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Some Breast Cancers Share Genetic Features With Ovarian Tumors

Findings suggest both cancers could be treated with same drugs (Sept. 23)

A comprehensive analysis of breast cancer shows that one of the most deadly subtypes is genetically more similar to ovarian tumors than to other breast cancers.

The findings, announced on September 23 by Washington University in St. Louis and published online in Nature, suggest that most basal-like breast tumors and ovarian tumors have similar genetic origins and potentially could be treated with the same drugs.

Basal-like tumors account for about 10% of all breast cancers and disproportionately affect younger women and those who are African-American.

“Now, we can investigate which drugs work best for patients based on the genetic profiles of their tumors,” said study co-leader Matthew J. Ellis, MD, PhD. “For basal-like breast tumors, it’s clear they are genetically more similar to ovarian tumors than to other breast cancers. Whether they can be treated the same way is an intriguing possibility that needs to be explored.”

Currently, basal-like breast tumors often are treated like many other breast cancers, using anthracycline-based chemotherapy. But another of Ellis’s studies recently showed that women with basal-like tumors don’t benefit from these drugs, which also have severe side effects. At the very least, he said, the new data indicate that clinical trials should be designed to avoid the use of anthracyclines in basal-like tumors.

As part of the new study, a nationwide consortium of researchers analyzed tumors from 825 women with breast cancer. The scientists used six different technologies to examine subsets of the tumors for defects in DNA, RNA (a close chemical cousin of DNA), and proteins. Approximately 350 tumors were analyzed using all six technologies.

The study confirmed the existence of four main subtypes of breast cancer: luminal A, luminal B, human epidermal growth factor 2 (HER2), and basal-like. The latter group includes most triple-negative breast tumors, so-named because they lack receptors for the hormones estrogen, progesterone, and HER2. These tumors often are aggressive and do not respond to therapies that target hormone receptors or to standard chemotherapies.

Across the four subtypes, mutations in only three genes — TP53, PIK3CA, and GATA3 — occurred in more than 10% of patients’ tumors. But the scientists found unique genetic and molecular signatures within each of the subtypes. Their findings add to the growing body of evidence suggesting that tumors should be cataloged and treated based on the genes that are disrupted rather than on the location of the tumor in the body.

For more information, visit the Washington University in St. Louis Web site.

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