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Purpose: Irreversible electroporation (IRE) is a nonthermal ablative technique that has potential safety advantages over thermal ablation in the treatment of tumors near critical structures. It creates an electrical field which forms permanent nanopores in the membranes of cells and triggers apoptosis. This case series reviews three patients with pelvic metastases from colorectal cancer treated with IRE.

Material and Methods: Two patients had rectal cancer and one sigmoid colon cancer. The mean age was 55 years and there were two males and one female. Thermal ablation was contraindicated due to proximity to ureter, bladder, bowel, and/or sciatic or lumbosacral nerves. Every patient was referred to interventional radiology due to progression after primary tumor resection, FOLFOX chemotherapy, and pelvic radiation. All patients were treated with NanoKnife IRE (AngioDynamics, Latham, New York).

Results: To reduce IRE risk, hydrodissection was performed. In each case, either four or five IRE probes were used with up to two pull back treatments. Probe exposure length was either 1.5 cm or 1 cm. One patient had no recurrence after last follow-up at 23 months. Two patients had recurrence, one after 6 months (retreated with IRE) and the other after 17 months. Complications included partially reversible lower extremity sensory and motor deficits, contained colon perforation, and ureteral injury requiring stent placement.

Conclusions: IRE is a promising tool for local treatment of recurrent pelvic metastases when other local treatments are contraindicated. IRE leaves supporting tissue largely unaffected, so that blood vessels and intestines are relatively preserved, and damaged axons may regenerate. This is important in the pelvis where sensitive structures include bladder, ureters, bowel, lumbar and sacral nerve roots, and the sciatic nerve. For these patients, IRE was selected over thermal ablation due to decreased risk of complications. Complete ablation is possible for smaller lesions, while symptom control should be the focus of larger lesions.

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