Microchip Detects Tumor Cells in Blood

Device, Called the CTC-Chip, May Help the Search for Targeted Treatments

From the WebMD Archives

July 2, 2008 -- An experimental technique for detecting and analyzing tumor cells in the blood has the potential to change the face of cancer treatment, researchers say.

Developed by investigators at Massachusetts General Hospital, the microchip-based device has the ability to isolate and analyze circulating tumor cells (CTC) from the blood of patients with solid tumors.

Circulating tumor cells are both fragile and scarce in the blood, accounting for about one in a billion cells in a typical cancer patient's blood sample. Because they are so hard to find, their clinical usefulness has been minimal.

In the near term, the CTC-chip offers the promise of noninvasive continuous monitoring of patients with solid tumors through simple blood testing, in the same way that leukemia patients are now followed, says Daniel Haber, MD, PhD, who directs the cancer center at Massachusetts General and led the research team.

In the very long term, Haber says the device may one day be used to isolate and study the specific cancer cells involved in metastasis (cancer spread).

"We have never been able to study human cancer cells in the act of metastasis, which is what kills patients with cancer," Haber tells WebMD.

CTC-Chip Identifies Gene Changes

In the new study, published online today in the New England Journal of Medicine, the CTC-chip was able to identify genetic changes in circulating tumor cells from blood samples taken from 27 patients with non-small-cell lung cancer (NSCLC).

The device was able distinguish between patients likely to benefit from targeted treatments and those not likely to benefit.

From blood samples drawn from the study participants, the CTC-chip allowed the identification of a specific genetic mutation associated with response to a group of drugs known as tyrosine kinase inhibitors (TKI).

Twenty-three of the patients in the study had the mutation. The CTC analysis accurately detected the mutation 92% of the time.

The analysis also detected a secondary mutation associated with resistance to treatment in some patients whose tumors initially responded to treatment but then started growing again.

Blood samples were analyzed throughout treatment in four patients with the mutation. The analysis showed that circulating tumor cell levels dropped sharply after TKI treatment began and began rising when tumors began to grow again.

The researchers were surprised to find that the genetic makeup of the tumors changed continuously during treatment.

"Some [solid tumors] are treated for many years, but for many of them we don't really have good ways of monitoring changes in tumors during treatment," he says. "The CTC-chip may allow us to follow these tumors in real time."

Continued

Technological Hurdles Remain

The search for targeted therapies that tailor treatment to an individual patient's tumor offers the promise of revolutionizing the treatment of cancer.

And technologies like the CTC-chip should play a big role in this search, American Cancer Society Chief Medical Officer Otis W. Brawley, MD, tells WebMD.

When they are ready for clinical use, such technologies hold the promise of distinguishing between cancers that need to be treated and those that do not, Brawley says.

"A major problem in oncology is that our definition of cancer was established in the 1840s," he says. "We need a 21st century definition of cancer that looks at the genetics of a tumor to determine its potential to spread and cause death."

Several major hurdles have to be cleared before it becomes clear if the CTC-chip will have a role in the everyday treatment of cancer or even in the search for new treatments, Haber says.

It now takes between eight and 12 hours to analyze a single sample -- a process that involves flowing blood through a silicon wafer the size of a business card and then imaging 80,000 microscopic posts coated with an antibody to a protein expressed on most solid tumors.

Haber predicts that the time it takes to analyze samples can be shortened "within a year or two."

"This is breakthrough technology, but we are still at the very early stages of developing it," he says.

WebMD Health News Reviewed by Louise Chang, MD on July 02, 2008

Sources

SOURCES:

Maheswaran, S. New England Journal of Medicine, July 24, 2008; early online release.

Daniel A. Haber, MD, PhD, director, Cancer Center, Massachusetts General Hospital, Boston.

Otis W. Brawley, MD, chief medical director, American Cancer Society.

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