A blood test for breast cancer?

Mammography has saved many lives in recent decades by detecting breast cancer before a lump could be felt in the breast. But, within this decade, there may be an even better way -- a blood test.

Such a test could determine whether a woman has cancerous breast cells before the cells form a lump large enough to register on a mammogram. Research teams around the country are working on the technique.

The science underlying this quest is called proteomics, a cutting-edge biotechnology that analyzes blood for signs of cancer.

“Proteomics is trying to recognize protein patterns -- fingerprints in the blood or tissue -- that tell the difference between someone with cancer and someone without cancer,” says Dr. Lori Wilson, a surgical oncology fellow at the John Wayne Cancer Institute. She and other researchers at the Santa Monica facility are among those striving to develop a breast cancer test.

“We know that a normal cell has a unique, identifiable protein signature,” Wilson says. “As it changes to a cancer cell, that signature changes too.”

Early in the development of cancer, normal cellular processes go awry, causing an overproduction of proteins that promote tumor growth. Understanding this process could help researchers develop tactics for interrupting the process -- stopping cancer in its tracks -- or for diagnosing it in its earliest stages.

“This could be particularly important in those kinds of cancers where we don’t have good methods to detect cancer early, such as ovarian cancer and pancreatic cancer,” says Carolyn Bruzdzinski, scientific program director for the American Cancer Society.

The technology that makes proteomics possible is a machine called a mass spectrometer. It analyzes proteins by identifying their molecular weight. Using this technology, researchers at the John Wayne Cancer Institute have developed a blood test that -- so far -- correctly distinguishes between normal blood samples and samples indicating cancer 91% of the time. Other research groups around the country have also devised blood tests with similar accuracy rates; it’s too early to predict whose tests will reach the market first -- and when.

Wilson and her colleagues have run their test on 300 women of all ages and ethnicities, including women who have breast cancer and those who don’t. But they hope to enroll at least 1,000 women in the study to better assess and refine the accuracy of the test. After giving a blood sample for the initial test, the women will be followed for seven to 10 years to determine their cancer incidence.

Much more work must be completed, however, before a breast cancer blood test becomes practical for widespread use.

Such a test could yield false positives -- by detecting suspicious abnormalities that are not really cancer. And when a test indicates pre-cancerous cell changes or very early cancer, it may be difficult for doctors and patients to decide how to proceed, Wilson says.

“We are grappling with that,” she says. “We haven’t come to a clear-cut decision on what should happen next.”

It’s most likely that a blood test to detect cancer would be used initially in conjunction with regular mammography, Wilson says. For example, if a mammogram produced an ambiguous finding, a blood test could be given that could indicate whether a woman should proceed to a biopsy.

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Method may be used to detect other cancers

Efforts to create blood tests using proteomics have already yielded a new way of detecting bladder cancer and could lead to screenings for ovarian, lung and prostate cancers.

The U.S. Food and Drug Administration approved a bladder cancer detection test, called BladderChek, earlier this year -- one of the first commercially available blood tests using proteomics technology.

A blood test for ovarian cancer could reach the market in the next few years. Ovarian cancer usually produces no early symptoms, and the cancer typically isn’t diagnosed until it reaches an advanced stage. A study published last month in Proceedings of the National Academy of Sciences found that the test was 100% accurate.

Proteomics tests for lung and prostate cancer have also showed promising results in early studies. Like ovarian cancer, lung cancer is often diagnosed at a late stage. And current prostate cancer screening techniques suffer from inaccuracies, creating the need for better diagnostic tools, experts say.