Ultrasound-Guided Percutaneous Microwave Ablation of Bilateral Renal Cell Carcinoma: A Report of Eight Cases Ultrasound-Guided Percutaneous Microwave Ablation of Bilateral Renal Cell Carcinoma: A Report of Eight Cases.

Objective: We reviewed a series of 8 cases of bilateral renal cell carcinomas (RCCs) to evaluate the safety and outcomes of ultrasound-guided percutaneous microwave ablation (MWA) techniques, which is an important alternative to tumor control in localities and renal function preservation interventions. Materials and Methods: Eight patients of bilateral RCCs treated with percutaneous microwave ablation under ultrasound guidance in our department between November 2012 and October 2018 were reviewed retrospectively. The tumor diameters range from 0.7 to 6.2cm. Microwaves were emitted at 45-60W for 300 seconds and prolonged as necessary to attain temperatures sufficient to ensure tumor kill. Renal functions including serum creatinine and urea levels before MWA and one day after MWA were collected. The treatment efficacy and technical success were evaluated by contrast enhanced ultrasound and computed tomography or magnetic resonance imaging. Results: All tumors were completely ablated 2MWA sessions; 2 recurrences were observed. No severe complications occurred during MWA procedure. No significant differences in the post-MWA renal functions compared with the pre-MWA levels. The ablation zone was gradually shrank with time. Conclusion: Ultrasound guided percutaneous MWA appears to be a safe and effective technique for bilateral renal cell carcinomas. Personalized MWA can achieve good local tumor control, renal function preservation and low complication rate.


Introduction
Bilateral renal cell carcinomas (RCCs) are clinically uncommon, accounting for 1%-5% of renal cell carcinomas [1,2]. Compared to unilateral RCC, bilateral RCCs presents a surgical challenge in balancing the need for long-term tumor control and preserving maximal renal functions. The optimal management of bilateral RCC remains controversial. Given the surgical constraints, nephron-sparing surgery and image-guided thermal ablation have increasing popularity in recent years due to its safety and efficacy for bilateral RCC, patients having elder age or with comorbidities [3][4][5][6][7]. Compared with nephron-sparing surgery, image-guided thermal ablation, such as percutaneous microwave ablation (MWA), radiofrequency ablation (RFA), and cryoablation, has showed similar good effects on local tumor control, but less invasive and low incidence of major complications in the treatment of RCC [8][9][10]. MWA ablation technique directly destroy a large lesion near the antenna in a short time, and MWA energy propagation is rarely limited by tissue desiccation and charring [11]. MWA ablation techniques and devices have undergone significant improvements.
And ultrasound (US) guided percutaneous MWA is now a wellestablished technique for treating small renal tumors [10,12]. To the best of our knowledge, there have been no published reports concerning US guided percutaneous MWA ablation in the treatment of bilateral RCCs. In this study, we aimed to evaluate the safety and clinical outcomes of patients with bilateral RCCs with US guided percutaneous MWA ablation.

Imaging Examination
Before treatment, all patients were subjected to chest x-ray, abdominal ultrasonography, computed tomography (CT), and/or magnetic resonance imaging (MRI) were performed to evaluate bilateral kidneys and the existence of metastasis.

MWA Ablation Protocol
The

Follow-up
US imaging, contrast-enhanced CT or MRI was routinely employed on day1-day3 after the MWA ablation procedure to evaluate the treatment efficacy and technical success. An irregular peripheral enhancement of the ablated lesion indicated a possible residual unablated tumor; consequently, an additional MWA session was repeated within 1 week.

Statistical Analysis
The measurement data were presented as the mean ± SD and compared with Student's t-test or Mann-Whitney test where appropriate. Statistical analysis was performed using SPSS 11.0 soft ware for windows (SPSS Inc., Chicago, IL, USA). A p value less than 0.05 was considered statistically significant.

Patient Demographics
In the present study, 8 patients (7 males and 1 female; mean age 59.4 ± 9.9 years) who had bilateral RCCs were included for analysis (

Outcomes of MWA Ablation
In total, 19 lesions (10 lesions were in the right kidney, and 9 lesions were in the left kidney) were ablated using 21 US guided percutaneous MWA sessions (Table 1)

Renal Function
After MWA treatment, no obvious changes of renal function were observed in all patients. Compared with the mean levels prior to the MWA, there were no significant differences in the mean serum Cr and BUN levels 1 day after the MWA procedure (6.48 ± 1.93lmol/L versus 6.17 ± 0.82lmol/L, p=0.683; 107.4 ± 27.90mmol/L versus 124.43 ± 39.51mmol/L, p=0.335) (Figure 3).

Discussion
For the majority of patients with bilateral RCCs, partial or complete nephrectomy has been considered the first choice of treatment [13,14]. However, certain patients are non-surgical candidates or refuse surgery due to comorbidities and cosmetic to assist tumor ablation of liver, kindey, and benign prostatic hyperplasia [15][16][17]. Cheng also reported 24 cases of RCCs adjacent to the intestinal tract using US-guided MWA treatment [7].