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

Abstract

Abstract. Microwave thermal ablation (MWTA) could be considered in the future for treating small solid renal masses. The aim of the present study was to determine both the tolerability of the new Amica-probe applicator-induced MWTA used in vivo on patients with solid renal masses and the effects of heating on renal tumors and normal renal parenchyma. Fourteen patients with renal masses eligible for open radical nephrectomy were enrolled in this phase I study. All patients underwent MWTA of renal masses during the open surgery procedure before clamping of renal vascular pedicle. The effects of MWTA on patients' coagulation and tumor/renal vasculature were investigated. The histological effects of MWTA on the tumor and intralesional vital tumor cell skipping were also evaluated. The MWTA-induced lesion diameters were measured to calculate both the overall ablation volume and the lesion sphericity index (SI). The Clavien-Dindo classification was used. In all patients the RENAL score was 9.4 (8-12) and the Charlson comorbidity index was 4.8 (3-7). MWTA-induced lesion size was 44.14 mm (±22.59). Mean SI was 1.08 (±0.2). No significant differences among coagulation clinical parameters were found. No local bleeding after MWTA treatment was reported. According to the ClavienDindo classification, there were two grade II perioperative complications due to the tumor extent but not related with the MWTA treatment. No residual vital tumor cells inside the MWTA-induced lesions were found. Telephone interview at 27.4 (±4.2) months mean follow-up did not find any long-term adverse events due to previous MWTA treatment. AmicaProbe applicator-induced MWTA is a safe and reproducible method to treat solid renal masses. IntroductionPrevalence of small solid renal masses in adult population recently increased probably due to the large number of people that daily undergo preventive diagnostic investigations such as ultrasonography and computed tomography (CT) scan for unrelated symptoms, resulting in incidental tumor detection (1). Patients' comorbidities, such as cardiovascular or respiratory diseases, could represent limiting factors for planning adequate subsequent surgical approaches although conservative laparoscopy surgery is now considered the gold standard treatment, particularly for tumors <3-4 cm (2). Minimally invasive procedures, such as cryoablation (CryA) and radiofrequency ablation (RFA), have been recently proposed by different authors as alternative methods of treatment to conservative surgery with satisfactory results in terms of perioperative complications such as hemorrhage episodes or metabolic problems related to prolonged period of general anaesthesia (3). Some doubts remain on the efficacy of these methods on tumor complete eradication due to the high prevalence of tumor local recurrences due to persistent vital tumor cells in the context of the ablated tissue (tumor skipping) (4). Both CryA and RFA are based on the application of physical means (cold and heat respectively) at the centre of the lesion to induce...

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“…It has been evaluated mainly in phase I studies with promising initial results. 64 A small phase II study showed complete tumour necrosis and no complications in 12 patients. 65…”

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Microwave ablation of renal tumors: state of the art and development trends

“…Studies conducted in rabbits that previously had tumor implantation show that percutaneous microwave ablation can achieve results similar to those of open nephrectomy having thus the potential of being a nephron salvaging treatment for small renal tumors [23]. However, microwaves have some limitations in particular in relation to the design of the antenna that does not allow a complete control of the lesion during the ablation with an oval shape of coagulation [24,25].…”

“…Histochemical examinations revealed no cell death beyond the ablation area: this is particularly important in renal ablation to preserve healthy parenchyma and, above all, vascular and caliceal structures [28]. In the following year, Bartoletti et al [23] published another phase I study with the aim to determine the tolerability of the Amica-probe in vivo in patients with solid renal masses and the effects of heating on renal tumors and normal renal parenchyma. No local bleeding after treatment was reported showing the reduced risk of bleeding of MWA [23].…”

“…In the following year, Bartoletti et al [23] published another phase I study with the aim to determine the tolerability of the Amica-probe in vivo in patients with solid renal masses and the effects of heating on renal tumors and normal renal parenchyma. No local bleeding after treatment was reported showing the reduced risk of bleeding of MWA [23]. The results of these studies described have been summarized in Table 1.…”