SAN FRANCISCOGenetic mapping of hundreds of breast cancer tumours confirmed there are four main subtypes and discovered that one closely resembles ovarian cancer, suggesting the two may be attacked with similar therapies.

The study, in which the genomes of 825 breast tumours were sequenced, was the most comprehensive of its type involving the disease. It is part of a U.S. research project into the genetics of 20 types of cancers. Earlier this month, the group, called the Cancer Genome Atlas project, released a similar report on new DNA mutations affecting a type of lung malignancy.

The breast cancer findings, published Sunday in the journal Nature, support the expanding medical view that cancers should be categorized by their genetic origins, rather than where theyre found on the body. The link found between breast and ovarian cancer gives scientists added leverage to compare treatments and outcomes across both tumours.

There are certain mutations you can find across cancers in different organs, said Eric Topol, a professor at the Scripps Research Institute in La Jolla, Calif., who was not involved in the research. This is a real transition point, and we have to move toward more sequencing to give patients the best shot toward curing their cancer.

The personalized medicine approach has fuelled a move among drugmakers to identify treatments targeting genetic mutations, such as Roche Holdings Zelboraf and Pfizers Xalkori.

For years, doctors have classified breast cancers according to measures such as how they invade other tissues, their cellular variability, and their appearance when stained with certain chemicals, said Paul Billings, a geneticist who is medical director Life Technologies Corp., a maker of DNA sequencers in Carlsbad, Calif.

Thats the old world, Billings said. The new world is a diagnostic system that will be based on targetable DNA mutations present in breast cancer.

In the breast cancer study, a computer analysis suggests the form known as basal-like, named for its resemblance to basal skin cells, may be treatable with drugs that either cut off the tumours blood supply or prevent blood vessel growth, or chemotherapy, according to a statement from the National Cancer Institute.

The new research backed up earlier work segmenting breast cancer into four groups according to genetic markers: HER2-enriched, Luminal A, Luminal B and basal-like.

More than 72 gene-based therapies are available already, five times as many as in 2006, according to the Personalized Medicine Coalition, an industry advocacy group based in Washington.

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Genetic study points to new breast cancer treatments

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