A comprehensive study has categorized breast cancer into four types, already leading to new ideas on how to treat the different strains.
Published online in the journal Nature, the study is part of the Cancer Genome Atlas, a federal project that includes similar studies of lung and colon cancer.
A consortium of researchers from across the country analyzed tumors from 825 patients, using six different technologies to examine subsets of the tumors for various defects.
"We're one giant step closer to understanding the genetic origins of the four major subtypes of breast cancer," says Matthew J. Ellis, one of the study authors who treats breast cancer patients at the Siteman Cancer Center at Barnes-Jewish Hospital and Washington University in St Louis. "This is the road map for how we might cure breast cancer in the future," he told the New York Times.
One key finding, for example, shows that one of the subtypes is genetically more similar to ovarian tumors than to other breast cancer tumors. Patients with that specific mutation, categorized as basal-like, may benefit from the same type of chemotherapy used to treat ovarian cancer, the researchers said.
The four main subtypes confirmed by the study are luminal A, luminal B, HER2-enriched and basal-like.
Researchers noted that cancer patients with luminal A had much better prognoses than those with luminal B, which could help doctors understand when to treat patients more aggressively. And researchers are planning a new clinical trial based on the findings for HER2 patients, who often — but not always — respond well to a drug called Herceptin, allowing a more targeted group to get the drug (and others, who may not respond to it, to avoid it).
"Now, we're much closer to understanding the true origins of the different types of breast cancer," Ellis says. "With this information, physicians and scientists can look at their own samples to correlate patients' tumor profiles with treatment response and overall outcomes. That's the challenge for the future — translating a patient's genetic profile into new treatment strategies."