ATLANTA — Four years after the government severely restricted its use, the lung cancer drug Iressa may be poised to make a comeback: A study concludes it can slow the deadly disease better than standard chemotherapy in certain patients.

The research released Wednesday is the first to show Iressa can be more effective than chemotherapy as a first-line treatment, and some experts are hopeful it will prompt the Food and Drug Administration to allow wide use of the drug, made by AstraZeneca PLC. Others are doubtful.

Though the study shows an effect on cancer growth over one year, the drug's impact on long-term survival is still in question. Also, the study was done in Asia, and the drug seems to work best with specific patients — Asians, women and non-smokers who carry a specific gene mutation.

"I'd venture to say that additional studies will be requested in the United States population," said Dr. Len Lichtenfeld, the American Cancer Society's deputy chief medical officer.

AstraZeneca, which funded the study, is not planning a new push for expanded FDA approval of the drug, a company spokeswoman said. But the company is continuing to share data about the drug with federal health officials, she added.

Iressa is a daily pill that more precisely targets cancer rather than healthy cells. It's an attractive alternative to standard chemotherapy, which involves trips to a hospital or clinic for infusions of poisonous chemicals that cause nausea and hair loss.

In 2003, the FDA approved Iressa as a last-resort treatment for patients with the most common form of lung cancer, called non-small-cell lung cancer.

The market was significant: Lung cancer kills more Americans than any other kind of tumour, and the Cancer Society estimates it will cause nearly 160,000 US deaths this year. Non-small-cell lung cancer represents 85 percent of lung cancer cases.

But in 2005, the FDA stopped allowing new patients to go on Iressa after early results from a federally sponsored study failed to show it improved lung cancer patients' survival rates.

Another lung cancer pill, Roche Group's Tarceva, acts in a way similar to Iressa and remained on the market as a treatment for patients not helped by chemotherapy. There wasn't widespread outcry at the loss of Iressa because Tarceva remained available, said Dr. Edward Kim, a lung cancer specialist at the University of Texas M.D. Anderson Cancer Center.

Interest in Iressa continued, though, as doctors have become increasingly interested in personalised approaches to cancer treatment.