Nelson Salas

Initial Experience Using Microwave Ablation Therapy for Renal Tumor Treatment: 18-Month Follow-up

OBJECTIVES To assess efficacy and morbidity of microwave ablation (MWA) for small renal tumors in an initial cohort of patients. MWA is a recently introduced thermal needle ablation treatment modality with theoretical advantages compared with radiofrequency ablation, such as greater intratumoral temperatures, lack of a grounding pad, and superior convection profile. However, experience has been limited in the human kidney. METHODS Ten patients with a single, solid-enhancing renal tumor from June 2008 to November 2008 received laparoscopic or computed tomography-guided percutaneous MWA at a tertiary referral center with ≥14 months of follow-up. MWA was performed using the Valleylab Evident, 915-MHz MWA system at 45 W with intraoperative biopsy before ablation, and peripheral fiberoptic thermometry to determine the treatment endpoints. The patients were followed up with contrast-enhanced computed tomography at 1 month, 6 months to 1 year, and annually to monitor for tumor recurrence. RESULTS The follow-up duration for the 6 male and 4 female patients (mean tumor size 3.65 cm, range 2.0-5.5; mean age 69.8 years) was 17.9 months. The recurrence rate, defined by persistent enhancement, was 38% (3 of 8). The intraoperative and postoperative complication rate was 20% and 40%, respectively. CONCLUSIONS MWA resulted in poor oncologic outcomes with a significant complication rate at an intermediate level of follow-up. However, MWA has promising theoretical advantages and should not be discarded. Additional studies should be considered to better understand the microwave-tissue interaction and treatment endpoints for different size renal masses before widespread use.

Ablative therapies for small renal tumours

Improvements in imaging technology have resulted in an increase in detection of small renal masses (SRMs). Minimally invasive ablation modalities, including cryoablation, radiofrequencey ablation, microwave ablation and irreversible electroporation, are currently being used to treat SRMs in select groups of patients. Cryoablation and radiofrequency ablation have been extensively studied. Presently, cryoablation is gaining popularity because the resulting ice ball can be visualized easily using ultrasonography. Tumour size and location are strong predictors of outcome of radiofrequency ablation. One of the main benefits of microwave ablation is that microwaves can propagate through all types of tissue, including desiccated and charred tissue, as well as water vapour, which might be formed during the ablation. Irreversible electroporation has been shown in animal studies to affect only the cell membrane of undesirable target tissues and to spare adjacent structures; however, clinical studies that depict the efficacy and safety of this treatment modality in humans are still sparse. As more experience is gained in the future, ablation modalities might be utilized in all patients with tumours <4 cm in diameter, rather than just as an alternative treatment for high-risk surgical patients.

Laser interstitial thermotherapy (LITT) monitoring using high-resolution digital mammography: theory and experimental studies.

Laser interstitial thermotherapy (LITT) is a minimally-invasive laser hyperthermia procedure for the treatment of localized tumours. Real-time monitoring of LITT is essential to control the extent of tumour destruction and ensure safe and effective treatments. The feasibility of using high-resolution digital x-ray mammography to monitor LITT of breast cancer was evaluated. Tissue phantoms including polyacrylamide hydrogel and cadaver porcine tissue were heated using a 980 nm diode laser delivered through optical fibres with diffusing tips. Digital images of the tissue phantoms were recorded with a high-resolution digital stereotactic breast biopsy system during heating. The recorded images were processed and analysed to detect heat-induced changes. No changes were detected during heating of the hydrogel. Pixel-by-pixel subtraction of the initial image from images taken during laser heating shows observable thermally-induced changes around the fibre during laser irradiation that correlate with the thermal denaturation zone observed by gross anatomy. These experiments demonstrate that high-resolution digital x-ray mammography can be used to detect heat-induced tissue changes during experimental LITT in fibro-fatty tissue.

Laser Trabeculoplasty Induces Changes in the Trabecular Meshwork Glycoproteome: A pilot study

Laser trabeculoplasty (LT) is a commonly used modality of treatment for glaucoma. The mechanism by which LT lowers the intraocular pressure (IOP) is unknown. With the use of cat eyes, selective laser trabeculoplasty (SLT) with a Q-switched frequency doubled Nd:YAG laser was used to treat the trabecular meshwork (TM). Laser treated TM was then subjected to proteomic analysis for detection of molecular changes and histological analysis for the detection of structural and protein expression patterns. In addition, the protein glycosylation patterns of laser treated and nontreated TM was assessed and differentially glycosylated proteins were proteomically identified. SLT laser treatment to the TM resulted in elevated glycosylation levels compared to nonlasered TM. TM laser treatment also resulted in protein expression levels changes of several proteins. Elevated levels of biglycan, keratocan and prolargin were detected in laser treated TM compared to nonlasered controls. Further investigation is anticipated to provide insight into how glycosylation changes affect TM proteins and TM regulation of aqueous outflow in response to laser trabeculoplasty.

Radiofrequency ablation for treatment of renal tumors: technological principles and outcomes

Radiofrequency ablation (RFA) is a minimally invasive, energy-based, needle-ablative treatment modality that is currently being used to treat small renal masses (SRMs) and offers advantages over extirpative techniques. RFA treats SRM with heat induced by the tissue impedance to radiofrequency current emitted from a needle probe within the SRM. Currently available RFA systems use either an impedance- or temperature-based treatment algorithm to reach treatment end point while minimizing risk of carbonization. Physical limitations, such as electrical property heterogeneity and convective heat loss due to blood flow, and technical considerations should be addressed when performing RFA. Nonetheless, investigations with intermediate follow-up have demonstrated single-treatment radiographic recurrence-free rates of >90%. Future trends include the use of noninvasive imaging thermometry, electromagnetic targeting and adjuvant techniques.

Effects of Microwave Ablation of the Kidney

INTRODUCTION Thermal ablative therapy with cryotherapy and radiofrequency ablation is currently being utilized for treatment of small renal masses. Recently, microwave ablation (MWA) has been investigated for soft tissue destruction, with limited clinical experience for renal masses. This study was designed to evaluate the effectiveness of a new microwave system in the porcine kidney. MATERIALS AND METHODS MWAs were performed in vivo on six pigs using the Evident Microwave Ablation System (Valleylab, Boulder, CO) with a 3.7 cm active tip percutaneous antenna. Ablations were performed in both upper and lower poles at 45 W for 3, 5, and 10 minutes. Three pigs died; three pigs survived for 7 days. After necropsy the kidneys were harvested, ablation zones were measured, and histological analysis was performed. RESULTS The ablated zones at each time interval were inconsistent. The gross appearance of the lesions in both groups was similar. The antenna tract was charred, the collecting system was damaged, and there was asymmetry of the zones of ablation. Histological analysis revealed coagulative necrosis in the area of the ablation with sloughed and denuded urothelium. CONCLUSION MWA of the kidney utilizing this model yields inconsistent geometrical lesions when applied near the renal collecting system. Additionally, microwave energy may be preferentially absorbed by the increased water content in the collecting system resulting in damage to it. Further study is needed to assess the attenuation of the microwave field in the kidney at different locations due to the kidneys heterogeneity.

Laparoendoscopic single site nephrectomy with the SPIDER surgical system: Engineering advancements tested in a porcine model

UNLABELLED Abstract Background and Purpose: The Single Port Instrument Delivery Extended Reach (SPIDER) surgical system was developed for true continuous instrument triangulation during laparoendoscopic single site (LESS) surgery. We present our initial preclinical experience with the SPIDER surgical system during renal surgery. MATERIAL AND METHODS Bilateral laparoscopic nephrectomies were performed in a live adult porcine animal model using the SPIDER device. A standard surgical approach was used via direct video guidance. RESULTS The procedure was successfully performed without surgical error or complication. The SPIDER system proved easy to use with only a minimal learning curve. Intracorporeal surgical knots were tied without difficulty using this single site system. CONCLUSIONS Our initial experience with the SPIDER surgical system during renal surgery is promising. SPIDER allows for true single port instrument triangulation offering a superior operative experience to currently available LESS surgical systems.

Initial experience with laparoendoscopic single-site simple nephrectomy using the TransEnterix SPIDER surgical system: assessing feasibility and safety.

PURPOSE The goal of this report is to describe our initial clinical experience performing a simple nephrectomy with the SPIDER (Single Port Instrument Delivery Extended Reach) laparoendoscopic single-site (LESS) surgical system. PATIENT AND METHODS One patient with a nonfunctioning kidney secondary to a ureteropelvic junction obstruction underwent a simple nephrectomy through a single incision performed using the SPIDER surgical system. We assessed the technical feasibility, efficiency, and perioperative outcomes. RESULTS The SPIDER-LESS nephrectomy was performed successfully without additional skin incisions for laparoscopic ports, instrument clashing, or open conversion. Total operative time was 210 minutes with blood loss of 50  mL. The patient experienced no intraoperative or postoperative complications. Pathologic evaluation confirmed atrophic renal parenchyma. CONCLUSIONS The SPIDER surgical system LESS nephrectomy is feasible and safe. Future refinements of the technology and prospective studies are needed to further optimize its application in urology.

Thermal analysis of laser interstitial thermotherapy in ex vivo fibro-fatty tissue using exponential functions

A therapeutic procedure to treat small, surface breast tumours up to 10 mm in radius plus a 5 mm margin of healthy, surrounding tissue using laser interstitial thermotherapy (LITT) is currently being investigated. The purpose of this study is to analyse and model the thermal and coagulative response of ex vivo fibro-fatty tissue, a model for breast tissue, during experimental laser interstitial thermotherapy at 980 nm. Laser radiation at 980 nm was delivered interstitially through a diffusing tip optical fibre inserted into a fibro-fatty tissue model to produce controlled heating at powers ranging from 3.2 to 8.0 W. Tissue temperature was measured with thermocouples placed at 15 positions around the fibre. The induced coagulation zone was measured on gross anatomical sections. Thermal analysis indicates that a finite sum of exponential functions is an approximate solution to the heat conduction equation that more accurately predicts the time-temperature dependence in tissue prior to carbonization (T < 100 degrees C) during LITT than the traditional model using a single exponential function. Analysis of the ellipsoid coagulation volume induced in tissue indicates that the 980 nm wavelength does not penetrate deep enough in fibro-fatty tissue to produce a desired 30 mm diameter (14.1 x 10(3) mm3) coagulation volume without unwanted tissue liquefaction and carbonization.

Oncologic Outcomes Using Real-Time Peripheral Thermometry-Guided Radiofrequency Ablation of Small Renal Masses

BACKGROUND AND PURPOSE With the increased incidence of low-stage renal cancers, thermal ablation technology has emerged as a viable treatment option for extirpation in selected persons and is supported by the current American Urological Association guidelines. We present a 9-year, single institution experience with radiofrequency ablation (RFA) using real-time peripheral temperature monitoring of small renal masses focusing on oncologic outcomes. PATIENTS AND METHODS We reviewed our prospectively collected database of patients with renal masses who were treated between November 2001 and January 2011 with laparoscopic (LRFA) or CT-guided percutaneous RFA (CTRFA) with simultaneous real-time peripheral fiberoptic thermometry. Patients were followed radiographically at 1 month, 6 months, 1 year, and then annually. Clinicopathologic outcomes were collected and analyzed. RESULTS A total of 274 patients (211 male) aged 18 to 88 years (mean 67 years) with 292 renal tumors underwent LRFA (112) or CTRFA (180). Mean tumor size was 2.5 cm (0.7-5.3 cm). An intraoperative preablation biopsy showed 197 (67.4%) renal-cell carcinomas (RCC), and 77 (26.4%) benign tumors. Mean follow-up was 26 months (1-98 mos). The single ablation treatment radiographic success rate was 96% for all tumors and 94% for RCC. Metastatic RCC developed in one patient, who died. The Kaplan-Meier (KM) 3-year and 5-year cancer-specific survival was 100% and 98.6%, respectively. The KM 3-year and 5-year overall survival was 90.4% and 74.2%, respectively. CONCLUSION RFA is a clinically effective and safe nephron-sparing treatment of patients with small renal masses. Our large cohort and intermediate-term experience adds to the building evidence for the efficacy of RFA for small renal cancers.