MR imaging can non-invasively and accurately show small peritoneal tumors that are invisible on other imaging tests such as CT or PET. While CT and PET often miss small but important peritoneal tumors, MRI routinely shows small tumors only a few millimeters in size. MRI achieves this remarkable accuracy without using any radiation making it a safer, more accurate, and less expensive alternative to CT.
Our longstanding interest in using MRI to evaluate patients with peritoneal tumor stems from a close collaboration between radiology and surgical oncology. This exchange of knowledge and ideas between Dr. Russell Low and Dr. Robert Barone has allowed us to devise and perfect imaging techniques for peritoneal disease that are truly unique and trend setting.
Our MRI approach to peritoneal tumor involves using gadolinium-enhanced imaging to show enhancing peritoneal tumors. We also rely on diffusion weighted MR imaging (DWI) as these tumor often light-up on diffusion imaging. Patient preparation involves distending the small bowel and colon with water soluble contrast for optimal imaging.
The clinical uses for peritoneal MRI include essentially any patient with abdominal malignancy, including ovarian cancer, colon cancer, pancreatic cancer, gastric cancer, primary peritoneal tumor, and appendiceal cancer. The ability of MRI to show subtle peritoneal tumors can provide your oncologist or surgeon with vital information that can help lead to the correct diagnosis and optimal management.
For example, in patients with appendiceal cancer MR imaging for preoperative assessment prior to CRS and HIPEC may improve patient selection and preoperative planning. We have found that MRI can accurately predict the surgical PCI score and can be used to stratify patients into those with small volume (PCI score <10), moderate volume (PCI score 11-20), and large volume (PCI score >20) intraperitoneal tumor. Combined with the histological grade of the tumor the MRI PCI score can be used to select patients who are more likely to achieve a complete surgical cytoreduction with less morbidity. Non invasive DPAM tumors can be successfully surgically cytoreduced even with large volume tumor.
The early detection of recurrent tumor on serial laboratory tests and imaging studies plays a critical role in identifying patients who should be considered for repeat CRS and HIPEC. While CT scanning is commonly used to image patients with appendiceal cancer its limitations for showing small peritoneal tumors is well documented. MR imaging has inherently superior contrast which allows it to depict small peritoneal tumors more effectively. At our institution we have been using MRI in patients with appendiceal cancer for preoperative staging and for surveillance following CRS and HIPEC.
Imaging studies can play an important role in monitoring patients following CRS and HIPEC. However, the limitations of CT in patients with peritoneal carcinomatosis are well understood. Koh et al confirmed that CT significantly underestimated intraoperative PCI detecting only 11% of peritoneal tumors <0.5 cm compared to 95% of tumors larger than 5 cm. In a multi-institutional study Esquivel et al found that the preoperative CT PCI score underestimated the extent of carcinomatosis in 33% of patients. The poor sensitivity of CT for detecting small peritoneal tumors limits its accuracy in determining a patient’s preoperative PCI score and in detecting recurrence following CRS and HIPEC. Concerns about the cumulative radiation doses from repeat CT scans also favor the use of MRI for surveillance. The amount of radiation from a single CT scan is equivalent to the radiation exposure from hundreds of chest xrays!
We believe that dedicated Peritoneal MRI should be used for all patients with known or suspected peritoneal tumors. The accuracy of MRI for showing tumors of the peritoneum is superior to CT and PET and makes it the examination of choice.
References:
1. Low RN, Barone RM. Combined Diffusion-Weighted and Gadolinium-Enhanced MR Imaging Can Accurately Predict the Peritoneal Cancer Index (PCI) Preoperatively in Patients Being Considered for Cytoreductive Surgical Procedures. Ann. Surg Oncol 2012;19:1394–1401.
2. Low RN, Barone RM, Gurney JM. Mucinous appendiceal neoplasms: preoperative MR staging and classification compared with surgical and histopathologic findings. Am. J. Roentgenol 2008;190:656–665.
3. Low RN, Sebrechts CP, Barone RM, Muller W. Diffusion-Weighted MRI of Peritoneal Tumors: Comparison with Conventional MRI and Surgical and Histopathologic Findings--A Feasibility Study. Am. J. Roentgenol 2009;193:461–470.
4. Koh JL, Tan TD, Glenn D, Morris DL. Evaluation of preoperative computed tomography in estimating peritoneal cancer index in colorectal peritoneal carcinomatosis. Ann Surg Oncol. 2009;16:327–333.
5. Esquivel J, Chua TC, Stojadinovic A, Melero JT, Levine EA, Gutman M, Howard R, Piso P, Nissan A, Gomez-Portilla A, Gonzalez-Bayon L, Gonzalez-Moreno S, Shen P, Stewart JH, Sugarbaker PH, Barone RM, Hoefer R, Morris DL, Sardi A, Sticca RP. Accuracy and clinical relevance of computed tomography scan interpretation of peritoneal cancer index in colorectal cancer peritoneal carcinomatosis: a multi-institutional study. J Surg Oncol. 2010;102:565–570.
