Doctors have developed a new test to measure cancer cells that break off from lung tumors and travel through the blood.
The technology could one day help physicians to better tailor cancer treatments and monitor tumors in "real time," says Daniel Haber, director of the cancer center at Massachusetts General Hospital and author of a pilot study published online in today's New England Journal of Medicine.
As tumors grow, a handful of cancer cells may peel away and slip into the blood, Haber says. Although few in number -- about one cancer cell for every 1billion blood cells -- these cells can be deadly if they settle in other parts of the body and form new tumors, a process called metastasis. Until now, doctors have never been able to easily analyze them.
The test developed at Massachusetts General uses a silicon chip about the size of a business card, Haber says. The chips are covered with 80,000 tiny pillars that are coated with antibodies, which are designed to stick to cancer cells but allow blood cells to flow past.
Doctors hope to use the test to measure the number of circulating cancer cells, which could tell them if a tumor is growing, shrinking or staying the same, Haber says. Today, doctors measure tumor growth by performing computed tomography, or CT scans, every six to eight weeks. Because blood tests are easier to perform, doctors might be able to measure circulating cells as often as every week or two, allowing them to monitor tumors much more closely, he says. Unlike CT scans, a blood test doesn't expose patients to radiation.
The tests also can identify particular genetic mutations, such as the ones that allow certain lung cancer patients to respond well to the drug Tarceva, a new type of "targeted therapy" that causes fewer side effects, the study shows.
That could give doctors a safe and non-invasive way to predict which patients should get the drug, says Roy Herbst, chief of thoracic oncology at Houston's M.D. Anderson Cancer Center, who was not involved in the study.
Today, doctors often don't know which patients will respond to Tarceva, because they don't have any samples of the patient's tumor to test for genetic mutations. Until now, the only way to get such tissue is through invasive procedures such as needle biopsies, which carry the risk of bleeding or of even collapsing the lung.
Massachusetts General holds a patent on the test. Two of the study's co-authors, Mehmet Toner and Ronald Tompkins, are co-inventors of the test, which has been licensed to CellPoint Diagnostics. Haber says he doesn't yet know the test's cost.
Copyright 2007 USA TODAY, a division of Gannett Co. Inc.
