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Introduction IRE is a novel technique, which delivers localized electric current using peri-tumoral probes causing irreversible cell membrane damage and cell death. Due to its non-thermal action, it is ideally suited for tumors with vascular invasion. This study was designed to evaluate the safety and efficacy of IRE in peri-vascular tumors.
Methods Analysis of 107 consecutive patients over 7 institutions with tumoral vascular invasion (defined as <5mm from major vessel) was done from a prospective multi-institutional registry. Safety parameters, complications and efficacy were evaluated. Patients without follow-up or those unfit for general anesthesia were excluded.
Results A total of 117 procedures were performed for 84 pancreatic and 17 liver lesions among others. Majority had prior chemotherapy (82,76.7%) or local treatment such as radiation 47(44%), other ablations (11,10.2%) or embolization therapy (10,9.3%). Percutaneous access for IRE was used in 32(27%) patients while laparotomy access was used in 81(69%). Concurrent major abdominal procedures were performed in 56(61%). Vascular invasion was either to the portal vein(n=82), hepatic vein(n=6), SMA/SMV(n=24) or celiac axis(n=6). Procedure time (Median 170 mins) was significantly higher in patients with concurrent major surgery (195 vs. 114 minutes, p<0.000). Per patient, median 2 lesions of 3.5 cm target size and tumor size of 3x2x2.75 cm were ablated. Overall Morbidity rate was 36.7%, attributable complication rate was 16.2% and high-grade (>Grade 3) complication rate was 5.1%. Three vascular complications (SMV, portal vein and Hepatic artery thrombus) and 2 peri-procedure deaths (one unrelated) were seen. Diabetes (p=0.05), pancreatic lesions (p<0.001), prior radiation (p=0.01) and concurrent major procedures (p=0.02) were associated risk factors. Incomplete ablation was seen in 7(6%) patients. Median follow up was 12 months with LRFS was 9.2 months. Conclusion This is the largest study of any interstitial ablation in tumors with vascular invasion. The low vascular and IRE-related complication rates high ablation rate demonstrates IRE's safety efficacy in these locally advanced tumors with vascular invasion.
Lesion with vascular invasion: distribution, characteristics and complications

	Complications	High-Grade Complications	P value#
Liver (17)	3 (17.6%)	2 (11.7%)	0.2/0.3
Pancreas (84)	37 (44%)	17 (20.2%)	0.007/0.2
CRHM* (11)	0	0	0.01/0.02
Pancreatic adenocarcinoma (76)	38 (50%)	16 (21%)	<0.000/ 0.1
Laparotomy Access (81)	39 (48.1%)	20 (24.7%)	<0.000/0.002
Percutaneous access(33)	3 (9%)	1 (3%)	<0.000/0.005 (lower CR) *
Concurrent major abdominal procedure (56)	27 (48%)	13 (23%)	0.02/0.07
Target Size (yes vs. no, cm)	3.8 vs. 3.5	3.65 vs. 3.6	0.1
Length of stay (yes vs. no, Days)	10.6 vs. 4.7	15 vs. 5.4	<0.000/<0.000
PMH Diabetes (20)	13 (65%)	7 (35%)	0.009/0.05
Radiation (47)	24 (51%)	12 (25.5%)	0.01/0.1
Prior Ablation/ resection (17)	1 (5.2%)	0	0.01/ 0.002

# p value significant <0.05 CR Complication rate CRHM Colorectal Hepatic metastasis