Date Published: February 28, 2018
Publisher: Springer US
Author(s): Steffi J. E. Rombouts, Tyche C. Derksen, Chung Y. Nio, Richard van Hillegersberg, Hjalmar C. van Santvoort, Marieke S. Walma, Izaak Q. Molenaar, Maarten S. van Leeuwen.
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).
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.
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.
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.
The online version of this article (10.1007/s00261-018-1519-y) contains supplementary material, which is available to authorized users.
All 18 consecutive patients were included in this radiological study, consisting predominantly of females (61%), with a median age of 64 years (IQR 52–70). 14/18 patients received no chemotherapy before or after RFA (Table 1). None of the patients received pre- or post-RFA radiation. RFA-related morbidity was 11% (2/18): one portal vein thrombosis and one duodenal injury occurred due to the procedure.Table 1CharacteristicsAll patients (n = 18)Patient characteristics Female11 (61%) Age (median [IQR])a64 (52–70) Induction chemotherapy None16 (89%) FOLFIRINOX2 (11%) Chemotherapy after RFA None14 (78%) FOLFIRINOX1 (5.6%) Gemcitabine2 (11%) FOLFIRINOX + gemcitabine1 (5.6%)Tumor characteristics Localization Head14 (78%) Corpus4 (22%)Largest diameter in mm (mean [SD]) Transversal44 (11) Coronal44 (10)Vascular involvement SMA13 (72%) Celiac trunk8 (44%) CHA12 (67%) PV13 (72%) SMV17 (94%)aAt RFA procedure; IQR, inter-quartile range; SMA, superior mesenteric artery; CHA, common hepatic artery; PV, portal vein; SMV, superior mesenteric vein
The main interest of this study was to evaluate the appearance of the ablation zone on CT, which was sharply defined 1 week after RFA for LAPC. In two patients, the tumor was no longer seen, suggesting complete ablation of the tumor. Three months after RFA, the ablation zone was no longer visible on CT-imaging in 67% of patients. Given the inhomogeneous enhancement of the replacing tissue, the obvious mass effect and the increasing size and circumferential vessel involvement over time, this appears consistent with tumor infiltration (Fig. 1C). Moreover, as the majority of patients (89%) had an incomplete ablation, this would confirm tumor infiltration even more. Additionally, tumor infiltration can also explain why the boundaries of the ablation zone became less defined over time. A potential other explanation is progression of necrosis and liquefaction of the ablated area . However, no necrosis or liquefaction was identified on the CT-images in this study by the radiologists. Furthermore, shrinkage of the ablation zone, due to amelioration of the inflammatory reaction provoked by RFA, may also decrease the diameter of the ablation zone. If the associated oedema decreases, a smaller area remains, where the oedema shortly after RFA could have been mistaken for a part of the ablation zone [13–16]. Notably, we did not have pathological proof to support one of these explanations.