In conclusion, the inverse correlation of DTCs (by CK19 qRT-PCR) in the bone marrow with the larger 291-bp amplicon in cfDNA indicates that the dormancy period of breast cancer is potentially characterised by two distinct phases: one in which measures of viable DTCs are absent, during which measures of cell death manifesting as cfDNA in the blood are evident, and an alternate phase, characterised by evidence of viable DTCs, but lower levels of cfDNA. The gene discussed is KRT19; the disease is breast cancer.