The drug also, known as Gefitinib, works as well as chemotherapy as a second-line treatment for lung cancer, according to an international Phase III clinical trial, led by researchers at the University of Texas' M D Anderson Cancer Center.

However, in contrast to earlier Iressa findings, the study reported on Thursday showed that there was no additional survival benefit for patients who expressed an elevated level of the epidermal growth factor receptor (EGFR) mutation.

"A pill, with less side effects, taken once a day, has similar activity to traditional chemotherapy given by vein every three weeks," said lead researcher Dr Edward Kim, an assistant professor at the M D Anderson Cancer Center in Houston. This finding should reassure doctors that they are not compromising effective therapy by using a pill, Kim said.

Iressa is not available in the United States, but a similar drug, Tarceva, is. Iressa was first developed by AstraZeneca, but it failed to meet expectations.

The National Cancer Institute ended clinical trials of the drug in 2005 because it failed to prolong the lives of lung cancer patients.

"Based on our findings, I'm hopeful that Iressa can return as a treatment for lung cancer in the United States, offering this some patients a therapy with far fewer side effects," said Kim.

The study is expected to offer both physicians and patients some confidence in another biological oral therapy, erlotinib, commercially known as Tarceva, that hits similar targets as Iressa.

The Phase III international study enrolled 1,466 lung cancer patients from 149 centers in 24 countries. Of those enrolled, 1,433 were evaluable. All had either locally advanced or metastatic disease and had been previously treated for their cancer.

Patients were randomized to receive either Iressa or Docetaxel every three weeks. The study had two primary survival endpoints: in all treated patients and in those whose tumors had high EGFR gene copy number, explained Kim.

The results showed, median overall survival for those receiving Iressa was 7.6 months and one-year survival was 32 per cent, compared to 8 months and a 34 per cent one-year survival for those taking chemotherapy.

In an assessment of quality of life, Iressa patients experienced far fewer side effects, with the most common being a rash and diarrhea. In contrast, patients taking Docetaxel experienced low blood count, infection, and hair loss.

In the subgroup of 174 patients with a high EGFR gene copy number, median overall survival in the Iressa arm was 8.4 months and one-year survival was 32 per cent, versus 7.5 months overall survival and a one-year survival rate of 35 per cent for those taking chemotherapy.