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Nation

Doctors seek way to exploit cancer flaw

NEW YORK — For more than a century, researchers were puzzled by the uncanny ability of cancer cells to evade the immune system.

They knew cancer cells were grotesquely abnormal and should be killed by white blood cells. In the laboratory, in petri dishes, white blood cells could go on the attack against cancer cells. Why, then, could cancers survive in the body?

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The answer, when it finally came in recent years, arrived with a bonus: a way to thwart a cancer’s strategy. Researchers discovered that cancers wrap themselves in an invisible protective shield. And they learned that they could break into that shield with the right drugs.

When the immune system is free to attack, cancers can shrink and stop growing or even disappear in lucky patients with the best responses. It may not matter which type of cancer a person has. What matters is letting the immune system do its job.

So far, the drugs have been tested and found to help patients with melanoma and kidney and lung cancer. In preliminary studies, they also appear to be effective in breast cancer, ovarian cancer, and cancers of the colon, stomach, head, and neck, but not the prostate.

It is still early, and questions remain. Why do only some patients respond to the new immunotherapies? Can these responses be predicted? Still, researchers think it may be the start of a new era in medicine.

This period will be viewed as a moment in medical history when everything changed, said Dr. Drew Pardoll, immuno-therapy research director at Johns Hopkins School of Medicine. Companies say, however, they are only beginning to explore the new immunotherapies.

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