Test tells source of mystery cancers-researchers

By Maggie Fox, Health and Science Editor

WASHINGTON (Reuters) - A new test that analyzes genetic material can tell doctors the source of some mysterious cancers and perhaps help provide a short-cut for treating them, Israeli researchers reported on Sunday.

Israel-based Rosetta Genomics said its test, still not perfected, uses microRNAs, a type of genetic material that regulates genes and known to be involved in cancer.

Corporate researchers used the microRNAs to identify tumors that had spread in the body from unknown sources -- a type of cancer known as "cancer of unknown primary" or CUP.

Most cancers are named according to the place they first develop -- such as breast cancer or lung cancer or colon cancer. Even if these cancers spread, or metastasize, to the liver or brain or bones they are still identified by their primary origin.

"But there is a group of patients who have tumors that appear in a metastatic site which, with the best imaging, you can't find a primary tumor," said Dr. Martin Raber of the University of Texas M.D. Anderson Cancer Center in Houston.

"It either acquired the ability to metastasize so early in development that primary didn't develop. Or the primary never existed," added Raber, who specializes in such cancers and who was not involved in the research.

CUP accounts for 2 percent to 5 percent of cancers diagnosed in the United States each year, according to the American Society of Clinical Oncology.

Being able to identify the primary origin of a cancer is key to treating it, said Raber.