The efficacy and safety of Irreversible Electroporation for the ablation of Small Renal Masses: A prospective in-vivo pilot study

The past two decades have shown a steady increase in the incidence of small
renal masses (SRM) up to 4 cm. This is in part the result of an increased use
of abdominal imaging for non-urological complaints leading to incidental renal
tumour detection. Nephron sparing surgery, in the form of partial nephrectomy,
is considered to be the gold standard for treatment of SRMs. Currently thermal
focal therapies such as cryoablation and radiofrequency ablation (RFA) are
primarily recommended in patients who are poor surgical candidates or have a
genetic predisposition for developing multiple tumours. Recent studies have
shown 5-10 year oncological follow-up of cryoablation and RFA to be slightly
inferior to partial nephrectomy, balanced by a lower complication rate.
Promising long-term results combined with little or no loss in renal function
have created interest in thermal focal therapies as a future treatment option
for a broader range of patients. Focal treatment of tumours requires precisely
dosed and accurate ablation of unwanted tissue while reserving surrounding
healthy tissue and vital structures such as blood vessels, nerves, the renal
collecting system and neighbouring organs. The unselective destruction of
thermal ablation can result in damage of vital structures in the vicinity of
the tumour. Thermal ablation intensity can be impaired due to *thermal sink*.
The vicinity of large vessels and the renal collecting system causes thermal
fluctuations leading to inconsistent ablation results.

Primary Objectives:
- To determine the clinical efficacy of IRE ablation of small renal masses (*
4cm), assessed by calculating recurrence and residual disease at follow-up,
measured through the (non-)presence of tumour enhancement on cross-sectional
imaging post IRE
Secondary Objectives:
- To determine the safety of IRE ablation of small renal masses (* 4cm), by
evaluating device and procedural adverse events using CTCAE v4.0
- To evaluate the use of CT, MRI, and CEUS in the imaging of ablation success,
extend of the ablation zone, 1 week, 3 months, 6 months, and 1 year post IRE
- To evaluate peri-operative outcomes after IRE ablation of small renal masses
(* 4cm), such as renal function, measured by creatinine levels and eGFR pre-
and post-operative, proteinuria, average length of hospital stay, average
operation time, and pain level after IRE, measured by VAS and analgesics use

This is a prospective, human, in-vivo, pilot study.

Patients will receive IRE ablation of the SRM, performed under general
anaesthesia. Follow-up will be performed using CT, MRI, and CEUS at 1 week, 3
months, 6 months, and 1 year post IRE.

Conventional focal ablative therapies, RFA and cryoablation, are indicated in
patients presenting with a solid enhancing small renal mass who are poor
surgical candidates. In this study IRE ablation will be offered to this group
of patients. Early research into renal IRE have proven the procedural safety,
and the peri-procedural burden, to be comparable to conventional ablative
therapies. The lack of long term oncological follow up poses a potential risk
as patients cannot be counselled on the risk of residual or recurrent tumour.
Post IRE follow up will be equal to post cryoablation follow up and therefore
does not pose additional burden with regard to ionizing radiation. When renal
function appears to decrease, only MRI and CEUS will be performed to prevent
kidney failure.