Review question / Objective: Population： Solid tumors (stomach cancer, liver cancer, biliary cancer, esophageal cancer, head and neck cancer, pancreatic cancer, o v a r i a n c a n c e r, c e r v i c a l c a n c e r, endometrial cancer, bladder cancer, urothelium carcinoma). Predictive factors: c t D N A d e t e c t e d ; I n t e r v e n t i o n / comparator： No limitation. Outcomes： Primary outcomes: Progression-free survival (PFS); Include Relapse-free survival (RFS)、Disease free survival (DFS)、DMFS (Distant Metastasis-Free Survival)、Eventfree survival(EFS). Overall survival (OS).