Background Gastric cancer (GC) is the fourth leading cause of cancer mortality worldwide. Peritoneal metastasis (PM) is a significant cause of death in patients with GC, and presents a major challenge in clinical diagnosis and treatment. Predicting the occurrence of PM in high-risk patients, and diagnosing and treating PM in advance to improve patient survival, remains an unsolved problem in clinical practice. Given the low positive rate of cytology and difficulty in diagnosing occult PM, new molecular markers and detection technologies for early diagnosis require urgent validation. The primary objective of this study is to observe and evaluate the predictive effect of intraoperative peritoneal lavage fluid (PLF) circulating tumour cells (CTC) and circulating tumour DNA (ctDNA) levels in patients with pT4NxM0/pT1-3N+M0 GC on metachronous PM after R0 resection. Methods and analysis This prospective single-centre clinical study is conducted at Renji Hospital, Shanghai Jiao Tong University School of Medicine. In this study, 200 cases of patients with pT4NxM0/pT1-3N+M0 gastric adenocarcinoma older than 18 years will be screened. Participants will undergo intraoperative PLF CTC and ctDNA testing and will be followed up for 2 years, with imaging assessments performed every 3–6 months until PM occurrs. The primary outcome is the incidence of PM 1 year after surgery, which will be estimated using Clopper-Pearson method, with 95% CIs calculated and compared between groups. Secondary outcome include the incidence of PM 2 years after surgery, overall survival and disease progression. Data will be analysed using the Kaplan-Meier method and the log-rank test. Ethics and communication Informed consent has been obtained from all subjects. This protocol has been approved by the Ethics Committee of Renji Hospital, Shanghai Jiao Tong University School of Medicine (LY2023-142-B). The findings will be disseminated through peer-reviewed manuscripts, reports and presentations. Trial registration number ChiCTR2300074910.

Introduction Immunotherapy has revolutionised cancer treatment. Immune checkpoint inhibitors have demonstrated significant efficacy across multiple tumour types, including gastric cancer, where several approved programmed cell death 1/programmed cell death-ligand 1 (PD-1/PD-L1) inhibitors show promising antitumour activity. While PD-L1 expression serves as a predictive biomarker for PD-1 inhibitor response, and PD-L1-positive patients generally show better outcomes, therapeutic resistance remains a challenge. Many initial responders eventually develop resistance, and surprisingly, some PD-L1-positive patients fail to achieve expected response rates, indicating emerging resistance mechanisms in potentially responsive populations. Adebrelimab, a PD-L1 inhibitor, demonstrates mechanistic advantages over PD-1 inhibitors, with clinical studies suggesting promising therapeutic potential. When combined with irinotecan, apatinib has shown efficacy in second-line gastric cancer treatment. This study aims to evaluate the efficacy and safety of combining adebrelimab with apatinib and irinotecan for advanced gastric cancer refractory to PD-1 inhibitors. Method and analysis This single-arm, single-centre exploratory trial will be conducted at Renji Hospital, enrolling 32 patients aged 18–75 years. Eligible patients must have initially achieved partial response, complete response or stable disease with progression-free survival (PFS)≥3 months during prior immunotherapy but subsequently progressive disease on imaging. Treatment will continue until meeting discontinuation criteria. The primary endpoint is objective response rate with Clopper-Pearson 95% CI. Secondary endpoints include disease control rate (95% CI), PFS and overall survival (estimated by Kaplan-Meier method), along with safety assessments. Ethics and dissemination All participants will provide informed consent. The protocol has been approved by the Shanghai Jiaotong University School of Medicine, Renji Hospital Ethics Committee (LY2023-201-C). The results will be disseminated through peer-reviewed manuscripts, reports and presentations. Trial registration number ChiCTR2300077329.

Background Prophylactic ileostomy plays a critical role in the radical resection of low rectal cancer, but the incidence of stoma site incisional hernia (SSIH) after stoma closure remains high. No study has been reported in which radiomics has been used to predict SSIH. The primary aim of this study is to evaluate the safety and efficacy of biological mesh in preventing incisional hernia in patients with high-risk incisional hernia factors, as identified by image-based deep learning model, undergoing ileostomy closure surgery. Methods and analysis 40 patients who need to undergo ileostomy closure and have been identified with high risk factors for SSIH by image-based deep learning model will be selected for this study. Patients will be randomly assigned equally to the prophylactic biological mesh placement group and the control group, and outcomes will be tracked via clinic review at 1 month, 3 months, 6 months and 12 months postoperatively. The outcome measures are the rate of postoperative incisional hernia, local pain, incisional infection, seroma and so on. This study demonstrates that prophylactic placement of biological mesh with ileostomy closure reduces the incidence of SSIH. Furthermore, it validates the feasibility of image-based deep learning models in predicting postoperative complications and identifying high-risk SSIH patients. Ethics and dissemination Informed consent has been obtained from all subjects. This protocol has been approved by the Ethics Committee of Renji Hospital, Shanghai Jiao Tong University School of Medicine (KY2022-087-B). The findings will be disseminated through peer-reviewed manuscripts, reports and presentations. Trial registration number ChiCTR2200064995. Registration date: October 2022. Registration authority: Chinese Clinical Trial Registry.

DNA methylation is a key epigenetic modification catalyzed by DNA methyltransferases (DNMTs) and predominantly occurs at cytosine-phosphate-guanine (CpG) islands, which are often located in gene promoter regions. Hypermethylation of CpG islands within gene promoters can silence tumor suppressor gene expression, thereby disrupting normal cellular functions, including maintenance of genomic stability and regulation of cell growth, and contributing to tumor initiation and progression. In contrast, global hypomethylation may promote genomic instability and oncogene activation. This review discusses the molecular mechanisms underlying DNA methylation and evaluates its functional and clinical significance in colorectal and gastric cancers, with emphasis on its potential application as a noninvasive biomarker for diagnosis.