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Genomics of Circulating Tumor Cells

Comprehensive analyses of cancer genomes in clinical settings promise to inform prognoses and guide the deployment of precise cancer treatments. A major barrier, however, is the inaccessibility of adequate metastatic tissue for accurate genomic analysis in prostate and other cancers. A potential solution is to characterize circulating tumor cells (CTCs), but this requires overcoming multiple technical hurdles. Here, we report an integrated process to isolate, qualify, and sequence whole exomes of CTCs with high fidelity, using a census-based sequencing strategy. Power calculations suggest that mapping of over 99.995% of the territory accessible in bulk exome sequencing is possible in CTCs. We validated our sequencing process in two prostate cancer patients including one for whom we compared CTC-derived mutations to mutations found in a lymph node metastasis and nine cores of the primary tumor. 51 of 73 CTC mutations (70%) were observed in matched tissue. Moreover, we identified 10 early trunk mutations and 56 metastatic trunk mutations in the non-CTC tumor samples and found 90% and 73% of these, respectively, in CTC exomes. This study establishes a foundation for CTC genomics in the clinic.