Test predicts who will benefit from Iressa
Study of gene mutation on the tumor cells can predict response to Iressa as per research findings from Dr. Fred Hirsch and colleagues of the University of Colorado Cancer Center. A gene test that checks for gene mutation in non-small cell lung cancer (NSCLC) can help predict which patients will be helped Iressa.
These findings are published in the Journal of the National Cancer Institute, could help oncologists to pick out patients who should be treated with Iressa, which has remarkable effects in a small percentage of patients. Iressa may not be very effective in the general population of lung cancer patients, but if only patients with this genetic mutation are chosen for treatment with Iressa the results are promising.
Iressa, otherwise known as gefitinib targets the epidermal growth factor receptor (EGFR) gene which is often mutated in patients with non-small cell lung cancer. Patients with one specific gene mutation in the EGFR gene is now shown to have significant benefit with Iressa.
FDA approved Iressa on May 2, 2003, for the treatment of patients with locally advanced or metastatic non-small cell lung cancer who experienced disease progression on both platinum-based and docetaxel chemotherapies. The approval for Iressa was given based on a 10% response rate under accelerated approval regulations. This approval required subsequent demonstration of clinical benefit in further investigations. As an approval condition, AstraZeneca was committed to conduct a randomized trial examining Iressa effect on survival in this patient population. However a subsequent large randomized clinical trial has shown that Iressa does not prolong survival in general population. The enthusiasm about Iressa has vanished since the publication of this study.
Last year researchers identified a specific mutation in EGFR that predicted who would be helped by Iressa. But it is not a precise test, as some people without the mutation were helped by the drug and some people with the mutation developed resistance.
Dr. Fred Hirsch of the University of Colorado Cancer Center and colleagues looked for an easier and better test. They used one made by Abbott Laboratories Inc. that uses a technology called fluorescence in situ hybridization or FISH to find out how many copies of the gene each patient had.
They found that patients whose tumor cells carried extra copies of the EGFR gene responded better to Iressa. This new study shows that even though Iressa may not be very useful for the general population of non-small cell lung cancer patients, it could still be very useful for a subset of patients with a specific EGFR mutation.
The study examined 102 lung cancer patients with advanced disease, 33 of the 102 patients had several copies of EGFR, and 36 percent of them were helped when treated with Iressa. Just 3 percent of the patients who did not have extra EGFR responded to the drug. These 33 patients also had better survival nearly 19 months compared to seven months. This makes the Abbott assay "an ideal test for selecting candidate NSCLC (non-small cell lung cancer) patients as per the researchers.
Iressa may not be a useful drug for all non-small cell lung cancer patients, but if a subset of patients with specific EGFR mutation is selected for treatment with Iressa, the drug may work very effectively.