Irreversible Electroporation as a Treatment for Hilar Renal Cell Carcinoma Adjacent to the Colon and Inferior Vena Cava

Abstract: A 54-year-old female presented with an incidentally discovered 2.9 cm renal cell carcinoma centered near the hilum of the right kidney and in close proximity to the colon and inferior vena cava. Given its anatomical position, irreversible electroporation was chosen to successfully ablate the mass with follow-up at 10 months demonstrating complete resolution of the lesion. 

Key words: irreversible electroporation, interventional oncology, renal cell carcinoma

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Current management options for T1a renal malignancies include partial nephrectomy and thermal ablation.^1,2 Although similar efficacy has been reported with both treatments, percutaneous thermal ablation in the kidney may be challenging or limited by close proximity to critical nontarget anatomical structures such as the collecting system, ureter, bowel, or larger arteries and veins.³ Such features may pose a risk for damage to these critical structures or heighten risk of an incomplete ablation margin. The purpose of this report is to describe the application of irreversible electroporation (IRE), a form of nonthermal ablation, to treat a T1a renal cell carcinoma situated in a position less suitable for thermal ablative methods.    

Case Report

A 54-year-old female presented with an incidentally discovered right renal mass that had grown 5 mm on computed tomography (CT) over 18 months, suspicious for a renal cell carcinoma (RCC). This enhancing mass measured 2.9 cm x 2.7 cm and was situated centrally near the hilum of the kidney, abutting both the colon and inferior vena cava (IVC) (Figure 1). Computed-tomography–guided biopsy of the mass was initially performed, confirming papillary type RCC. 

The treatment strategy for this tumor included intra-arterial injection of lipiodol with IRE the next day, given the tumor’s proximity to the IVC, renal vein, and large bowel. Lipiodol administration was performed to precisely localize the tumor for accurate probe placement. On the day of IRE, the patient was brought to the CT intervention suite where general anesthesia was administered with full muscular paralysis and cardiac synchronization. Five points of entry were determined following a diagonal configuration with 3 central probes. After prepping and draping the overlying skin in usual sterile fashion, five separate 19-gauge, 15-cm length Nanoknife (Angiodynamics) probes with 2.5 cm exposure were inserted (Figure 2). A diamond configuration pattern was determined to produce a circumferential electroporation zone that covered the tumor margin in its entirety. Two separate cycles of IRE were performed distally and proximally after pulling each probe back 1.5 cm. Pullback was performed to ensure an adequate 0.5 cm margin for ablation and entire ablation zone of 4.5 cm to 5.0 cm. A single session of electroporation using 4 cm exposure was not utilized per manufacturer recommendation regarding unpredictable ablation zones with greater exposure lengths. A current of 1,500 volts per cm was used with pulses lasting 90 microseconds. Completion CT images demonstrated iatrogenic gas collection within the lesion, an expected postprocedural finding. No procedure-related hemorrhage or other immediate complication was seen. The patient was discharged the next day after 23 hours of observation. 

Follow-up was performed with dedicated renal protocol CT scans at 1 month, 4 months, and 10 months post procedure. No residual or recurrent tumor was seen on any scan with progressive decrease in size of the lesion identified at 4 months and complete resolution of tumor at 10 months (Figure 3). Additionally, no change in baseline creatinine or hemoglobin/hematocrit levels was observed at scheduled follow-ups. 

Discussion

Irreversible electroporation is a nonthermal method of ablation that relies on the principle of using high-power direct current to generate an electrical field with quick pulses lasting approximately 70-90 microseconds at a time. These pulses result in increased cell membrane permeability, ultimately leading to cell death by apoptosis. One unique advantage of IRE is its ability to avoid damage to blood vessels, nerves, and collagenous tissue by using only short bursts of electrical energy, which prevent accumulation of heat and damage to these tissues over time. Irreversible electroporation also allows for a more complete ablation margin in those lesions abutting large blood vessels, as thermal techniques are limited by heat-sink effect in these scenarios. 

Irreversible electroporation of small T1a renal tumors has recently been reported to be safe with positive short-term clinical results. In a study by Trimmer et al, 20 patients with average tumor size of 2.2 cm who were treated with IRE had no major complication and early response rates similar to that of cryo- and radiofrequency ablation.⁴ The study, however, was limited by selection bias for smaller peripheral tumors that are often considered safer to treat due to distance from critical structures. The current case demonstrated the application of IRE to treat a slightly larger (2.9 cm) and more centrally located renal tumor adjacent the IVC, renal vein, and colon. These features would increase risk for complication and/or incomplete ablation given its proximity to these structures. Irreversible electroporation possessed a distinct advantage in this instance as the heat-sink effect of the large caliber IVC and renal vein was negated using IRE’s nonthermal technology. Irreversible electroporation was also ideal because damage to these vessels and the colon was minimized. Additionally, achieving a complete ablation with other thermal ablation methods in this case was considered difficult as it would have required very precise probe placement and adjunct methods such as hydrodissection to displace the adjacent bowel. In this case, a satisfactory technical result with mid-term clinical success was achieved using IRE, as evidenced by a complete ablation without injury to the nearby structures or signs of recurrence at 10 months follow-up. 

In conclusion, IRE may be a useful method for treating renal tumors larger than previously reported, particularly lesions in close proximity to vital structures that would otherwise be limited with the use of standard thermal based ablative methods. Moving forward, the results of this report indicate that further investigation into the safety and long-term clinical effectiveness of IRE technology for treating such tumors is warranted.  

References

1. Katsanos K, Mailli L, Krokidis M, McGrath A, Sabharwal T, Adam A. Systematic review and meta-analysis of thermal ablation versus surgical nephrectomy for small renal tumours. Cardiovasc Intervent Radiol. 2014;37(2):427-437.
2. Weight CJ, Larson BT, Fergany AF, et al. Nephrectomy induced chronic renal insufficiency is associated with increased risk of cardiovascular death and death from any cause in patients with localized cT1b renal masses. J Urol. 2010;183(4):1317-1323.
3. Dupuy DE, Goldberg SN. Image-guided radiofrequency tumor ablation: challenges and opportunities --part II. J Vasc Interv Radiol. 2001;12(10):1135-1148.
4. Trimmer CK, Khosla A, Morgan M, Stephenson SL, Ozayar A, Cadeddu JA. Minimally invasive percutaneous treatment of small renal tumors with irreversible electroporation: a single-center experience. J Vasc Interv Radiol. 2015;26(10):1465-1471.

Editor’s note: The authors have completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. Dr. Arslan reports consultancy to Penumbra and Medtronic/Covidien, and honoraria from Covidien/Medtronic, W.L. Gore, BTG, Penumbra, Bard, Cook, and Guerbet. Dr. Ahmed and Dr. Masrani report no related disclosures.

Manuscript received January 19, 2016; provisional acceptance given February 7, 2016; manuscript accepted March 15, 2016.

Address for correspondence: Osman Ahmed, MD, Vascular & Interventional Radiology, Rush University Medical Center, 1653 W Congress Pkwy, Chicago, IL 60612, USA. Email: osman1423@gmail.com.

Suggested citation: Ahmed O, Masrani A, MD, Arslan B. Irreversible electroporation as a treatment for hilar renal cell carcinoma adjacent to the colon and inferior vena cava. Intervent Oncol 360. 2016;4(4):E65-E69.