TK1 is a key enzyme in DNA precursor synthesis. It is upregulated during the S phase of the cell cycle. Increased levels of TK1 in blood is an indicator of active cell proliferation and disruption as a consequence of increased turnover and cytotoxic effects. AroCell TK 210 ELISA requires only a simple liquid biopsy and is a quick and simple assay to determine TK1 in blood. Tk1 is a potential biomarker for precision monitoring in cancer care.