Device Can Detect Rare Tumor Cells

CTCs are viable cells from solid tumors carried in the bloodstream at a level of one in a billion cells. Because of their rarity and fragility, it has not been possible to get information from CTCs that could help clinical decision-making, but the new device – called the “CTC-chip,”– has the potential to be a useful tool for monitoring and guiding cancer treatment.

“This use of nanofluidics to find such rare cells is revolutionary, the first application of this technology to a broad, clinically important problem,” says Daniel Haber, MD, director of the Massachusetts General Hospital (MGH) Cancer.

Microchip-based technologies have the ability to accurately sense and sort specific types of cells, but have only been used with microliter-sized fluid samples. Since CTCs are so rare, detecting them in useful quantities requires analyzing samples that are 1,000 to 10,000 times larger.

The device the researchers developed utilizes a business-card-sized silicon chip, covered with almost 80,000 microscopic posts coated with an antibody to a protein expressed on most solid tumors. The researchers also needed to calculate the correct speed and force with which the blood sample should pass through the chip to allow CTCs to adhere to the microposts.

Several tests utilizing cells from various types of tumors verified that CTCs were captured by posts covered with the antibody ‘glue.’ Even tumor cells expressing low levels of the target protein and samples containing especially low levels of CTCs were successfully analyzed by the CTC-chip.

The researchers then tested the CTC-chip against blood samples from 68 patients with five different types of tumors – lung, prostate, breast, pancreatic and colorectal. A total of 116 samples were tested, and CTCs were identified in all but one sample, giving the test a sensitivity rating of 99 percent. No CTCs were found in samples from cancer-free control volunteers. To evaluate the device’s ability to monitor response to treatment, blood samples were taken from nine cancer patients during their treatment for lung, colorectal, pancreatic or esophageal tumors. Changes in levels of CTCs accurately reflected changes in tumor size as measured by standard CT scans.; Source: Massachusetts General Hospital