A microfluidic device called the Cluster-Chip, developed by a team of scientists at Massachusetts General Hospital, is the first designed specifically to capture clusters of two or more rare circulating tumor cells (CTCs), rather than single cells. The ability to isolate intact clusters, they say, can enable researchers to investigate their role in the metastatic process. The strategy behind the design of the microchip device is based on the actual physical properties of cell clusters. The plastic chip through which a blood sample is passed consists of rows of triangular microposts arranged in such a way that clusters passing between two posts become trapped on the apex of a third central post and held in place by the balanced flow of fluid on either side.

In testing blood samples from 60 patients with either breast cancer, melanoma or prostate cancer, the Cluster-Clip captured CTC clusters in 30-40% of the samples. Analysis revealed they consisted of cells with significant molecular differences, and were often accompanied by immune cells, which could have important implications with the increased attention to immune-system-based cancer therapies. Also, there were significantly more CTC clusters in the blood than was previously believed.

The scientists say that since they can capture clusters because of their physical properties, this chip is directly applicable to all types of cancer.