Mutation Analysis Of Cell-Free Dna Captures Heterogeneity Of Individual Circulating Tumor Cells In Metastatic Breast Cancer

Circulating tumor cells (CTCs) are more technically challenging to isolate and characterize than circulating cell-free DNA (cfDNA). However, analysis of single CTCs may reveal more actionable information to guide targeted therapies than mutation tracking in cfDNA. Here, we compared CTC count with cfDNA levels in 113 patients with metastatic breast cancer. In 5 patients we compared mutations in 40 individual CTCs and matched cfDNA using targeted amplicon sequencing of 54 genes (∼2800 COSMIC mutations) at u003e2500x mean read depth. Total cfDNA levels were significantly associated with overall survival (hazard ratio (HR), 2.2; 95% CI, 1.1 to 4.3; P = 0.021) and correlated with CTC counts (P = 0.002). Four patients had mutations detected in cfDNA, the levels of which tracked with levels of circulating tumor DNA (ctDNA). Mutational heterogeneity was seen across individual CTCs (including mutations in PIK3CA, ESR1 and KRAS) and was reflected in matched cfDNA, but cfDNA had other mutations not seen in CTCs (including TP53). Therefore, cfDNA reflects persisting CTCs and enables monitoring of the metastatic burden for clinical decision-making when CTCs cannot be obtained. Moreover, monitoring of total cfDNA levels could provide an inexpensive and simple measure of treatment response. Citation Format: David S. Guttery, Jacqueline A. Shaw, Allison Hills, Daniel Fernandez-Garcia, Karen Page, Brenda Rosales, Kate Goddard, Robert Hastings, Jinli Luo, Olivia Ogle, Laura Woodley, Simak Ali, Justin Stebbing, Charles Coombes. Mutation analysis of cell-free DNA captures heterogeneity of individual circulating tumor cells in metastatic breast cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr LB-339.