Liquid biopsy could track cancer progress in real time

Scientists say it may be possible to track the progress of cancer — and cancer treatment — in real time from fragments of tumour DNA that are shed into the bloodstream.

Researchers compared simultaneous blood and tumour samples from a woman with advanced metastatic breast cancer over a three-year period. They found the same pattern of genetic changes in both types of sample as she responded to treatment.

'This definitively shows that we can use blood-based DNA tests to track the progress of cancer in real time,' said study author Professor Carlos Caldas of the Cancer Research UK Cambridge Institute. 'The findings could change the way we monitor patients, and may be especially important for people with cancers that are difficult to reach, as taking a biopsy can sometimes be quite an invasive procedure.'

The researchers were able to detect tiny fragments of DNA from dying tumour cells as they were shed into the bloodstream of the 42-year-old woman. They collected eight surgical and nine plasma samples during the course of the study, which was published in Nature Communications.

The tumour fragments displayed the same genetic changes as the tumours themselves as the woman first received tamoxifen treatment, followed by the cancer drugs trastuzumab and then lapatinib. The researchers say they were able to distinguish between her secondary tumours to see how each was responding to treatment — some tumours regressed with the initial treatment while others progressed.

It is hoped that so-called 'liquid biopsies' could one day replace surgical biopsies for many cancers.

'We were able to use the blood tests to map out the disease as it progressed. We now need to see if this works in more patients and other cancer types, but this is an exciting first step,' said Professor Caldas.