A link between race and breast cancer

Black women more likely to get a more lethal form, study finds.

Posted: July 10, 2007

Terry Buie of West Philadelphia had been getting regular checkups and mammograms when a lump seemed to spring up "almost overnight" under her right arm. Breast cancer was the last thing she worried about - she was only 42 and had no family history of the disease.

But when she went to see oncologist Edith Mitchell at Jefferson's Kimmel Cancer Center, Mitchell wasted no time getting Buie to a surgeon to remove the lump for biopsy. Mitchell had seen too many other black women with fast-growing and drug-resistant tumors, and she didn't want to take any chances.

That was the first critical decision that may have saved Buie's life. The second was the intensive course of chemotherapy that Mitchell prescribed. "It was hard," Buie said, "but it was good."

Now 49, she has been cancer-free for the last six years.

Mitchell's instinct that blacks tend to get more aggressive cancers is now backed by science. After analyzing more than 2,000 breast-cancer patients, she and colleagues at Jefferson found that black women were more likely to suffer a particularly aggressive and drug-resistant type of breast cancer.

These findings were released yesterday and slated for publication in the journal Cancer. Mitchell and colleagues at Jefferson hope to use what they have learned to develop drugs to target the more deadly breast tumors.

Researchers have been confounded by a paradox: Black women are less likely than white women to get breast cancer, and yet they are significantly more likely to die from the disease. Some of this can be attributed to black women's lack of access to good screening. "That gap is being closed," Mitchell said, "but the gap in mortality is still widening."

Mitchell, who went to medical school in the early 1970s, was one of only two African Americans in her class at the Medical College of Virginia. While still in medical school, she joined the Air Force and later became the first female physician to rise to the rank of brigadier general.

She decided to specialize in cancer partly because she found it fascinating to examine tumors under the microscope - something she still does with every case. As she studied slide after slide of tumors, she started to see a pattern connected to the patients' race.

While lack of access to health care and poverty clearly matter, she said, her black patients had what she called more poorly differentiated tumors. In these, the cells have strayed further from their normal roles, growing and spreading more wildly. She said it became apparent to her there was a biological difference. "But we had to prove that."

So she teamed with Jefferson researcher Gloria Morris and dug through records from 2,230 cancer patients treated at the hospital from 1990 to 2002.

From the data, they pulled some interesting patterns. White patients were more likely to have tumors that contain what are called estrogen and progesterone receptors. Such tumors can be fought with drugs such as Tamoxifen, which block these hormones.

The white patients were also more likely to have tumors that showed activity in a growth-related protein called HER2. Such tumors, which account for about 20 percent of all breast cancers, respond to a drug approved in 1998 called Herceptin, which was designed specifically to block the action of HER2.

Tumors that don't show HER2, or the estrogen or progesterone receptors, are called triple negative. They are the hardest to cure because they do not respond to any of the newer, more targeted drugs. These are the types of tumors that disproportionately strike black women.

"The breast-cancer cells have found a way to replicate independent of hormonal stimulation," said co-author Morris. "Our only ammunition for these tumors is chemotherapy."

Beyond that, Mitchell's team found the black women's tumors were more likely to show two indications of aggressive spread and growth. One is a molecular marker called ki-67, and another is higher activity in a tumor-suppressing gene called p53. These markers may lead researchers to new targets for attacking the more aggressive tumors.

This is exactly the kind of tumor that Buie had - which is why Mitchell persuaded her to get high-dose chemotherapy over a short time, even though it would mean more severe nausea and other side effects than a more gradual course.

"Breast cancer discriminates," she said. "Colon cancer discriminates," too, she said, spreading faster in blacks, and further research may reveal why.

Last month, researchers from the University of North Carolina at Chapel Hill found similar results using a slightly different category of cancer called basal. Basal tumors are relatively fast growing and also "triple negative."

Lisa Carey, who headed that study, found the racial difference most striking in younger women. Basal-type breast cancers account for about 15 percent of all breast cancers but about 39 percent among black women under 50.

Carey said genetic differences may play a role in the disparity.

But environmental factors also matter. Previous studies show that women who bear children at younger ages are less likely to get the most common but least deadly type of breast cancer.

Other environmental factors that could influence these race differences include exposure to carcinogens, body mass index, and whether women breast-feed and for how long.

The researchers all emphasize that early detection saves lives and that millions of people lack health insurance and therefore aren't getting regular screening or prompt treatment. But they're optimistic with the pace of new discoveries.

The ultimate goal is to formulate better drugs, Morris said. Today, they don't have much beyond standard chemotherapy to offer women with these "triple negative" tumors, but they're starting to get a handle on how these tumor cells work.

"We're focusing our effort on what's driving the proliferation of these cells," Moris said. And since anyone can get these more deadly types of breast tumors, new weapons to fight them could save lives across the board.


 

Inquirer deputy managing editor Sandra Long writes about her own experiences with breast cancer at


Contact staff writer Faye Flam

at 215-854-4977 or fflam@phillynews.com.

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