WASHINGTON (Reuters) - The lung cancer pill Iressa has shown surprising results for patients with advanced disease where it has been at least as effective as a standard chemotherapy treatment, researchers reported on Thursday.

Patients who got the once-a-day pill made by AstraZeneca lived as long as those given the chemotherapy treatment Sanofi-Aventis' Taxotere or docetaxel, the international team of researchers found.

This is second-line treatment, traditionally offered after a course of combined chemotherapies that can last months and is still considered the best approach to lung cancer.

"The study is the first time in lung cancer that an oral biological agent has been tested head-to-head against chemotherapy," Dr. Edward Kim of the University of Texas M.D. Anderson Cancer Center in Houston and colleagues wrote in the Lancet medical journal.

Kim's team tested 1,466 patients in 24 countries who had completed a first course of standard chemotherapy. Half got Iressa as second-line treatment and half got docetaxel. Both sets of patients lived about as long -- eight months on average.

Dr. Michael Cullen of University Hospital Birmingham in Britain, who wrote a commentary on the findings, noted that Iressa is far less toxic than chemotherapy, including Taxotere, and is very convenient to take.

"I think there will be patients for whom it will be favored," he said.

But he said in a telephone interview tests supposed to show who would do better on so-called targeted therapies like Iressa failed to predict who would benefit from them.

Iressa was once viewed as a likely blockbuster for the Anglo-Swedish group which makes it, but its failure in a clinical trial in 2004 dealt a major blow for the product and it is now seen by analysts as a niche medicine.

SIDE EFFECTS

Lung cancer kills 1.2 million people a year and is the top cause of cancer death globally. Many drugs are used to treat it but almost always stop working eventually, in part because most patients are not diagnosed until tumors have spread.

Chemotherapy, infused over a period of several hours, targets rapidly growing cells and thus often has severe side effects such as nausea, diarrhea and hair loss.

Iressa, known generically as gefitinib, is a monoclonal antibody, a genetically engineered immune system molecule, that targets a molecule called epidermal growth factor receptor or EGFR. Tumors use EGFR to grow themselves blood supplies.

Such targeted therapies have far fewer side effects.

AstraZeneca stopped selling Iressa in the United States after tests showed it only helped about 10 percent of patients. But it continued trials, including this one, in part because there was tantalizing evidence that some people -- notably non-smokers, Asians and women -- did better on Iressa.

And companies such as Genzyme Corp. now market tests that show whether cancer patients have the EGFR mutation and others targeted by Iressa and similar drugs such as Genentech's Tarceva.

Cullen noted that only a small proportion of the patients benefited from being given the second-line treatment drugs. but said some lived a long time. He described one of his patients who survived a year on Iressa before dying of a stroke.