A microchip-based device that detects and analyses tumour cells in the bloodstream proved effective in determining the genetic signature of lung tumours, allowing identification of patients appropriate for targeted treatment in a pilot study in patients with non-small-cell lung cancer (NSCLC).

Researchers at Massachusetts General Hospital used the device, which detects circulating tumour cells (CTCs) - living cells from solid tumours, such as lung cancers, found at extremely low levels in the bloodstream - to analyse blood samples from 27 patients with metastatic NSCLC. They were looking for mutations in a protein, epidermal growth factor receptor (EGFR), which affect the response of lung tumour cells to tyrosine kinase inhibitors (TKIs).

These drugs are effective in NSCLC, but their efficacy is greatly reduced in patients with mutations in the EGFR gene. The research group hoped that molecular characterisation of circulating tumour cells would provide a strategy for noninvasive monitoring of tumour genotypes during treatment, to determine whether patients would still response to treatment with a TKI.

Results showed that the CTC-chip was able to isolate circulating tumour cells from all 27 patients in the study, but not from healthy control subjects. It identified EGFR activating mutations in 92% of patients, and a mutation that commonly confers drug resistance (T790M) in 55% of patients.

When T790M was detected in tumour biopsy specimens before treatment, the presence of the mutation correlated with reduced progression-free survival (an average of 7.7 months, compared to 16.5 months in patients without the mutation, p