For instance, the current standard of care for the diagnosis of cancer relies upon examining tissue taken from an invasive biopsy procedure. These procedures can be very painful, can lead to infections, and can often result in other harmful side effects. Sampling error (the biopsy needle misses the target), tumor heterogeneity, and limited tissue access (lack of adequate sample) for analysis and inter- and intra-observer variability of pathology review are confounding factors affecting the accuracy of biopsy evaluation.
To date the search for blood-based (epi)genomic markers of solid tumors has mainly focused on circulating tumor cells (CTCs) and cell free DNA and nucleic acids (cfDNA;cfNA), which leads to issues with insufficient sensitivity. In prostate cancer, blood-based liquid biopsy tests have focused on proteins such as kallikrein markers, which lack specificity when trying to identify men at risk.