Matteo Cappucci MD, Presenter: Nothing to Disclose

Marco Di Girolamo MD, Abstract Co-Author: Nothing to Disclose

Vincenzo David MD, Abstract Co-Author: Nothing to Disclose

Daniela Prosperi, Abstract Co-Author: Nothing to Disclose

Stefania Durante, Abstract Co-Author: Nothing to Disclose

Elsa Iannicelli MD, Abstract Co-Author: Nothing to Disclose

In case of suspicion of locally recurrent rectal cancer, the use of MRI with diffusion-weighted MRI or [18F]-fluorodeoxyglucose (FDG) PET/CT still remains debated. Our purpose was to compare the two imaging modalities in the discrimination between local recurrence and post-treatment scar tissue.

Since september 2010, all patients treated with neo-adiuvant chemio-radiation therapy and surgical resection for rectal cancer were referred, in case of high suspicion of local recurrence during  follow-up, for MRI and PET/CT.25 patients were enrolled (17M, 8F; mean age: 64) and the mean time of the diagnostic evaluation after surgical resection was 14 months. MRI was performed with 1,5T superconductice magnet with TSE T2-w. scan on sagittal, axial and coronal planes, DWI axial scans (b values:50,400,800) and post-contrast fat saturated Flash 2D T1-w. axial scans. All exams were reported by two radiologists in consensus. Total-body PET/CT images were aquired 60 minutes after i.v. injection of 185 MBq FDG and reported by two physicians  who were unaware of MRI findings. In case of concordantly negative findings, the patients followed a routinary follow-up. Patients with concordantly positive findings or discordance were subjected to a CT-guided biopsy or surgical excision for histological evaluation.

MRI+DWI and PET/CT were concordantly negative in 15pts and concordantly suggestive of recurrence in 7pts. The patients with concordantly findings of fibrosis remained disease-free after 10 months follow-up. In 6pts the concordantly imaging suggestion of recurrence was confirmed by biopsy while in one patient hystology disconfirmed the suspected diagnosis. A discordance with negative MRI+DWI and positive PET-CT was found in 3 cases: in 2pts the histological speciment was negative (2 PET/CT false positive) while in 1 patient a recurrence was found at biopsy (MRI+DWI false negative). The sensitivity, specificity and diagnostic accuracy of MRI+DWI was respectively 86%, 94% and 92% while for PET/CT was 100%, 83% and 88%

MRI+DWI shows higher specificity than PET/CT, especially in case of active inflamatory tissue while PET/CT has a higher sensitivity than MRI+DWI and can detect distant metastasis. MRI is also essential in the local recurrence surgical planning.

MRI with DWI shows higher specificity than PET/TC in the evaluation of suspected local recurrence rectal cancer and it is recommended.

Cappucci, M, Di Girolamo, M, David, V, Prosperi, D, Durante, S, Iannicelli, E, MRI with DWI Compared with FDG-PET/CT in the Evaluation of Suspected Local Recurrence in Rectal Cancer.  Radiological Society of North America 2013 Scientific Assembly and Annual Meeting, December 1 - December 6, 2013 ,Chicago IL. http://archive.rsna.org/2013/13020109.html