Management implications of FDG-PET/MR in untreated intrahepatic cholangiocarcinoma.

Objectives: Intrahepatic cholangiocarcinoma (iCCC) continues to portend a poor survival. The non-invasive staging is based on CT and MR but both modalities have intrinsic limitations and diagnostic laparoscopy is often performed at the beginning of an operation for presumed resectable iCCC. The aim of our study was compare (FDG-PET/MR) to conventional imaging to evaluate impact on the clinical management of iCCC patients.

Methods: The study retrospectively enrolled 37 patients with iCCC who underwent FDG-PET/MR in five hepatic oncology referral centers. Retrospective review of the clinicopathologic features of patients with iCCC was carried out. Conventional imaging included a combination of PET/CT and/or MR and/or CT. All patients had at least one study with radiologic contrast enhancement. Their electronic medical records were evaluated by a PET/MR clinical reader along with the referring clinician to ascertain if any change in management had been prompted by PET/MR versus conventional imaging. McNemar test was used to ascertain if the differences in management were statistically significant (P<0.05).

Results: The median age of enrolled patients was 63.5 years, 20 (54%) were female. None of the patients had received chemotherapy or radiation therapy prior to PET/MR imaging. 26 patients underwent a same day PET/CT. For the majority of patients, conventional imaging and PET/MR were concordant (26/37; 70.3%) with no change in management. Discordant results between conventional imaging and PET/MR occurred in 11/37 patients (29.7%), resulting in a change in the clinical management of the patients. For all these 11 cases, PET/MR was more accurate than conventional imaging, as confirmed by further tests, including biopsy and/or laparoscopy. This change in management relative to standard imaging resulted in cancellation of an operation in 5/37 (13.5%), permitted operative intervention in 4/37 (10.8%) and prompted a different surgical approach in 2/37 (5.4%) of patients. The cancellation of surgery was due to unresectable locally advanced disease in 3 and stage IV disease in 2. Results were confirmed by pathology or imaging on follow up. In 2 patients resectable both at PETCT and PETMR, PET/MR altered the surgical plan by demonstrating diaphragmatic infiltration in one, and metastases to segment V in the other case, that would have otherwise been left in place. These two patients underwent a different surgery approach due to PET/MR findings. The 4 patients which PET/MR permitted operative intervention were deemed unresectable by conventional imaging but PET/MR ruled out metastases, as confirmed intra-operatively. The differences in PET/MR driving management versus conventional imaging were statistically significant (P=0.002, exact McNemar test), as well in the 26 patients who had PET/CT as part of the conventional imaging tests (P=0.004, exact McNemar test). Conclusion: Accurate evaluation of the local and distant extent of iCCC has profound implications on patient management. In our study, FDG-PET/MR significantly impacted the treatment plan in almost one-third of patients with iCCC allowing a more precise assessment of the intrahepatic extent of disease as well as detecting or ruling out distant metastases. Therefore, FDG-PET/MR should be considered in the routine staging of patients with iCCC. The main limitations of our study are the small sample size. However, to the best of our knowledge this is the first study investigating PET/MR in the settings of iCCC.