Scientists announced Sunday that they have finished mapping virtually all of the genetic mutations in breast cancer, an effort that could soon change the way patients are treated and help researchers develop better treatments.

“The catalog of human breast cancers is nearly complete,” said study co-leader Matthew Ellis of the Washington University School of Medicine in St. Louis. “It’s the breast cancer equivalent of putting a man or woman on the moon.”

Among the most striking findings: One of the most lethal types of breast cancer is genetically closer to a kind of ovarian cancer than it is to other breast tumors, according to the paper, published online Sunday in the journal Nature.

That discovery could soon produce benefits for breast cancer patients, Ellis said. Women with basal-like breast tumors—also known as triple-negative cancers—likely would do better on a much less toxic chemotherapy regimen, which currently is the standard of care in ovarian cancer.

Such shifts show that doctors are beginning to change how they look at cancers, focusing less on a tumor’s organ of origin and more on the inner workings of its nucleus, down to the molecular level, Ellis said.

“Just because it’s a breast cancer doesn’t mean it’s like every other breast cancer,” said Brad Ozenberger, who oversees the research project, called the Cancer Genome Atlas, at the National Institutes of Health.

The genome atlas could give drug companies ideas for new drugs that target key genetic mutations in cancer, Ozenberger said. In addition, the catalog of genetic mistakes can also help scientists better understand how cancers develop and spread, Ozenberger said.

For example, they might find that a newly discovered gene is involved in the immune system—providing a clue to how cancer eludes the body’s normal defenses. Already, the program has given researchers clues that ovarian and triple-negative breast tumors could be vulnerable to drugs that block new blood vessel growth, which aim to starve tumors.

Triple-negative tumors account for about 10%-15% of all breast cancers and are more common among younger women and African Americans.

Today, women with triple-negative tumors are treated like many other breast cancer patients, getting drugs called anthracyclines that can damage the heart and cause leukemia or a type of pre-leukemia, called myelodysplastic syndrome, or MDS.

Ellis’ recent research, however, suggests anthracyclines don’t help women with triple-negative tumors.

One of the best-known breast cancer genes, BRCA1, dramatically increases the risk both of ovarian cancer and triple-negative breast tumors.

###

By Liz Szabo
USA TODAY