Guidelines for Imaging Peritoneal Metastases in Ovarian and Colorectal Cancer
Overview
Radiological imaging is essential for detecting and managing peritoneal metastases (PM) in ovarian and colorectal cancer. CT is widely used for initial assessment despite limitations, while MRI offers superior accuracy for evaluating PM extent. FDG PET/CT aids in detecting extraperitoneal metastases but is less reliable for small or hypometabolic lesions.
Background
Peritoneal metastases are common in ovarian and colorectal cancers, significantly impacting prognosis and treatment decisions. In colorectal cancer, PM occur in 6% at diagnosis and up to 21% in recurrence, while 80% of ovarian cancer patients present with peritoneal disease due to late symptom onset. Accurate assessment of PM extent, often using the Peritoneal Cancer Index (PCI), guides eligibility for cytoreductive surgery and chemotherapy. Imaging challenges include small lesion size and obscuration by ascites or adjacent organs, often necessitating invasive surgical staging.
Most accurate for PM extent; aids surgical selection
100%
Low–moderate
FDG PET/CT
Detects extraperitoneal metastases; limited for small/hypometabolic lesions
100%
Low–moderate
Whole-body MRI & FDG PET/CT
Problem-solving in suspected PM/recurrence; detects missed extraperitoneal metastases
100%
Low–moderate
Key Findings
CT is the most accessible imaging modality but underestimates small or isodense peritoneal metastases, limiting surgical selection accuracy.
MRI provides the highest accuracy for assessing PM extent and is valuable for surgical decision-making at diagnosis, post-chemotherapy, or recurrence.
FDG PET/CT is insufficiently sensitive for preoperative staging of PM but useful for identifying extraperitoneal disease.
Standardized imaging protocols and reporting, including use of PCI and tools like PROMISE and PAUSE, improve communication and treatment planning.
Multidisciplinary tumor board discussions involving experienced radiologists are recommended for all patients with PM.
Imaging protocols for PM do not differ between colorectal and ovarian cancer.
Clinical Implications
Clinicians should utilize CT for initial and follow-up imaging due to its availability but consider MRI for detailed assessment when surgical planning is critical. FDG PET/CT should be reserved for detecting extraperitoneal metastases rather than primary PM evaluation. Standardized reporting and multidisciplinary collaboration enhance treatment decision-making and patient outcomes.
Conclusion
Imaging of peritoneal metastases in ovarian and colorectal cancer requires a multimodal approach with CT, MRI, and FDG PET/CT tailored to clinical needs. Adoption of standardized protocols and multidisciplinary evaluation optimizes patient selection for surgery and systemic therapies.
References
ESGAR, ESUR, PSOGI, EANM Collaborative Guidelines 2024 -- Imaging Peritoneal Metastases in Ovarian and Colorectal Cancer
by Vincent Vandecaveye, Pascal Rousset, Stephanie Nougaret, Artem Stepanyan, Milagros Otero-Garcia, Olivera Nikolić, Maira Hameed, Karolien Goffin, Ignace H. J. de Hingh, Max J. Lahaye
Radiologists assigned to receive step-by-step explanations from a large language model achieved higher diagnostic accuracy in a randomized vignette study, while differential-diagnosis outputs may have increased inappropriate reliance on incorrect model suggestions.
