(PM P18) Interim Results of Phase II Trial for Novel Magnetic Resonance Imaging of Peritoneal Mesothelioma

Background: Current cross-sectional imaging demonstrates poor sensitivity for peritoneal disease. We report interim results of a novel method utilizing high resolution (HR) MRI to detect malignant peritoneal mesothelioma (MPM).

Methods: Patients with MPM undergoing laparoscopy/laparotomy were enrolled in a single arm Phase II prospective clinical trial (NCT03867578). During the exploratory phase, MRI scans obtained from the first 5 patients were used to optimize coil positions, sequence parameters and contrast timing. Novel elements of our finalized MRI protocol included: double dose injection of Dotarem; pre-contrast free breathing HR coronal T2 weighted sequences without fat suppression; and 3D T1 HR coronal sequences, acquired in 3 breath holds at multiple post-contrast time points (range 2-18 minutes) using mDixon technique and focused on the right diaphragm/liver dome. Sensitivity was assessed by a blinded radiologist on the remaining cohort.

Results: Ten patients (out of planned 21) with MPM (7 males, median age 57 (range 43-67) years, median BMI 30.4 (range 23.9-38.9) kg/m2) were enrolled between 2/2019-9/2019. MRI was performed 3 (range 1-17) days before laparoscopic (n=6) or open (n=4) surgery. The median intraoperative peritoneal cancer index score was 34 (range 9-39). One patient was excluded from the analysis due to failed laparoscopy. Review by a blinded radiologist yielded a per-region sensitivity of 8/9 (89%) for the right diaphragm region and 6/6 (100%) for the pelvis. During the study period, no procedure-related or contrast-related adverse events were reported.

Conclusions: Our HR MRI protocol is tolerable, safe and may increase the diagnostic sensitivity of MPM detection.