March 28, 2001 (New Orleans) -- A new test, called a 'blood biopsy', takes advantage of the latest technology to find only a few cancer cells in millions of blood cells and examine the cancer cells extremely closely. This test has many potential uses, including helping doctors decide whether additional therapy is needed after surgery for cancer, speeding up the detection of cancer recurrences, and assessing the effectiveness of cancer therapy.
Speaking at a press conference at the annual meeting of the American Association of Cancer Research, lead author of the study, Paul O. P. Ts'o, PhD, said that "the most definitive diagnosis for cancer [requires] cells under the microscope examined by a pathologist. Normally that process, which is called a biopsy, ... is reasonably invasive." But with this new blood biopsy technology, physicians can look for cancer cells from an average blood sample. "If you find cancer cells in your blood, it's a definitive indication that you have cancer, ... and the cancer is out in the circulation already." Ts'o is a professor in the department of biochemistry at the Johns Hopkins School of Hygiene and Public Health. He is also chair and CEO of Cell Works Inc, the company that has developed the blood biopsy technology. Both institutions are in Baltimore.
Ts'o and his colleagues as well as researchers from other institutions are still determining what the most promising uses for this blood biopsy technology are. So far, they have looked at the blood of more than 400 cancer patients, and the test seems to have many potential important applications.
For instance, because cancer spreads through the blood, the test is expected to detect cancer recurrences and spread after a tumor has been removed surgically. In fact, this test is able to find evidence of cancer spread faster than other techniques used today, where you have to wait until the cancer cells have settled in another organ and started to grow before they can be found. As a result, a blood biopsy could be used to determine whether people need follow-up treatment, such as chemotherapy, after surgery to kill residual cancer cells.
This test also is useful to help determine early on, again before the techniques used today, whether a cancer therapy is working.
"Dr. Ts'o's data is very exciting because it has great ramifications for a really big advance in being able to detect early cancer cells in circulating blood," Carol Prives, PhD, said at the press conference. "It also takes advantage of well-known and modern makers for changes in cancer cells. We know, for example, that cancer cells will grow very rapidly but at the same time die very rapidly. He can assess both DNA division [which indicates cell growth] as well as the DNA fragments that occur when the cells start to die. The technology that [Cell Works] has developed is very promising for being able to get a microscopic dissection of circulating cancer cells in patients." Prives, who was not involved in the research, is Da Costa professor of biology in the department of biological sciences at Columbia University in New York.
To perform a blood biopsy, physicians draw a standard blood sample, about 20 mL, from their patients and send the samples to Cell Works for analysis. At Cell Works, the sample is put through a process that separates healthy blood cells from cancer cells. The cancer cells are then examined with an extremely strong microscope called a spectroscopic microscope. It is so sensitive that, according to Ts'o, it can find one cancer cell in only 1-2 mL of blood, which translates to one cancer cell in about 10-12 million white blood cells.
Being able to closely examine cancer cells on their own allows the researchers to ensure that the cells are indeed cancerous, find out what kind of cells they are, determine whether these cells are growing or dying, and find out whether the cancer cells are the type that respond to hormones. This latter information is important for cancers that are influenced by hormones, including breast and prostate cancer.