Blood tests that can diagnose breast cancer are no longer a pie-in-the-sky idea.
Scientists say in coming years, these tests, so-called liquid biopsies, could reveal whose breast cancer has been cured and whose is likely to return. Eventually, the tests could change the way most cancer is diagnosed and treated.
The possibility emerged when an ultra-specific blood test was approved by the U.S. Food and Drug Administration this year to detect gene mutations in people with the most common type of lung cancer, allowing those with the mutation to be treated with a life-sustaining drug.
"Application of this technology is so wonderful," said Dr. Pasi Janne, a spokesman for the American Association for Cancer Research who has been researching such tests' uses for lung cancer patients. "Simply being able to examine blood to see what's happening and use that to guide therapy is great."
Liquid biopsies look for specific gene mutations from molecules shed into blood. Ideally, results would come faster and more easily than those from traditional tissue biopsies, and they would direct treatments, show how therapies are working, identify cancer likely to recur and someday even find cancer during a routine physical.
Scientists say more of these types of tests are years off, if they ever are developed. But hundreds of trials have launched to investigate liquid biopsies use for a range of cancers, according to a database maintained by the National Institutes of Health.
Among the largest may be one led by Johns Hopkins' Sidney Kimmel Comprehensive Cancer Center that includes 14 institutions. It is seeking to determine if some breast cancer patients are cured after a round of chemotherapy. This would spare them from surgery and radiation and the associated time, discomfort and expense.
Doctors typically give patients all three therapies because they don't know whose cancer will recur.
"We have to prove our marker is that good to deny life-saving treatment," said Dr. Ben Ho Park, a Hopkins associate professor of oncology helping lead the test. "The test will hopefully allow us to say, if you got chemo and you have clear blood, you're done. You're cured."
The study involves women with two types of breast cancer that can be aggressive, triple negative and HER2-positive, and that have spread.
Kelly McNeal, a 36-year-old mother of two, was one of the first volunteers at Hopkins. She said one woman in eight is diagnosed with breast cancer, and she wanted to help them learn what they face, even if it's not a cure.
McNeal hoped researchers would be able to use blood tests to learn who doesn't need extra layers of treatment, but also to help diagnose those with breast cancer in the first place. After her irregular mammogram in August, it took more than a week for her to schedule a traditional biopsy, in which a piece of breast tissue is removed and examined under a microscope, and learn the results.
"I had to wait over Labor Day weekend, and my whole weekend it's all I focused on," said McNeal, a pharmacy technician from Hanover, Pa., who will soon begin chemotherapy for her triple-negative breast cancer at Greater Baltimore Medical Center.
"Once you know, you can put your mind around it and say, 'I've got this, I can take steps, I'm going to fight,'" she said.
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Scientists say combining a blood test with a mammogram to diagnose cancer may be possible. Detecting any kind of cancer in a routine physical would be more problematic.
Scientists consider early detection to be the holy grail, said Steven A. Soper, a professor of biomedical engineering and chemistry at the University of North Carolina, Chapel Hill and a founder of BioFluidica, a firm developing technologies to isolate genetic markers in blood.
Soper, Park and Janne, a senior physician at the Dana-Farber Cancer Institute in Boston, all warned of big hurdles.
Not all cancers have readily identifiable markers, and spotting those that do exist in large volumes of blood is a challenge — though one that has been overcome in the lung cancer test, for example. Tests in the works now focus on more advanced cancer because there are more genetic mutations to find.
If tests can be developed, Soper said, some would be practical, such as with breast or colon cancer. Those with specific markers in their blood would be sent for follow-up. Other tests would have even more profound effects, such as in detection of ovarian or pancreatic cancer, which are usually advanced when they are discovered and hard to treat.
"There are over 100 cancer-related diseases and each has challenges and differences, and some might be easier to develop tests for," Sopor said. But he said that the liquid biopsy for lung cancer, a second similar lung cancer test approved last month, and the one in the works for breast cancer show "this is no longer pie-in-the-sky. It's coming into practice."