Detection of mutations in circulating free DNA in patients with breast cancer

• Published in: Breast cancer research and treatment 2010-01, Vol.120 (2), p.461-467
• Main Authors: Board, Ruth E., Wardley, Andrew M., Dixon, J. Michael, Armstrong, Anne C., Howell, Sacha, Renshaw, Lorna, Donald, Emma, Greystoke, Alastair, Ranson, Malcolm, Hughes, Andrew, Dive, Caroline
• Format: Article
• Language: English
• ISSN: 0167-6806; 1573-7217
• DOI: 10.1007/s10549-010-0747-9

Somatic mutations in (encoding a class I phosphoinositide 3 kinase (PI3K) subunit) modulate PI3K signalling to influence tumour behaviour and occur in up to 40% of breast cancers. Inhibitors of PI3K signalling are entering clinical trials, but the impact of mutation on tumour response has yet to be clarified. This study investigated the potential utility of circulating free DNA (cfDNA) as a source for mutation detection in patients with breast cancer. cfDNA extracted (QIAamp Virus spin kit) from blood and matched archival tumour from 46 patients with metastatic breast cancer and 30 patients with localised, operable breast cancer was assessed for hotspot mutations using Amplification Refractory Mutation System (ARMS) allele-specific PCR and Scorpion probes. mutations were detected in 13/46 (28%) plasma-derived and 10/46 (21%) serum-derived cfDNA samples from metastatic breast cancer patients. In 41 cases with matched tumour and plasma-derived cfDNA data, concordance (same mutation status in plasma and tumour) was 95%. Where a mutation was present in tumour, the ‘pick up' in plasma-derived cfDNA was 80%. mutations were present in tumours from 14/30 (47%) localised breast cancers, but no PIK3CA mutations were detected in matched cfDNA. These data demonstrate feasibility and potential utility of cfDNA for mutation detection in patients with metastatic breast cancer. Studies are underway to qualify PIK3CA mutation in cfDNA as a predictive biomarker allowing patient stratification in clinical trials of mechanism-based therapeutics that target PI3K signalling pathways.