In vivo microwave‐induced porcine kidney thermoablation: results and perspectives from a pilot study of a new probe

Abstract

thermoablations overall. The kidneys were then surgically removed, and necrotic lesions measured and evaluated microscopically. The sphericity index (SI) was also calculated to evaluate lesion reproducibility. Areas of renal tissue that were missed were then microscopically evaluated by NADH in vivo staining. RESULTSIn all, 32 thermoablations were applied; the mean ( SD ) lesion diameter ranged from 1.2 (0.3) to 4.2 (0.1) cm and changed in relation to both power and time of exposure. The 50-W power particularly induced necrotic renal lesions ranging from 1.9 (0.2) to 4.2 (0.1) cm as a function of the time of exposure and the optimal SI (1.04). Pathological evaluation showed no skipped areas in the context of the lesion, or healthy kidney tissue damage close to necrotic lesions. CONCLUSIONSThermoablation with the Amica probe is safe and showed excellent in vivo effects in this porcine model. Increasing the exposure time at 50 W power could be a useful percutaneous minimally invasive treatment for small solid masses ( < 4.2 cm), avoiding the risk of missing tumour areas or kidney parenchymal damage from microwave treatment.

Microwave-induced thermoablation with Amica-probe is a safe and reproducible method to treat solid renal masses: Results from a phase I study

“…The mean age-adjusted Charlson comorbidity index was 4.8 (range, 3-7). The mean RENAL score was 9.4 (range, [8][9][10][11][12]. Table I shows the clinical and laboratory characteristics of enrolled patients.…”

“…Our previous study on porcine kidney (8) demonstrated that a standardized method of microwave administration could be obtained by using pre-determined independent variables such as power of treatment and time of exposure to energy. The Amica-probe antenna is a new refrigerated probe able to determine approximately spherical lesions with a maximum of 2.7±0.3 cm in the animal kidney tissue by an exposure time of 5 min and 50 W power (8). The best results could be obtained by using 15 min of time exposure and 50 W power with induced-lesion SI ~1.0 and diameters from 4.1 to 4.2 cm (±0.1).…”

“…We previously studied the in vivo effects of MWTA on porcine kidney, proving that MWTA is a safe and effective procedure. In particular, we demonstrated the absence of viable cells inside the ablation volume and the absence of any damage to the renal parenchyma outside it (8 (10). In brief, standardized points (1-3 points/ descriptor) were assigned based on tumor size, endophytic/ exophytic properties, nearness to collecting system and lesion location relative to polar lines.…”

“…For each patient, 50 W microwave power was delivered into the renal tissue for 5 min. The selection of power and time of exposure to MWTA was determined on the basis of previous studies on porcine kidney where these two parameters were standardized to obtain spheroidal shaped repeteable lesions (8). The probe was removed, the renal blood vessels were promptly legated and the surgeon proceeded to classic radical nephrectomy.…”

“…Pathologist thus provided for tumor and lesion measurements and tissues were stored in formalin for subsequent staining with haematoxylin and eosin (H&E) and microscopical analysis. Pathological evaluation was carried out by one dedicated pathologist in each center, in accordance with Bartoletti et al (8). All samples were analyzed to evaluate the effect of microwave energy delivered to renal tissue (no skipping) and the effect of energy on the collecting system or peritumoral healthy renal tissue, as previously described (8).…”