Barbara Bradfield has lived to see dramatic changes in breast cancer.

When she was diagnosed in 1989, Bradfield's tumor — which produced an overabundance of a protein called HER2 — was considered especially deadly. Today, women with tumors like hers have some of the best survival rates in breast cancer.

Experts say the drug that has kept Bradfield healthy for so long, Herceptin, has changed the nature of breast cancer and helped doctors better understand what causes the disease.

In the 10 years since it was approved, doctors say Herceptin also has encouraged the development of a growing arsenal of new therapies that target cancer cells but spare patients from many of the grueling side effects of traditional chemotherapy. Bradfield, who received chemo before and during her Herceptin therapy, developed permanent hearing loss and numbness in her fingers because of those older drugs.

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Yet critics say researchers haven't made as much progress as many had hoped and note that high prices threaten to limit access to promising technologies.

For decades, doctors treated breast cancer as if it were one disease, says Bradfield's doctor, Dennis Slamon, who helped develop Herceptin. Today, Slamon says, doctors recognize that breast cancer is actually a group of seven distinct diseases fueled by different processes inside cells.

Herceptin is designed for the 25% of tumors that make too much HER2, says Slamon, director of clinical/translational research at UCLA's Jonsson Cancer Center. Herceptin, a man-made antibody, turns off the signals that fuel these breast tumors.

In the future, Slamon says, doctors will increasingly prescribe drugs that are specially tailored to each of these subtypes. "The old 'one size fits all' approach, which really dominated clinical trials for four decades, that needs to go away," he says.

Works even in early stages

At the time Bradfield was being treated, Slamon had trouble finding support for his research. His struggle will be depicted Saturday in a Lifetime movie, Living Proof (9 p.m. (ET/PT).

Today, few companies are developing conventional chemotherapies, says Brian Druker, head of the cancer institute at Oregon Health & Science University. But companies have at least 200 targeted drugs in their pipelines.

Doctors also have changed the way they use drugs such as Herceptin.

In the beginning, doctors focused on patients such as Bradfield, who had the most advanced disease. Though Herceptin didn't cure most patients, combining it with traditional chemo helped women live a median of 25 months, compared with women who received only chemo, who lived a median of 20 months.

In a 2005 study in The New England Journal of Medicine, researchers showed that Herceptin works even better in women with early tumors, reducing relapses by half.

Louise Cooper, 55, was one of the first to get Herceptin as preventive therapy. Ten years later, she's cancer-free, has climbed the highest mountains on four continents and is training to run a race in Antarctica.

"I feel blessed," Cooper says. "How can you complain when you were supposed to die?"

Now, doctors are testing Herceptin with other targeted therapies, such as Avastin, to see whether the drugs work even better in combination, Slamon says. The Food and Drug Administration also has approved a second-generation drug, called lapatinib or Tykerb, that keeps cancers in check after Herceptin stops working.

There are drawbacks

Yet some say that Herceptin's promise hasn't been realized.

Although Herceptin itself causes no side effects, it's only partly effective when given alone. Combining it with chemo makes Herceptin work better. But that means that women aren't able to escape chemo-related side effects, says Fran Visco, president of the National Breast Cancer Coalition.

Herceptin also amplifies the heart damage caused by certain chemo drugs, Slamon says.

And even with chemo, Herceptin helps only half of women whose tumors overproduce HER2, according to UCLA.

Herceptin also set a new standard in price. It can cost up to $40,000 for a 12-month course, according to manufacturer Genentech. Newer cancer drugs cost even more. Avastin, for examples, sells for $55,000 a year.

Cooper says the total cost for care — including Herceptin — was $350,000. Although her insurance covered almost all of it, many patients struggle to pay for care. "The goal was to save lives and make sure everyone has access to it," Visco says. The prices of new cancer drugs, she says, "are mind-boggling."