Sample collection, DNA isolation, and library preparation
MSI, tumor, Tumor, cancer, primary cancer
TUMOR, TUMOR, CANCER, MICROSATELLITE INSTABILITY, CAVITY, PRIMARY TUMOR, PRIMARY CANCER
Peritoneal lavage was collected after entering abdominal cavity during primary cancer surgery by laparotomy or laparoscopy in all enrolled patients. 300 ml of normal saline was infused into abdominal cavity through a small opening in the abdominal wall or laparoscopic trocar. About 100 ml of peritoneal lavage was aspirated for cfDNA sequencing. Then, resection of primary tumor was performed by surgeons. Peripheral blood was collected and saved in anticoagulant blood collection tube (EDTA tubes) in routine temperature. Tumor tissue specimens were obtained from resected tumor tissues. The percent of cancer cells by HE staining was ≥ 20%. If not, tumor mutational burden (TMB), CNV and microsatellite instability (MSI) tests may be affected.DNA isolation and targeted sequencing were performed in Burning Rock Biotech (Shanghai, China), according to optimized protocols described previously [