Iressa (gefitinib)

Iressa® is a targeted therapy that is used to treat some non-small cell lung cancers (NSCLC) that have a certain EGFR (epidermal growth factor receptor) mutation, specifically the exon 19 deletions or exon 21 (L858R) substitution mutation. EGFR mutation is determined by biomarker tests (molecular testing) conducted on a biopsy sample of the tumor. Iressa is an EGFR inhibitor and is also classified as a tyrosine kinase inhibitor. It is designed to block the activating sites (tyrosine kinases) of several proteins within the cancer cell. These proteins can stimulate cancer growth when the tumor has an EGFR mutation. By blocking the action of the proteins, Iressa may shrink the cancer or slow the cancer’s progression.1,2

Iressa is used to treat NSCLC that are positive for EGFR mutation (exon 19 deletions or exon 21 (L858R) substitution) that are metastatic (spread to distant parts of the body) prior to other treatment.2

About EGFR Mutations

An estimated 10% of patients with non-small cell lung cancer (NSCLC) in the United States have a tumor mutation associated with EGFR. EGFR mutations are most often found in tumors in female patients who have never smoked (patients are considered “never smokers” if they have smoked less than 100 cigarettes in their lifetime). The tumors are likely to be adenocarcinoma. However, EGFR mutations are not exclusive to this type of NSCLC or non-smokers – mutations have also been found in smokers and in other tumor types.3,4

Taking Iressa

Iressa is a pill that is taken by mouth once daily. It may be taken with or without food. The dosage of Iressa is determined by several factors, including the patient’s general health and ongoing response to treatment.2

Side Effects of Iressa

Iressa may cause side effects, and in some cases, these side effects can be severe. Any side effects should be reported to a health care professional. Side effects experienced in greater than 30% of patients taking Iressa are diarrhea and skin reactions, such as a rash or acne. Less common side effects experienced in 10-29% of patients receiving Iressa include nausea, vomiting, itching, poor appetite, and eye irritation. Rarely, severe side effects of pneumonia or inflammation of the lung without infection have occurred, potentially accompanied by difficulty breathing with cough or low-grade fever. Patients experiencing sudden shortness of breath or cough, fever, jaundice (yellowing of the skin or eyes), or severe abdominal pain while taking Iressa should seek medical care immediately.1,2


Patients receiving Iressa should talk to their doctor about other medications, herbal remedies, and any supplements they are taking, as well as any other health conditions. Patients should not take aspirin while taking Iressa without discussing with their doctor. Patients should talk to their doctor before receiving immunizations or vaccinations while taking Iressa to make sure they are appropriate. Patients who are pregnant or may become pregnant during treatment should discuss their condition with their doctor prior to starting Iressa, as it may be hazardous to the fetus. It is not known whether Iressa passes into breast milk, and patients should not breastfeed while taking Iressa.2

Written by: Emily Downward | Last reviewed: October 2018.
View References