The war on cancer is poised to enter a new phase that promises more precise treatments, fewer side effects and, most of all, more survivors.

And none too soon. Although death rates from many cancers have slowly but steadily declined over the decades, experts agree that current treatments are mostly too blunt, too scattershot and too dangerous for the patients they are intended to save.

Today, treating cancer often means an all-out chemical assault on tumors. Doctors bombard patients' bodies with drugs that aim to destroy cancer cells. But like shelling an entire city to wipe out a few rebels, the strategy leaves civilian casualties in its wake: Standard cancer treatments destroy healthy cells alongside diseased ones, taking a toll on a patient's body and strength.

Now, however, the battle tactics are shifting. Researchers have learned how to gather intelligence on a cancer's traits, turn off the tumor's defenses and precisely target only the cells that are causing disease.

"We have the confluence of all these advances coming together at once," says Dr. Ronald DePinho, president of the University of Texas MD Anderson Cancer Center in Houston. "I'm not saying we can cure cancer within 10 years. But we've been handed a complete toolbox. Within this decade, there's no question that we're going to accelerate the decline in mortality due to cancer."

DePinho says the recent revolution in genetics has reignited the world of cancer research. Scientists can sequence all the genes in a cancer cell faster than ever before, compare the cancer genes with those in the rest of the body and even turn genes on and off.

Using these technologies, researchers have discovered that similar-looking cancers can have very different genetic makeups. Understanding the world of mutations can help doctors predict how quickly cancer will grow and which drugs will kill it.

"Oncology as a discipline has always divided itself around body sites," says geneticist Elaine Mardis of Washington University School of Medicine in St. Louis. "There are people who focus on lung cancer and people who focus on breast cancer and people who focus on pancreatic cancer." But the field has realized that cancers are defined as much by their genetic mutations as by location, she says.

When new cancer drugs are in clinical trials, it's already standard practice to see whether the patients who respond have any telltale genetic markers. And in some, cases, such genetic signatures have been found.

Last year, the Food and Drug Administration approved vemurafenib, a melanoma drug that works only in patients with a particular mutation in a gene called BRAF. The drug has no effect in patients without the mutation, so a genetic test is required before a doctor can prescribe it.

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Genetics to determine cancer treatments

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