Haystack MRD™ is a tumor-informed, liquid biopsy test that begins with tumor whole-exome sequencing (WES) to identify patient-specific somatic mutations. A personalized MRD test is then developed to detect ctDNA, which indicates the presence of residual, recurrent, or resistant disease. The test is purpose-built for ultra-sensitive ctDNA detection in patients with solid tumors and can be used to detect residual disease to guide adjuvant therapy, to monitor treatment response, and for recurrence surveillance.