Abstract: The invention provides methods for preparing a preparation of amplified DNA derived from a biological sample of a patient who has been diagnosed with cancer useful for determining relapse or metastasis of cancer, comprising (a) sequencing DNA isolated from hematopoiesis cells in a blood or bone marrow sample of the patient or a fraction thereof to determine the presence or absence of one or more clonal hematopoiesis of indeterminate potential (CHIP) mutations; (b) sequencing (i) DNA isolated from a tumor biopsy sample of the patient or (ii) cell-free DNA isolated from the blood or bone marrow sample or a fraction thereof, to identify a plurality of patient-specific somatic mutations associated with the cancer; (c) preparing a preparation of amplified DNA by performing targeted multiplex amplification on cell-free DNA isolated from a longitudinally collected biological sample of the patient or a fraction thereof to amply a plurality of target loci to obtain amplified DNA, wherein each of the target loci spans