Positron Emission Tomography/Magnetic Resonance Imaging (PET/MRI) Versus the Standard of Care Imaging in the Diagnosis of Peritoneal Carcinomatosis.

Objective: To compare positron emission tomography (PET)/magnetic resonance imaging (MRI) to the standard of care imaging (SCI) for the diagnosis of peritoneal carcinomatosis (PC) in primary abdominopelvic malignancies.

Summary Background Data: Identifying PC impacts prognosis and management of multiple cancer types.

Methods: Adult subjects were prospectively and consecutively enrolled from April 2019 to January 2021. Inclusion criteria were: 1) acquisition of whole-body contrast-enhanced (CE) 18F-fluorodeoxyglucose PET/MRI, 2) pathologically confirmed primary abdominopelvic malignancies. Exclusion criteria were: 1) greater than 4 weeks interval between SCI and PET/MRI, 2) unavailable follow-up. SCI consisted of whole-body CE PET/computed tomography (CT) with diagnostic quality CT, and/or CE-CT of the abdomen and pelvis, and/or CE-MRI of the abdomen±pelvis. If available, pathology or surgical findings served as the reference standard, otherwise, imaging followup was used. When SCI and PET/MRI results disagreed, medical records were checked for management changes. Follow-up data were collected until August 2021.

Results: One hundred sixty-four subjects were included, 85 (52%) were female, and the median age was 60 years (interquartile range 50-69). At a subject level, PET/MRI had higher sensitivity (0.97, 95% CI 0.86-1.00) than SCI (0.54, 95% CI 0.37-0.71), P < 0.001, without a difference in specificity, of 0.95 (95% CI 0.90-0.98) for PET/MRI and 0.98 (95% CI 0.93-1.00) for SCI, P ¼ 0.250. PET/MRI and SCI results disagreed in 19 cases. In 5/19 (26%) of the discordant cases, PET/MRI findings consistent with PC missed on SCI led to management changes.

Conclusion: PET/MRI improves detection of PC compared with SCI which frequently changes management.