The increased importance of cancer genotyping in guiding cancer treatment has created a need for efficient methods for genomic analysis of patients鈥� cancers. This increased dependence on DNA-based tumor genotyping assays (eg, sequencing, polymerase chain reaction [PCR], fluorescence in situ hybridization [FISH]) has triggered a growing interest in the analysis of free-floating DNA present in the blood of patients with cancer鈥攑lasma cell-free DNA (cfDNA). Sensitive PCR techniques together with high-throughput next-generation sequencing (NGS) technologies have evolved to a point where genetic analysis of cfDNA is possible.

Genotyping of plasma cfDNA is compelling for a number of reasons.¹ Most importantly, it can noninvasively provide clinically-relevant genomic information that is usually only available after an invasive tumor biopsy procedure. It can be very fast²鈥攖he blood specimen is sent directly to a molecular laboratory for DNA analysis, potentially faster than the complex journey of a tumor specimen from scheduled biopsy procedure to pathology review to molecular testing. Plasma genotyping can be highly quantitative, such that measurement of key cancer genes can potentially offer cancer-specific information on the response to therapy.³ The method is readily scalable given the relative ease of specimen processing and handling. Finally, plasma specimens do not undergo formalin fixation, resulting in a reduced level of background 鈥渘oise鈥� compared with analysis of DNA from formalin-fixed tumor specimens.