Posted in North America, Research

Role of imaging in the applicability of irreversible electroporation for the management of pancreatic adenocarcinoma

 March 18, 2023

. 2023 Jan-Feb;56(1):42-49.


doi: 10.1590/0100-3984.2022.0032-en.

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Thiago Pereira Fernandes da Silva et al.


Radiol Bras.


2023 Jan-Feb.

Pancreatic ductal adenocarcinoma is one of the most aggressive malignant neoplasms, with a one-year survival rate below 20%. Axial methods (computed tomography and magnetic resonance imaging) play a fundamental role in the diagnosis and staging of the disease, because they provide adequate anatomical resolution in the assessment of key structures, mainly vascular structures. Pancreatic ductal adenocarcinoma is most often discovered in advanced stages, when surgical resection is no longer feasible. In that scenario, minimally invasive treatment alternatives have been developed in attempts to change the natural history of the disease. Irreversible electroporation, an interventional procedure that minimizes deleterious effects on adjacent tissues, has proven useful for the treatment of tumors traditionally considered unresectable. Despite the growing acknowledgment of this technique as a tool for the management of pancreatic ductal adenocarcinoma, it is still relatively unknown among radiologists. In this study, we sought to provide an overview of the main characteristics and eligibility criteria that must be considered for the indication of irreversible electroporation in cases of pancreatic ductal adenocarcinoma.

O adenocarcinoma ductal de pâncreas é uma das neoplasias malignas mais agressivas, com taxas de sobrevivência anuais inferiores a 20%. Os métodos axiais (tomografia computadorizada e ressonância magnética) têm papel fundamental no diagnóstico e estadiamento da doença, por fornecerem adequada resolução anatômica na avaliação de estruturas-chave, principalmente vasculares. O adenocarcinoma ductal de pâncreas é frequentemente descoberto em estágios avançados e sem viabilidade de ressecção cirúrgica, e nesse cenário o desenvolvimento de alternativas terapêuticas minimamente invasivas tem sido ainda mais importante para a mudança de sua história natural. A eletroporação irreversível, procedimento intervencionista que minimiza efeitos deletérios nos tecidos adjacentes, vem se destacando no tratamento de lesões tradicionalmente consideradas irressecáveis. Essa técnica, apesar de ganhar cada vez mais espaço no manejo terapêutico do adenocarcinoma ductal de pâncreas, ainda é pouco familiar aos radiologistas. Neste estudo, buscamos expor, de forma sucinta e didática, os fundamentos da técnica, as principais características de imagem e os critérios de elegibilidade que devem ser considerados para indicação da eletroporação irreversível nessa doença.


Keywords:

Carcinoma; Electroporation/methods; Magnetic resonance imaging; Pancreatic neoplasms/pathology; Tomography; X-ray computed; pancreatic ductal/pathology.

Figures


Figure 1



Figure 1

Representation of the American Joint Committee on Cancer international
system of classification of tumors(2), based on imaging assessment of the tumor (T),
lymph nodes (N), and metastases (M). (CA, celiac artery; SMA, superior
mesenteric artery; CHA, common hepatic artery).


Figure 2



Figure 2

Intraoperative IRE.


Figure 3



Figure 3

Vascular anatomy relevant to pancreatic adenocarcinoma.


Figure 4



Figure 4

Axial maximum intensity projection reconstruction of a
contrast-enhanced CT scan of the abdomen, showing a pancreatic tumor
in a 61-year-old man. There is contact (< 180°) between the tumor
and the superior mesenteric artery (SMA), with amputation of the
inferior pancreaticoduodenal artery (IPDA, first branch of the SMA).
Borderline-resectable tumor. IRE was used as an adjuvant
intraoperative technique.


Figure 5



Figure 5

Axial contrast-enhanced CT scan of the abdomen, in the arterial
phase, showing a tumor in the pancreatic body in a 78-year-old man.
A comparison between the imaging aspects of the acquisition with a
dual-energy protocol depicting the tumor in contact (> 180°) with
the celiac artery and in marginal contact with the abdominal aorta.
Unresectable tumor. The dual-energy technique increases the contrast
between different tissues by processing a set of acquisitions at
different voltages. Benefits over the conventional technique include
better differentiation between the tumor and healthy pancreatic
parenchyma, optimized vascular assessment, reduced tomographic beam
attenuation artifacts caused by metallic materials (e.g., surgical
clips and biliary stents), and improved image quality when the
acquisition is suboptimal (e.g., reduced renal or cardiac function,
which alter the circulation dynamics of iodinated contrast in the
bloodstream). IRE was performed as a stand-alone procedure.


Figure 6



Figure 6

Axial contrast-enhanced CT scan of the abdomen, in a maximum
intensity projection, showing a tumor (T) in the pancreatic body in
a 69-year-old woman, in contact (> 180°) with the celiac artery
and the common hepatic artery. Unresectable tumor. Involvement of
the splenic artery, with caliber reduction, and splenic vein
thrombosis are also observed. IRE was used as a stand-alone
procedure, in combination with chemoradiotherapy.


Figure 7



Figure 7

Axial contrast-enhanced CT scan of the abdomen (A), in the portal
phase, and axial magnetic resonance imaging scan of the abdomen (B),
in 3D T1-weighted sequence, showing a tumor (T) in the head of the
pancreas in contact (< 180°) with the spleno-mesenteric junction
in a 67-year-old woman. Note the focal tapering and irregular
contours of the tumor. Borderline-resectable tumor. IRE was
performed intraoperatively as an adjuvant procedure.


Figure 8



Figure 8

Unenhanced CT scan of the abdomen, showing an expansile tumor (T) in
the tail of the pancreas, involving the splenic artery, as well as
occluding the splenic vein and left renal vein, in an 89-year-old
woman. Resectable tumor. The patient had an unfavorable performance
status, with multiple comorbidities, and surgery was contraindicated
due to high surgical risk. As a therapeutic alternative, CT-guided
IRE was used as an exclusive procedure, in combination with
chemotherapy.


Figure 9



Figure 9

Axial contrast-enhanced CT scans of the abdomen, in the portal phase,
showing a tumor, centered in the head and uncinate process of the
pancreas, in a 69-year-old man. Note the extensive involvement of
local anatomical structures, especially the gastric wall and the
third portion of the duodenum. The tumor was also in contact (>
180°) with the superior mesenteric artery and the common hepatic
artery. There were also liver metastases. Unresectable tumor.
Involvement of hollow viscera walls represents a contraindication to
IRE (risk of perforation). In this case, it was possible to perform
CT-guided stand-alone IRE based on confirmation by endoscopic
ultrasound that the wall infiltration was segmental, with integrity
of some layers. Although duodenal or gastric involvement is not one
of the criteria of the American Joint Committee on Cancer TNM
system, evidence in the literature indicates that it is an isolated
factor with an impact on disease survival(11).


Figure 10



Figure 10

Contrast-enhanced abdominal CT scans, in the axial plane, showing a
tumor [T] in the head of the pancreas, in a 79-year-old man, with
extensive local involvement, highlighting infiltration of the second
portion of the duodenum, the common hepatic artery, and the proper
hepatic artery. Endoscopic ultrasound could facilitate the
evaluation of infiltration of the layers of the duodenal wall, which
represents a contraindication to IRE. Note also the malignant
obstruction of the bile ducts, a complication occasionally observed
in PDAC and that requires treatment with a biliary stent before IRE
can be performed, because of the risk that the edema generated by
the procedure will worsen the obstruction.


Figure 11



Figure 11

Flow chart of practices in PDAC, highlighting the role of IRE.

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