Breakthrough cancer drug said to have limited impact

Doctors in New York find Iressa `targeted therapy' helps only a few patients

March 16, 2004|By Delthia Ricks | Delthia Ricks,NEWSDAY

Only a minority of patients treated with a breakthrough lung-cancer drug appear to benefit, a discovery that is sending researchers back to the drawing board, doctors in Manhattan said yesterday.

Before federal approval of Iressa last year, patients had clamored for the drug and legions of patient advocates lobbied and met with congressional leaders, demanding approval of the drug.

Iressa is one of a burgeoning class of cancer drugs known as "targeted therapy."

Unlike conventional chemotherapy, targeted medications home in on specific cellular receptors, sites that stud the surface of cancer cells. In theory, once the drug latches onto a receptor, it is capable of shutting down tumor growth and proliferation.

Herceptin, used to treat about one-third of women with breast cancer, is a member of this class; so is Gleevec, prescribed to treat a rare form of leukemia and intestinal cancer.

But while Iressa remains an excellent choice, it apparently is an option for only a few, researchers said yesterday.

"We really need to learn more at this point," Dr. Vincent Miller, a medical oncologist at Memorial Sloan-Kettering Cancer Center in Manhattan and the study's chief investigator, said yesterday. He and his team provide the first report card on Iressa in an analysis appearing in the Journal of Clinical Oncology.

The study analyzes data from three other research projects to draw new conclusions about the drug.

Miller said his review of Iressa was inspired by observations showing "a wide range of patient sensitivity and benefit during our trials and we wanted to understand why."

The study found that patients who benefit most generally have a rare form of lung cancer called bronchioalveolar carcinoma, a type of small-cell lung cancer usually not associated with smoking. That discovery might help lead to the development of a test that can be performed at the time of diagnosis to reveal who will benefit most from therapy.

In their research, Miller and his team found that among 139 patients who had taken Iressa, 15 percent had experienced partial responses to the drug when their progress was viewed by way of X-rays.

Dr. David Carbone, who was not associated with Miller's research, said the study provides new insights into the use of so-called targeted therapy in lung cancer patients.

Carbone, a medical oncologist and cancer researcher at Vanderbilt University in Tennessee, has embarked on a project to develop a screening test that would reveal who would benefit most from treatment with Iressa. The test is based on the study of proteomics, an approach that would reveal specific molecular "patterns."

"I think we'll have in the next couple of years patterns that are strong enough to test," Carbone said. "But it will probably take another three to five years before we make something that is generally available."

Miller also found that even though Iressa was designed to disable the epithelial growth-factor receptor on lung cancer cells, the study found that the drug wasn't most active on that site. It is not clear through which pathways in the cell the drug is most effective.

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