Percutaneous Approach to Irreversible Electroporation of the Pancreas: Miami Protocol

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Despite advances in the treatment of unresectable locally advanced pancreatic cancer, outcomes remain poor. Irreversible electroporation is a nonthermal ablative modality whose role in the management of locally advanced pancreatic cancer is being studied. This review highlights patient selection, preparation, and follow-up as well as discusses the techniques to achieve safe and effective tumor ablation in this challenging location.

Section snippets

Background

Pancreatic adenocarcinoma incidence continues to increase with an estimated 46,420 new cases expected to occur in the United States in 2014.1 The most common risk factor is cigarette smoking but others include family history of pancreatic cancer, history of chronic pancreatitis, diabetes, and obesity. Treatment options include surgery, chemotherapy, and radiation therapy, but are seldom curative. Unfortunately, less than 20% of patients are anatomically resectable on presentation. Approximately

Indications

IRE in the pancreas can be applied in patients who have undergone multiple lines of chemotherapy and radiation, where the goal of care is to control local disease in the pancreas. It can also be performed in the setting of LAPC or low-volume metastatic disease that has been stable over time. In patients with borderline resectable or unresectable LAPC, IRE may downsize tumor to allow resection.18 In patients who have undergone resection, local recurrence may be managed with IRE.

Contraindications

Patients with cardiac arrhythmias cannot undergo IRE as the electrical pulses cannot by synchronized with the cardiac R waves, increasing risk for ventricular arrhythmias. Other contraindications include unsafe access for a percutaneous approach such as overlying colon obscuring the window or varices in the approach to the lesion. Gastric varices can bleed profusely and prescreening imaging should be evaluated to identify this risk. Finally, patients with uncorrectable coagulopathy and those

Patient Evaluation

Cases are reviewed in a multidisciplinary tumor board with interventional radiologists, medical oncologists, radiation oncologists, and surgeons to determine eligibility. Patients are then evaluated in the interventional oncology clinic to complete the preprocedure workup. All patients are informed that this is an off-label use of the technology.

Performance status is documented using the Eastern cooperative oncology group criteria. A performance status greater than 2 indicates poor prognosis

Special Considerations

IRE can be performed safely in peribiliary tumors.20 Patients with an incompetent ampulla from a stent or resection from a Whipple procedure are at increased risk of infection and require extended antibiotic coverage. All patients receive bowel preparation similar to a colonoscopy to decrease risk of infection and decrease the chance of colon obscuring the pancreatic bed.

Timing of chemotherapy and the IRE procedure is coordinated with the referring oncologist to optimize bone marrow recovery

Procedure

IRE is performed under general anesthesia using CT fluoroscopic guidance. An AccuSync (Accusync Medical Research Corporation, Milford, CT) device is used to gate the patient’s electrocardiogram. This detects the increasing slope of the R wave and sends a signal to the NanoKnife (Angiodyanmics, Queensbury, New York), which fires the electrical pulse after a 0.05-second delay. The NanoKnife 19-gage monopolar probes are available in 2 lengths, 15 and 25 cm. During the procedure, defibrillator pads

Immediate Postprocedure Management

After recovery from anesthesia, the patient is admitted for observation for at least 24 hours. During this time the nasogastric (NG) tube is kept to low intermittent suction and the patient is kept in NPO (nothing by mouth). Amylase and lipase levels are checked the day after the treatment. Once normal values are documented, the NG tube can be removed and diet advanced slowly. A postprocedure hemogram and chemistry panel are evaluated to assess any complication such as hemoperitoneum or acute

Technical Challenges

The greatest challenge in the percutaneous approach is choosing the path of the probes to the pancreas given proximity to critical structures (Fig. 1). Placement of the NG tube allows administration of contrast to delineate small bowel as well as permit insufflation of the stomach to push the colon caudally. At times a lesion in the pancreas may be approached from a window through the liver or by positioning the patient in a prone position and advancing probes between the spine and kidneys.

Complications and Management

If postprocedure pain does not respond to analgesia, a noncontrast CT may be obtained to assess for complications. Younger patients with surrounding normal pancreatic tissue are at an increased risk for pancreatitis. To prevent this complication the patient is kept in NPO, and NG tube is kept to low intermittent suction until amylase and lipase levels are normal. If pancreatitis does occur, conservative management includes replacement of the NG tube, intravenous hydration, and NPO until

Imaging Follow-Up

While the patient is in NPO, a postprocedure PET/CT can be obtained the next morning when possible, to assess the ablation zone and evaluate for any progression during the workup period. This should be obtained within the first 24 hours of the procedure to decrease the false positive findings from inflammation (Fig. 3). An FDG-avid rim of activity around the ablation zone is not unexpected. Any new FDG-avid focus suggests progression of disease. This finding is discussed with the referring

Early Outcomes

Narayanan et al23 reported a retrospective review of 43 patients who underwent 50 IRE procedures using a percutaneous approach from November 2010 to January 2014. Although 41 patients (95%) had undergone prior chemotherapy, only 18 had undergone prior radiation therapy. The OS was 14.5 months (95% CI: 10.4-18.6) from the date of IRE (Fig. 4). In the 30 patients with LAPC, OS was 16.2 months (95% CI: 10.1-22.3 months) as opposed to 8.6 months (95% CI: 3.1-14.1 months) for the 13 patients with

Future Directions

Although our experience with IRE in the pancreas is encouraging, it is limited by the retrospective nature of the data. The role of IRE in the management of pancreatic cancer has to be defined with prospective trials. In a phase I study, Mansson et al24 evaluated 5 patients with unresectable LAPC, who were treated with IRE using CT and contrast-enhanced ultrasound guidance. The approach was found to be safe with a 30-day mortality of 0 and only 1 case of mild pancreatitis.24 This group’s phase

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