Colorectum is the most common site of metastasis in ovarian cancer. Regarding intestinal surgery, there is controversy over whether to choose bowel resection or tumor removal, and currently, there are no prospective randomized controlled studies comparing the oncological safety of these two surgical approaches. This study is a prospective randomized trial aimed at comparing the efficacy of rectosigmoid resection versus rectosigmoid-preserving lesion excision in advanced ovarian cancer surgery.

Gastrointestinal surgeries, such as intestinal resection and anastomosis, ileostomy and/or colostomy, have become an important step in more than 50% of advanced ovarian cancer tumor cell reduction surgeries. Among them, the sigmoid colon rectum is the main intestinal site affected by ovarian cancer metastasis. To achieve R0 tumor reduction surgery, partial sigmoid colon rectum resection is often performed simultaneously. However, approximately 2.3-6.8% of patients undergoing this surgery have intestinal anastomotic leakage, 17-18% of patients require prophylactic or permanent colostomy, and 40% of patients will experience changes in bowel habits and other rectal anterior low resection syndrome after surgery, which reduces the quality of life of the patients.

Numerous studies have found that the rectosigmoid colon involvement in ovarian cancer mainly occurs in the serosa, followed by the muscular layer, and finally the mucosa. Moreover, in 80% of cases, the involvement is limited to the seromuscular layer. Therefore, some studies have suggested that for seromuscular layer infiltration, resection of the rectosigmoid colon during cytoreductive surgery may not be necessary, and partial resection of the intestinal wall or tumor enucleation can be considered. Although tumor enucleation can preserve the rectosigmoid colon when it is involved, some studies have raised concerns about its oncological safety. These studies argue that not resecting the rectosigmoid colon may leave microscopic tumor residues, leading to a decrease in survival rates. In contrast, recent retrospective clinical studies have supported that, compared with intestinal resection, tumor enucleation of the rectosigmoid colon does not affect the prognosis of advanced ovarian cancer. Regarding intestinal metastasis of ovarian cancer, the current National Comprehensive Cancer Network(NCCN) guidelines for ovarian cancer state that preoperative neoadjuvant chemotherapy does not improve survival and therefore do not recommend it. Instead, the guidelines suggest direct surgical treatment. As for the surgical approach, the guidelines only require achieving R0 resection of the intestinal tumor, without specifying whether it is intestinal segment resection or tumor enucleation. Therefore, both rectosigmoid colon resection and tumor enucleation while preserving the rectosigmoid colon are common surgical methods in clinical practice. The investigator analyzed 130 cases of advanced ovarian cancer treated surgically in the investigator's hospital from 2015 to 2021, comparing the rectosigmoid colon resection group with the tumor enucleation group while preserving the rectosigmoid colon. The investigator found no difference in progression-free survival between the two groups, a conclusion consistent with published studies.

As there are currently no prospective randomized controlled studies comparing the oncological safety of these two surgical approaches, this study is a prospective randomized study comparing the efficacy of rectosigmoid resection and rectosigmoid-sparing tumor debulking in advanced ovarian cancer surgery. It was designed and led by the Second Affiliated Hospital of Zhejiang University School of Medicine, with the participation of multiple domestic hospitals. The study strictly adheres to Good Clinical Practice(GCP) requirements, is strictly managed, and records data truthfully to provide genuine and scientific research data. This study will provide satisfactory cytoreductive surgery and standardized treatment for enrolled patients, ensuring the patients's benefits. The study will provide reliable clinical evidence for the management of the intestinal tract in cytoreductive surgery for advanced ovarian cancer and introduce new surgical methods to improve the prognosis and quality of life of ovarian cancer patients.

Inclusion Criteria:

• Voluntarily participate in this study and sign the informed consent form;
• Age 18-70 years old;
• Primary debulking surgery for epithelial ovarian cancer (including neoadjuvant chemotherapy), with or without abdominal and distant metastasis (≥ IIB stage);
• Colonoscopy negative (no mucosal layer invasion);
• Preoperative imaging (enhanced pelvic MRI) assesses the tumor's involvement of the intestinal surface and/or major parts of the mesentery;
• Eastern Cooperative Oncology Group (ECOG) score < 3;
• American Society of Anesthesiologists (ASA) score < 3.

Exclusion Criteria:

• Has a history of other malignant tumors or is undergoing other anti-tumor treatments;
• Has severe underlying medical conditions that make surgery intolerable;
• Epithelial ovarian cancer diagnosed incidentally during emergency surgery;
• Participates in other clinical studies simultaneously;
• Secondary cytoreductive surgery for epithelial ovarian cancer;
• Patients who have received radiotherapy to the abdomen or pelvis before.