Computed tomography findings after radiofrequency ablation in locally advanced pancreatic cancer

Abstract

Purpose: The purpose of the study was to provide a systematic evaluation of the computed tomography(CT) findings after radiofrequency ablation (RFA) in locally advanced pancreatic cancer(LAPC).

Methods: Eighteen patients with intra-operative RFA-treated LAPC were included in a prospective case series. All CT-scans performed prior to RFA and 1 week and 3 months of post-RFA, according to standard regimen, were assessed by two radiologists in consensus, using standardized radiological scoring lists.

Results: 51 CT-scans were assessed. One week after RFA, the ablation zone was visible in all patients as a (partially) sharply defined (83%), heterogeneous area (94%). At 3 months of follow-up, the ablation zone was completely invaded by tumor in 67% of patients and still present, but decreased in 33%. In two patients (11%), local thrombosis and/or occlusion of the superior mesenteric vein occurred. The occlusions persisted without clinical consequences and the thrombosis disappeared. A peripancreatic fluid collection was visible 1 week after RFA in 3 patients, wherein the ablation zone extended ventrally outside of the pancreas.

Conclusions: Directly after RFA for LAPC, a well-defined ablation zone is visible on CT-imaging. This ablation zone is usually replaced by tumor ingrowth after 3 months. Moreover, the ablation zone regularly included vascular structures, with rare asymptomatic venous occlusion or thrombosis and without adverse effects on arteries.

Keywords: Computed tomography; Imaging findings; Locally advanced pancreatic cancer; Radiofrequency ablation.

Fig. 1

CT-images in the axial plane, of a 74-year-old woman with A a ductal adenocarcinoma in the head of the pancreas (arrow) on the pre-RFA scan, showing 90°–180° circumferential involvement of the superior mesenteric artery. B One-week post RFA, a sharply demarcated ablation zone is visible as a heterogeneous area (arrow). Moreover, the ablation zone extends ventrally outside the pancreas contour and a fluid collection is present in the transverse mesocolon. C Tumor replacing the ablation zone (arrow) at 3 months post-RFA. Note the inhomogeneous enhancement, the mass effect and the increasing size and involvement of the vessels over time

Fig. 2

CT-images in the axial plane, of a 56-year-old man with A a ductal adenocarcinoma in the head of the pancreas (arrow) of 3.4 cm transversal on the pre-RFA scan. B and C On CT 1-week post-RFA, the ablation zone included the entire tumor (arrow). C The ablation zone included the ventral contour of the pancreas (left arrow) with an accompanying fluid collection in the lesser sac (right arrow)

Fig. 3

CT-images in the coronal plane, of the same patient as Fig. 6. A The superior mesenteric vein is already narrow on the pre-RFA imaging (arrow). B One week after RFA, the SMV is occluded for the part that is embedded in the ablation zone (arrow)

Fig. 4

CT-images in the coronal plane, of a 66-year-old woman with a ductal adenocarcinoma in the head, neck and corpus of the pancreas. A The CT-image pre-RFA, shows a superior mesenteric vein (SMV) circumferential involvement of > 270°, with a pre-existent lumen reduction of > 50% (arrow) and B no thrombus present (arrow). C On the CT-image 1-week post-RFA the SMV and portal vein are occluded within the ablation zone and D a local thrombus is present in the SMV (arrow)

Fig. 5

CT-image in the coronal plane, 1-week post-RFA, of a 68-year-old woman with a ductal adenocarcinoma located in the head and neck of the pancreas, showing a thrombus in the ileocolic vein (green arrow), resulting in edema of the ascending colon (red arrows)

Fig. 6

CT-images in the axial plane, of a 44-year-old woman with a ductal adenocarcinoma in the head of the pancreas. A On the pre-RFA CT-image, the superior mesenteric artery (SMA) was involved in the tumor, with a circumferential involvement of > 270, with normal patency and without anatomical changes. B On the CT-image 1-week post-RFA, the SMA was included in the ablation zone for 90°–180°, without the occurrence of anatomical changes

Fig. 7

CT-images in the axial plane, of a 76-year-old woman with a ductal adenocarcinoma in the pancreatic corpus. A The splenic artery is encased by the tumor but still patent(arrow). B One week after RFA, the splenic artery is in contact with the ablation zone, but still patent (arrow). C This remained unchanged at follow-up 1 month later (arrow)

Fig. 8

CT-images in the axial plane, of a 51-year-old man with a ductal adenocarcinoma in the corpus of the pancreas. A On the CT-imaging before RFA, the coeliac trunk and hepatic artery are closely related to the tumor. B One week after the procedure, these arteries are constricted but still patent (arrow). C This remained stable during follow-up 3 months later (arrow)