Diffusion-weighted magnetic resonance imaging (DWI/MRI) has been described in recent literature as a highly sensitive and specific modality for the detection of peritoneal metastases PM. It has been demonstrated to be superior to CT for patients with known peritoneal disease from colorectal and gynaecological malignancies as a staging tool for cytoreductive surgery. It was also demonstrated to be superior for the detection of PM for gastric cancer patients otherwise considered with a resectable tumor. However, the literature is scarce on the role of DWI/MRI in the detection of peritoneal recurrence for patients with high-risk features, either colorectal cancer (CRC) or appendiceal neoplasms (AN).

The aim of this study is to prospectively assess the added value of whole-body DWI/MRI (WB-DWI/MRI) to CT and diagnostic laparoscopy for detection of PM in the follow-up of patients presenting with CRC or AN and high-risk features for peritoneal recurrence and evaluate how it correlates with intraoperative findings.

This is a multicentric, prospective study (CHU de Québec and Hôpital Maisonneuve-Rosemont). Patients will be referred to one of six surgeons with a subspeciality in peritoneal surface oncology after their index surgery for CRC or AN. After thorough assessment, patients judged without residual peritoneal disease, but at high-risk for peritoneal recurrence, will be prospectively included in the study. Patients will be assessed with CT and WB-DWI/MRI twelve months after their index surgery. For WB-DWI/MRI, the standard protocol will include the following sequences: Patients will drink 1L of pineapple juice one hour prior to the examination in order to provide a negative intraluminal contrast. They will receive 20 mg of intravenous hyoscine butylbromide at the beginning of the MR exam in order to reduce bowel peristalsis. Sequences will include Axial et Coronal T2WI of the abdomen and pelvis, axial DWI with b values of 0, 50 and 1000 of the abdomen and pelvis, as well as Pre and post gadolinium-based contrast Axial and Coronal 3D T1WGRE. All patients included in the study will then undergo diagnostic laparoscopy, to provide correlation with imaging findings. Patients with no evidence of peritoneal recurrence on CT, WB-DWI/MRI and diagnostic laparoscopy will continue to be followed with serial CT and blood tumor markers (CEA, CA 19-9) as done on a routine basis. Patients with confirmed peritoneal disease at diagnostic laparoscopy will be further evaluated for cytoreductive surgery, with or without hyperthermic intraperitoneal chemotherapy. The study duration will be two years for all participants.

Inclusion Criteria:

• Confirmed diagnosis of colorectal cancer or high-risk appendiceal neoplasm (High grade Appendiceal Mucinous Neoplasm (HAMN), goblet-cell carcinoma or adenocarcinoma).

• No evidence of residual peritoneal disease based on referring surgeon operating report and preoperative imaging.

• At least one high-risk feature for peritoneal recurrence, including:

  • Synchronous peritoneal metastases resected at index surgery;
  • Synchronous ovarian metastases resected at index surgery;
  • Perforated primary tumor.

• No evidence of distant metastases.

• Patient fit for cytoreductive surgery, if required (ECOG 0 or 1).

Exclusion Criteria:

• Unresected synchronous peritoneal metastases at referral.
• Low grade Appendiceal Mucinous Neoplasm (LAMN).
• No high-risk feature for peritoneal recurrence.
• Evidence of distant metastases on preoperative imaging.
• Patient who is unable to have MRI.
• Patient unfit for cytoreductive surgery, if required (ECOG 2 or more).