continues. It is important to drink plenty of fluids if you have diarrhoea.

Acne-like rash  Your skin may become dry, sore and itchy. Let your doctor know if you develop this side effect as they can prescribe medicines to help.

Nausea (feeling sick) and vomiting  Let your doctor know if this is a problem as very effective anti-sickness medication can be prescribed.

Tiredness  Some people get very tired while taking gefitinib.

Loss of appetite If this happens it may be helpful to speak to a dietitian at the hospital.

Eye problems  If you notice any change to your vision, pain or redness of your eyes let your doctor know.

Breathing problems  A rare side effect of gefitinib is inflammation of the lungs. If you become breathless or your breathing worsens tell your doctor straight away. Although this is a rare side effect it is potentially very serious and a small number of people have died because of the lung problems they have developed while taking gefitinib. If you are worried about this potential side effect talk to your doctor or nurse.

Additional information

  • Keep the tablets in a safe place where children cannot reach them, as gefitinib could harm them.
  • Gefitinib may interact with grapefruit juice. It is advisable not to drink it during a course of gefitinib.
  • If your doctor decides to stop the treatment, return any remaining tablets to the pharmacist. Do not flush them down the toilet or throw them away.
  • If you are sick just after taking the tablet tell your doctor as you may need to take another one.
  • If you forget to take a tablet you can take it as soon as you remember as long as it is more than 12 hours before your next scheduled dose. If it is less than 12 hours then do not take the missed dose.
  • Gefitinib may interact with other medicines that you are taking. Let your doctor know about any medications you are taking, including any non-prescribed drugs such as complementary therapies or herbs.
  • It is not advisable to become pregnant or father a child while having this treatment as it may harm the developing foetus. It is important to use effective contraception.


This section has been compiled using information from a number of reliable sources including:

  • Oxford Textbook of Oncology (2nd edition). Souhami et al. Oxford University Press, 2002.

For further references, please see the general bibliography.

Gefitinib (Iressa®)

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