Gene testing is becoming a significant tool in standard medical care and perhaps most importantly in the search for the perfect drug to target a articular type of cancer.

The detective work begins under the microscope. Here the scientist searches for clues in the genetic makeup of a patient's cancerous tumor. Inside that tumor could be as many as 13 major cancer genes containing 110 variations.

Doctors hope this information will lead to a drug tailored to that particular type of cancer.

"Every tumor has a genetic flaw which is driving that cancer, and if we can figure out for each individual tumor what that flaw is," Dr. Leif Ellisen said. Dr. Ellisen is a cancer specialist with Massachusetts General Hospital in Boston. "That will allow us to match the tumor to effective drugs,"

Doctors routinely try to match a drug to where the cancer is found in the body.

For patients and doctors, that has often meant painful drugs or treatments that miss the mark.

Massachusetts General is the first medical facility in the United States to conduct routine tumor testing.

Lung cancer patients have been the first to undergo the screening.

Dr. Alice Shaw of Massachusetts General says it is a major step toward customized medical treatment. "We have a much more sophisticated understanding of the genetic changes that occur in cancer. And hand in hand with that knowledge, we also have new and improved targeted drugs," Dr. Shaw said.

Doctors found that genetic abnormalities in a breast cancer tumor, for example, appeared similar to abnormalities in tumors of the lung, and they thought these abnormalities might turn up in other tumors as well.

That research led to tumor screening for all cancer patients who entered Massachusetts General.

Linnea Duff has undergone genetic testing. "I was basically preparing for the end of my life," she said.

Duff was diagnosed with terminal lung cancer. She had endured chemotherapy without success. Then her doctors found a genetic mutation that had only recently been identified. A drug targeted to that specific genetic abnormality was being tested.

She took the drug, and her lung cancer disappeared. "It was really the most unbelievable, amazing thing. It was beyond my wildest dreams," she states.

Some cancer specialists warn patients against placing too much hope in the screening. Cancerous tumors, they say, can sometimes be so full of genetic variations that it is hard to determine whether one test or treatment will mean a cure.

But a few hospitals are following Massachusetts General's lead and are beginning tumor screening of their own cancer patients.

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