SEPTIN9 and colorectal carcinoma: Postoperative methylated septin 9 in plasma may represent a potential noninvasive biomarker for CRC recurrence monitoring in addition to CRC diagnosis and prognosis compared with CEA and CA19-9.57 The circulating tumor DNA (ctDNA) minimal residual disease (MRD) following treatment in solid tumors predicts relapse and highlights the application of this potentially transformative biomarker.58