Most Breast Tumors Have Unique Genetic 'Fingerprint,' Study Finds

SATURDAY, April 2 (HealthDay News) -- Researchers who sequenced the entire genomes of tumors from 50 breast cancer patients identified more than 1,700 mutations, most of which were unique to individual patients.

The findings help explain why it's difficult to predict breast cancer patient outcomes and to find new treatments, said the researchers at Washington University in St. Louis and the Siteman Cancer Center.

After sequencing the tumor genomes, the researchers compared the sequences to the matched DNA of the same patients' healthy cells, which allowed them to find the mutations. They also sequenced the 10 trillion chemical bases of DNA more than 30 times to ensure the data was accurate.

All the patients in the study had estrogen-receptor-positive breast cancer, in which cancer cells have receptors that bind to estrogen and help the tumors grow. The study will be presented Saturday at the American Association for Cancer Research (AACR) annual meeting in Orlando, Fla.

Some genetic mutations that are rare in breast cancer are common in other cancers and there may be drugs available to treat them, lead investigator Dr. Matthew Ellis, a professor of medicine at Washington University School of Medicine in St. Louis, said in an AACR news release.

However, treatment is only possible when the cancer's genetics are known beforehand. The ideal goal is to be able to design treatments by sequencing the tumor genome when a patient's cancer is first diagnosed, Ellis said.

He and the other researchers found two common mutations previously found in breast cancer patients, as well as three new ones that occured in an average of one in 10 women. However, "to get through this experiment and find only three additional gene mutations at the 10 percent recurrence level was a bit of a shock," he said.

In addition, the researchers found 21 other mutations that appeared at much lower rates in several patients. Even though these mutations were relatively rare, Ellis emphasized the finding's value. "Breast cancer is so common that mutations that recur at a 5 percent frequency level still involve many thousands of women," he said.

"We get good therapeutic ideas from the genomic information," he added. "The near term goal is to use information on whole genome sequencing to guide a personalized approach to the patient's treatment."

Because the study is being presented at a medical meeting, the findings should be considered preliminary until published in a peer-reviewed journal.

More information

The U.S. National Cancer Institute has more about breast cancer.

SOURCE: American Association of Cancer Research, news release, April 2, 2011

Copyright © 2011 HealthDay. All rights reserved.

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Do At-Home Genetic Tests Tell Too Much and Explain Too Little?

Do At-Home Genetic Tests Tell Too Much and Explain Too Little?

Experts say field is in its infancy and consumers should seek professional opinions on results

By Maureen Salamon
HealthDay Reporter

FRIDAY, April 1 (HealthDay News) -- At-home pregnancy tests can tell you unequivocally in minutes whether a baby is on the way and if it is time to call your doctor.

But, at-home genetic tests -- which may offer tantalizing clues about future health risks -- are still in their infancy, and genetic counselors are concerned that the results may puzzle or even panic consumers who don't seek professional guidance.

The explosion of direct-to-consumer genetic tests over the past several years has made it seemingly simple to test for a wide variety of medical scenarios. A swab of the cheek or a vial of blood can discern whether one is a carrier of an inherited disorder such as cystic fibrosis, for instance, or predict the risk for diseases such as breast cancer or Parkinson's. Newer tests purportedly predict how people might respond to a specific drug or medical treatment.

But shelling out several hundred dollars or more for one of these tests -- which are widely available online -- does not equip consumers to understand the findings or their repercussions, genetic counselors say. Because people might base medical decisions on the results, the U.S. Food and Drug Administration decided this month to restrict the tests on a case-by-case basis.

"To me, it's still very much in the recreational realm," said Caroline Lieber, a genetic counselor and director of the graduate program in human genetics at Sarah Lawrence College in Yonkers, N.Y. "The concern I have is the majority of the people feel knowledge is power, whereas most haven't thought through the implications at all."

The U.S. Human Genome Project, begun 21 years ago to map out which genes are responsible for both physical and functional traits, led to unprecedented knowledge about how genes affect people's propensity for dozens of traits and conditions.

SOURCES: Caroline Lieber, M.S., director, Joan H. Marks Graduate Program in Human Genetics, Sarah Lawrence College, Yonkers, N.Y.; Robb Rowley, M.D., internal medicine physician, Amigenics, Las Vegas

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