Cancer diagnostic developer Oncocyte is pioneering early-stage detection with novel RNA-based tests for lung cancer. Limitations of Current Biomarkers Most blood-based early cancer detection diagnostics in development are based on the analysis of cell-free and tumor-circulating DNA. In order for tumor DNA to be present in the blood of a cancer patient, however, the tumor must be quite large. These diagnostics, therefore, typically only detect mid- to late-stage cancers, and await demonstration that early detection of these large tumors impacts outcomes.