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.
"Today we have specific chemotherapies. We have therapies for colon cancer that don't seem to work in other settings," Raber said in a telephone interview. "You can no longer design one regimen that captures all tumors."
One drug cannot even be used to treat all types of breast cancer or lung cancer, although many drugs work for a variety of cancers.
Tracking down the source
Writing in the journal Nature Biotechnology, Nitzan Rosenfeld of Rosetta and colleagues said they used microRNAs as biomarkers to identify where in the body a tumor started.
After examining 400 samples of 22 different tumor tissues and metastases, they identified the source in two-thirds of cases, they reported.
"Rosetta Genomics is currently developing a technology that will be the basis of a CUP diagnostic tests," the company said in a statement. They will submit it for U.S. Food and Drug Administration approval later this year.
"This research demonstrates the tremendous potential of microRNAs as effective biomarkers, and is a significant step towards the development of the first microRNA-based diagnostic tests," said Amir Avniel, president and chief executive officer of Rosetta Genomics.
Raber, who has informally spoken with Rosetta about using the test, said eventually such tests will become more refined.
"At the end of the day as a doctor I don't really care if my unknown primary tumor patient had breast cancer, colon cancer or lung cancer," he said.
"All I really care about is what treatment will my patient respond to. Some day we will have gene panels that predict responsiveness to taxanes or ... Erbitux or responsiveness to Avastin," he added, naming several types of cancer drugs.
Companies are working to develop those tests, too.
