A new technique to analyse the tumour DNA present in patient’s blood circulations is an effective method to monitor breast cancer progression. The technique has been shown to give a hundred-fold improvement in the detection limit for tumour DNA.

Analysis of the DNA that the tumour sheds into the bloodstream provides a non-invasive means of both monitoring tumour progression and identifying targetable mutations. This can allow personalised treatment for the cancer that will be more effective and reduce the risk of adverse effects. However, the concentration of tumour DNA is often too low to be monitored by previous techniques.

This is particularly true for patients following surgery or chemotherapy. Analysis of tumour DNA post-surgery can provide vital clues about how likely the cancer is to resurface.

Plasma samples were taken from 33 women with varying stages of breast cancer. The technique known as TARDIS, Targeted RNA Directed Sequencing, was used to look for specific mutations associated with the tumours. In all cases, tumour DNA was identified in the patients.

The patients then underwent surgery and chemotherapy. After treatment the concentration of tumour associated DNA was lower in patients who had a complete response to the treatment, compared to patients who still had residual disease.

This demonstrated that TARDIS is a viable and sensitive technique for monitoring disease progression.