Diagnostic performance of imaging for the detection of peritoneal metastases: a meta-analysis.

PURPOSE: Detection of peritoneal metastases (PM) is key in the staging and management of gastrointestinal and ovarian cancer patients. The purpose of this meta-analysis was to determine the diagnostic performance of CT, PET(CT), and (DW)MRI in detecting PM. METHODS: A literature search in Pubmed, Embase (Ovid), and Scopus was performed (January 1997-May 2018) to identify studies reporting on the accuracy of imaging PM in the diagnostic workup of gastrointestinal or ovarian cancers. Inclusion criteria were region-based or patient-based studies comprising > 15 patients, surgery/histology/radiological follow-up as a reference standard, and sufficient data to construct a 2 × 2 contingency table. Two observers performed data extraction. The sensitivity, specificity, and diagnostic odds ratio (DOR) were calculated using a bivariate random-effects model and hierarchical summary operating curves (HSROC) were generated. RESULTS: Of 3457 citations retrieved, twenty-four articles met all inclusion criteria. Thirty-seven datasets could be extracted for analysis including 20 for CT, 10 for PET(CT), and 7 for (DW)MRI. The pooled sensitivity, specificity, and DOR for the detection of PM for region-based studies for CT were 68% (CI, 46-84%), 88%(CI, 81-93%), and 15.9 (CI, 4.4-58.0) respectively; 80% (CI, 57-92%), 90% (CI, 80-96%), and 36.5 (CI, 6.7-199.5) for PET(CT), respectively; 92% (CI, 84-96%), 85% (CI, 78-91%), 63.3 (CI, 31.5-127.3) for (DW)MRI. In the patient-based group, not enough studies were included to make a pooled analysis for (DW)MRI and PET(CT). CONCLUSION: (DW)MRI and PET(CT) showed comparable diagnostic performance for the detection of peritoneal metastases in ovarian and gastrointestinal cancer patients. Since MRI is more widely available than PET(CT) in clinical practice, this potentially is the imaging method of choice in most centers in the future. KEY POINTS: • Detection of peritoneal metastases plays an important role in the accurate staging of cancer patients, however, there is no accepted reference standard for the imaging of peritoneal metastases • This meta-analysis shows that (DW)MRI provided the highest sensitivity for the detection of peritoneal metastases in ovarian and gastrointestinal cancer patients • Although (DW)MRI and PET(CT) show a comparable overall diagnostic performance, (DW)MRI seems to be the imaging method of choice since it is more available in daily practice than PET(CT).

Diffusion-weighted MRI assessment of the peritoneal cancer index before cytoreductive surgery.

BACKGROUND: Patients with limited peritoneal metastases from colorectal cancer may be candidates for an aggressive surgical approach including cytoreductive surgery and hyperthermic intraperitoneal chemotherapy (CRS-HIPEC). Selection is based on surgical inspection during laparoscopy or laparotomy. The aim of this study was to investigate whether diffusion-weighted MRI (DW-MRI) can be used to select patients for CRS-HIPEC. METHODS: This was a prospective study at a tertiary referral centre. Patients with confirmed or suspected colorectal peritoneal metastases scheduled for exploratory laparotomy or laparoscopy were eligible. Two radiologists assessed the peritoneal cancer index (PCI) on CT (CT-PCI) and DW-MRI (MRI-PCI). The reference standard was PCI at surgery. Radiologists were blinded to the surgical PCI and to each other's findings. The main outcome was the accuracy of DW-MRI in predicting whether patients had resectable disease (PCI less than 21) or not. RESULTS: Fifty-six patients were included in the study, of whom 49 could be evaluated. The mean(s.d.) PCI at surgery was 11·27(7·53). The mean MRI-PCI was 10·18(7·07) for reader 1 and 8·59(7·08) for reader 2. Readers 1 and 2 correctly staged 47 of 49 and 44 of 49 patients respectively (accuracy 96 and 90 per cent). Both readers detected all patients with resectable disease with a PCI below 21 at surgery (sensitivity 100 per cent). No patient was overstaged. The intraclass correlation (ICC) between readers was excellent (ICC 0·91, 95 per cent c.i. 0·77 to 0·96). MRI-PCI had a stronger correlation with surgical PCI (ICC 0·83-0·88) than did CT-PCI (ICC 0·39-0·44). CONCLUSION: DW-MRI is a promising non-invasive tool to guide treatment selection in patients with peritoneal metastases from colorectal cancer.

Seeing the whole picture: Added value of MRI for extraperitoneal findings in CRS-HIPEC candidates.

PURPOSE: In colorectal cancer (CRC) patients the selection of suitable cytoreductive surgery and hyperthermic peritoneal chemotherapy (CRS-HIPEC) candidates is based on the location and extent of peritoneal metastases (PM) and presence of extraperitoneal metastases. MRI is increasingly being used to accurately assess the extent of PM, however, the significance of extraperitoneal findings in these scans has never been evaluated before. METHODS: CRC patients who had undergone an additional MRI scan after standard work-up with CT for preoperative staging between January 2016-January 2020 were selected. CT and MRI reports were reviewed for new abdominopelvic extra-peritoneal findings on MRI (MR-EPF) and MR-EPFs concerning lesions previously indicated as equivocal (uncertain benign/malignant) on CT. Reference standard were surgical results or follow-up imaging. RESULTS: In 158 included patients 60 MR-EPFs (in 58/158 patients) were noted: twenty-six (43%) were new findings and thirty-four (57%) were equivocal findings on CT. Of the 34 equivocal findings 27 were 'rejected/less likely malignant' and 7 'confirmed/more likely malignant' based on MRI. In 29 patients (18%) the MR-EPFs had direct influence on treatment planning. Three patients (2%), eligible for CRS-HIPEC on CT, were deemed inoperable due to MR-EPFs. CONCLUSION: MRI had an added value in more than a third of the patients due to abdominopelvic extraperitoneal findings that were undetected or indeterminate on CT and therefore influenced the treatment in a substantial part of the patients. Combined with the known accurate detection of peritoneal disease on MRI, MRI seems a logical addition to the diagnostic workup of potential CRS-HIPEC candidates.

MRI with diffusion-weighted imaging to predict feasibility of complete cytoreduction with the peritoneal cancer index (PCI) in advanced stage ovarian cancer patients.

OBJECTIVES: To determine the diagnostic performance of MRI with diffusion-weighted imaging (DW-MRI) in assessing the peritoneal tumor load and predicting whether a complete cytoreduction can be achieved in patients with epithelial ovarian cancer (EOC). METHODS: For this observational prospective study, 25 patients with epithelial ovarian cancer scheduled for cytoreductive surgery were included. Patients underwent a 3 T DW-MRI scan prior to surgery. The MR protocol consisted of a T1 and T2 weighted, a contrast-enhanced T1 weighted, and a diffusion-weighted (b0, b1000) sequence. The Peritoneal Cancer Index (PCI) was determined on DW-MR images (MRI-PCI) by two readers, independently, and was compared to the PCI determined during surgery (S-PCI). The inter-observer agreement between the two radiologists was evaluated. In addition, receiver operating characteristics curves were calculated for predicting complete cytoreduction with the S-PCI and MRI-PCI. RESULTS: Staging with DW-MRI showed a correlation to surgical staging with an intraclass correlation coefficient (ICC) 0.86 and 0.85 for reader 1 and 2, respectively. Inter-observer agreement was excellent with an ICC of 0.90 (95% CI: 0.64-0.96). The MRI-PCI scores of reader 1 (AUC = 0.96), reader 2 (AUC = 0.98), and the S-PCI (AUC = 0.92) showed similar predictive values for complete cytoreduction. CONCLUSION: DW-MRI is accurate in predicting the S-PCI and can be helpful to predict whether a complete resection in ovarian cancer patients is feasible.