Rajesh Gupta MD, Presenter: Nothing to Disclose

Elham Safaie MD, Abstract Co-Author: Nothing to Disclose

Robert Matthews MD, Abstract Co-Author: Nothing to Disclose

Matthew A. Barish MD, Abstract Co-Author: Stockholder, Blackford Analysis Ltd

Dinko Franceschi MD, Abstract Co-Author: Nothing to Disclose

Roberto Bergamaschi MD, PhD, Abstract Co-Author: Nothing to Disclose

To correlate FDG PET-CT findings with pelvic MRI and fusion imaging to assess metastatic extent in rectal cancer patients. 

Initially, we performed a retrospective chart review of rectal cancer patients at our institution from June 2008 to March 2013. We identified 18 patients, 11 males and 7 females with an average age of 58 years that had initial staging FDG PET-CT and pelvic MRI obtained within a 3 month interval. These patients were initially staged by pelvic MRI and confirmed with histology when available. The staging ranged from I to III. We compared PET-CT and MRI findings to assess tumor extent, local and distant metastases. We then fused PET and pelvic MRI to assess nodal involvement using MIM fusion software. 

A total of 5 patients (28%) were upstaged based on hypermetabolic lesions seen on PET-CT. Three patients went from stage III to IV. The first had metastases to distant lymph nodes, the second had hepatic metastases and the third had local metastases to common iliac nodes. PET-CT upstaged one patient from II to IV as retroperitoneal and paraaortic nodes were identified, and one another patient upstaged from I to IV due to a lung metastasis. A total of 4 patients (22%) were downstaged because lymph nodes identified on MRI were negative on PET. Three patients went from stage III to I. Two patients had perirectal lymph nodes on MRI that were negative on histology and not FDG-avid, and the third patient had perirectal nodes on MRI that were not FDG-avid. An additional patient was downstaged from III to II as MRI and histology discovered several sigmoid mesentery nodes that were not FDG-avid. MRI and FDG PET-CT examinations were concordant in the remaining 50% of the patients. Fusion PET-MRI found additional hypermetabolic nodes in 2 patients. One had an external iliac node and another had perirectal nodes that were not clearly identified on PET-CT. 

MRI provides excellent anatomical evaluation of tumor size and extent, while, PET-CT provides additional information on metabolic activity. Fusion PET-MRI can provide more accurate staging of local nodal involvement. This may change the initial stage which can affect treatment options. 

Both FDG PET-CT and pelvic MRI are standard of care for staging and restaging rectal cancer patients, however, fusion PET-MRI can provide a more accurate assessment of local disease extension. 

Gupta, R, Safaie, E, Matthews, R, Barish, M, Franceschi, D, Bergamaschi, R, Correlation of FDG PET-CT with Pelvic MRI in Staging of Patients with Rectal Cancer Using Fusion PET-MRI.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14014345.html