Metastatic breast cancer (mBC) remains a challenge for both patients and clinicians. Currently, most women with mBC will undergo tumour tissue biopsies to determine diagnosis and management. These biopsies are invasive and may cause significant patient discomfort. Single tissue biopsies are also not able to monitor tumour progression during the course of treatment.
Due to these limitations, other techniques for monitoring changes in a tumour over time are greatly needed. One such method is a “liquid biopsy”, which is a simple blood test that can provide vital clinical information. Many breast cancers shed small amounts of DNA (called circulating DNA or ctDNA) into the bloodstream. These can be detected by the liquid biopsy and used to assist with treatment selection and disease monitoring in real time.
Until now, little was known about how ctDNA testing can be integrated into routine clinical management for mBC patients. In a new study, NBCF-funded researcher Professor Sarah-Jane Dawson (Peter MacCallum Cancer Centre) recently established a ctDNA testing program for patients with mBC to investigate how it might work.
The study, published recently in the journal PLOS Medicine, enrolled 234 mBC patients (232 women, 2 men) and followed them for an average of 15 months. ctDNA blood tests were taken from all patients at the beginning of the study, and then at intervals of 4 or more weeks, if clinically required.
Throughout the study, the team found that 44% of patients (104 of 234) had an actionable mutation (a change in a gene that would potentially make the cancer responsive to a targeted therapy). Moreover, the ctDNA testing directly affected the clinical management of 40 patients – this means the patient was either enrolled on an available clinical trial, or their clinicians changed their treatment strategy as a direct consequence of the ctDNA result.
“Our results clearly show how clinical management can be guided by ctDNA testing”, Prof Dawson explained. “For example, one patient in our study was initially diagnosed with HER2- metastatic breast cancer through a routine tissue biopsy; subsequent liquid biopsies revealed the emergence of HER2+ disease, which was confirmed by additional medical tests. Consequently, HER2-targeted treatment was started, resulting in near complete response in the patient after 2 months.”
Overall, this study showed that breast cancer-specific ctDNA testing from liquid biopsies is a useful approach for real time disease monitoring that complements standard clinical management. Although further scientific and clinical study is needed before liquid biopsies can be widely used to routinely monitor breast cancer patients, this study represents a step forward towards the practical implementation of liquid biopsies to further improve and personalise the clinical treatment of mBC patients.