Gideon Lorber

Long-term oncologic outcomes following radiofrequency ablation with real-time temperature monitoring for T1a renal cell cancer

OBJECTIVE Few studies report long-term follow-up of renal cancer treated by radiofrequency ablation (RFA), thus limiting the comparison of this modality to well-established long-term follow-up series of surgically resected renal masses. Herein, we report long-term oncologic outcomes of renal cancer treated with RFA in a single institution. METHODS AND MATERIALS We retrospectively reviewed patients treated between November 2001 and October 2012 with laparoscopic-guided or computed tomography-guided RFA. All treatments were performed with real-time thermometry ensuring target ablation temperature (>60°C) was adequately reached. Only patients with biopsy-confirmed T1a-category cancer and a follow-up period>48 months were included in our analysis. Follow-up included office visits, laboratory work, and periodic contrast-enhanced imaging. Survival was calculated using the Kaplan-Meier analysis. Overall complications were reported using the Clavien-Dindo scale. RESULTS Of 434 RFA cases, 53 treatments in 50 patients met the inclusion criteria. Of these, 29 were treated with computed tomography-guided RFA and 24 with laparoscopic-guided RFA. The mean follow-up interval was 65.6 months (48.5-120.2), and the mean renal mass size was 2.3 cm (0.3-4.0). There were 4 (7.5%) local recurrences and 1 case of distant metastases with no local recurrence. The 5-year overall survival was 98%, cancer-specific survival was 100%, and recurrence-free survival was 92.5%. The complication rate was 26.4%, which included 71% of Clavien-Dindo grade I and 29% of grade II. Mean estimated glomerular filtration rate preoperatively and at the most recent follow-up visit was 77 and 66 ml/min, respectively. CONCLUSIONS When performed on selected patients, while monitoring real-time temperatures to ensure adequate treatment end points, RFA offers favorable long-term oncologic outcomes approaching those reported for partial nephrectomy.

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.

Prevention of Initial Biofilm Formation on Ureteral Stents Using a Sustained Releasing Varnish Containing Chlorhexidine: In Vitro Study

BACKGROUND AND PURPOSE Ureteral stents are being used exceedingly in the field of urology, and with advancements in endourology, this trend is increasing. Bacterial colonization and proliferation on the stent surface may result in urinary tract infections (UTIs) necessitating the administration of antibiotics that, in turn, may lead to the development of antibiotic-resistant bacterial strains. Several studies have shown that sustained release varnish (SRV) combined with antibiotics or antiseptics can prevent the proliferation of bacteria on urethral catheters. This is the first study that evaluates this technique implemented on ureteral stents. MATERIALS AND METHODS We evaluated growth inhibition on ureteral stent segments coated with chlorhexidine (CHX) 1% SRV. The tests were conducted using common urinary pathogens: Enterococci, Pseudomonas, and Escherichia coli. Coated stent segments were inserted into bacterial suspensions. Controls included uncoated stent segments and stents coated with placebo SRV (without CHX). RESULTS Bacterial growth measured as turbidity and as colony-forming units showed a significant inhibition effect of initial bacteria adhesion to the CHX-SRV coated stent segments compared with the controls (P<0.001). This inhibitory effect was apparent in each of the bacteria tested and was confirmed by inspection of the stent segments under an electron microscope. In a kinetic experiment using CHX 2% SRV, we were able to prolong the growth inhibition effect from 1 week to nearly 2 weeks. CONCLUSIONS We believe this technique may play a significant role in reducing ureteral stent-associated UTIs. Further studies are needed before this approach can be implemented in clinical practice.

Fever After Shockwave Lithotripsy—Risk Factors and Indications for Prophylactic Antimicrobial Treatment

PURPOSE To identify risk factors for fever after shockwave lithotripsy (SWL) and suggest guidelines for prophylactic antimicrobial treatment. PATIENTS AND METHODS Between 1985 and 2007, a total of 15,324 SWL procedures were performed in our institution using the Dornier HM3 lithotripter. Because stone analyses were not available in the majority of patients, management of stones larger than 2 cm in diameter were excluded from this analysis to minimize the ratio of struvite stones as a possible cause for postprocedural fever. In this analysis, 11,500 SWL treatments were included. Clinical parameters before, during, and after treatments were prospectively registered using a computerized database. Potential risk factors for fever after SWL were evaluated. RESULTS Fever >38.0 degrees C developed in 161 (1.4%) patients. The risk factors for fever after SWL were: A positive urine culture (P < 0.05), an indwelling nephrostomy tube or stent during the procedure (P < 0.001), lithotripsy of kidney or upper ureteral stones (P < 0.05) and preoperative symptomatic urinary tract infection (UTI) (P < 0.05) or sepsis (P < 0.05). Lithotripsy of mid and lower ureteral stones, stone size, and the use of ureteral catheters during the procedures were not associated with increased risk of fever after SWL. CONCLUSIONS Fever (>38.0 degrees C) develops in only 1.4% of the patients undergoing SWL. Therefore, prophylactic antibiotic treatment is not indicated in all patients. Selective prophylactic treatment is recommended in patients who present with UTI, kidney or upper ureteral stones, and those for whom a nephrostomy tube or stent is necessary.

What Happened to Shockwave Lithotripsy During the Past 22 Years? A Single-Center Experience

INTRODUCTION From 1985 to August 2007 we have performed 15,324 shockwave lithotripsy (SWL) treatments using the Dornier HM3 lithotripter. We studied trends in the characteristics of treatments and patients. PATIENTS AND METHODS Patient data were recorded in a computerized database. Changes in characteristics of patients and stones treated during this period were reviewed. RESULTS A total of 15,324 treatments were performed on 10,734 patients. The following trends were observed: (1) Stone size: A significant increase in the proportion of patients treated for stones up to 10 mm in diameter, no change for stone size of 10 to 20 mm, and a decrease in stones larger than 20 mm in diameter. (2) Stone location: A significant increase in the proportion of patients treated for proximal and distal ureteral calculi, whereas a significant decrease in those with renal pelvic and staghorn stones. (3) Auxiliary procedures: A significant increase in the use of perioperative procedures (stents or ureteral catheters) ranging from 20% during the mid-1980s up to 60% in the year 2007. (4) Presenting symptoms: A significant increase in the percentage of patients referred with pain and a significant decrease in the percentage of patients referred with signs of infection. (5) Repeat SWL: A total of 13% of the patients required a second SWL for the same stone within 90 days of the first procedure. (6) Complication rate: This rate was relatively low, ranging from 1% to 6% per year. CONCLUSIONS The evolvement of endourological procedures and techniques resulted in a decreased referral of large kidney stones for SWL. Advanced diagnostic modalities increased the diagnosis of renal colic in patients presenting with pain, and consequently their referral rate and timing for SWL treatment. The use of stents increased because of referral of patients with obstructing stones and infection or for prevention of posttreatment obstruction.

First Place: Sustained-Release Antibacterial Varnish-Coated Biopsy Needle for Reduction of Infection Rates Following Prostate Biopsy—In Vitro Model

BACKGROUND AND PURPOSE During the past decade, the incidence of severe infections after transrectal ultrasonography-guided prostate biopsy has increased. Antibacterial sustained-release varnish has been shown to reduce bacterial infections. This varnish has yet to be tested in the field of urology. We undertook an in vitro study to assess the possibility of reducing infection rates after prostate biopsy by coating the needle with a novel sustained, yet rapid release chlorhexidine varnish (SRV-CHX) specifically modified for prostate biopsy. MATERIALS AND METHODS A model simulating the microbiologic environment of a prostate biopsy was developed. The model consisted of two layers of agar, of which the first represented the rectum and was preinfected with Escherichia coli. The second layer was sterile and represented tissue interposed between the rectum and prostate. SRV-CHX-coated biopsy needles were inserted 12 times through the two layers, into the third agar layer representing the prostate. Infection transmission was determined by assessing bacterial growth at inoculation sites within the agar plate representing the prostate. Bacterial growth inhibition was measured as an inhibition zone on the contaminated agar. RESULTS Testing the antibacterial effect of the SRV-CHX-coated needle, we found a substantial reduction of infection transmission as well as sustained inhibition of bacterial growth compared with control needles. CONCLUSIONS Needles coated with SRV-CHX offer a new strategy in infection control after prostate biopsy. A new strategy of SRV-coated prostate biopsy needles supplemented with various antibacterial agents, combined with prophylactic oral antibiotics should result in decreased infection rates after prostate biopsies. Further in vitro studies are needed to formulate the SRV with an optimal antibacterial agent.

Factors associated with diagnostic accuracy when performing a preablation renal biopsy.

BACKGROUND AND PURPOSE Long-term treatment of patients undergoing definitive management of a small renal mass depends largely on the final pathology determination. Preablation renal biopsy (PABx) is often the only source of determining pathology in patients undergoing thermal ablation of a small renal mass. We sought to evaluate patient and tumor characteristics that may play a role in determining the accuracy of a PABx obtained during radiofrequency ablation (RFA). METHODS This retrospective study included a review of our prospectively collected database of all laparoscopic and CT-guided RFA (LRFA; CTRFA) performed in our center from November 2001 to July 2013. Three 18-gauge core biopsies were obtained per tumor. Pathology samples were stratified into diagnostic (group 1) and nondiagnostic (ND) (group 2). We used univariate and multivariate analysis to identify potential biopsy result-modifying factors including patient characteristics (age, body mass index [BMI]), biopsy approach (CTRFA vs LRFA), tumor size, orientation, depth, and polarity. RESULTS A total of 463 treatments in 411 patients were evaluated. Of these, 66% were CTRFA while 34% were LRFA. Mean patient age was 67.4 years (31-88), mean BMI was 28.3 kg/m(2) (16.6-47.2), and mean tumor size was 2.6 cm (0.3-5.5). There was a total of 73 (15.8%) ND biopsies. On multivariate analysis, CTRFA and medial tumors managed with either CTRFA or LRFA were found to be associated with an increased likelihood of a ND biopsy. CONCLUSION PABx obtained in patients undergoing CTRFA and from medial tumors managed with either CTRFA or LRFA were more likely to be ND. Future RFA patients should be counseled appropriately. Additional biopsy cores may be needed in these subgroups. Further prospective studies are warranted to confirm these findings.

Transected Guidewire Tip Simulating Ureteral Stone

A 62-year-old woman was admitted with a diagnosis of a distal ureteral stone 2 years after antegrade imaging of the kidney. Ureteroscopy revealed a guidewire tip that transected during the antegrade study. The events leading to guidewire transection were reproduced, and a minor modification of current guidewires is suggested to prevent similar incidents.

Mathematical and Ex Vivo Thermal Modeling for Renal Tumor Radiofrequency Ablation with Pyeloperfusion

BACKGROUND AND PURPOSE Radiofrequency ablation (RFA) is an effective technique for the treatment of patients with small renal tumors, although it is often limited to tumors at least 2 cm from the renal pelvis or ureter. Retrograde pyeloperfusion (PPF) of the pelvis with cold saline during RFA may protect the pelvis and ureter. We designed a mathematical and ex vivo model of RFA to investigate the effects of PPF. METHODS Our theoretical model uses heat transfer principles simplifying the RFA probe to a heat-emitting cylinder within a material. In the ex vivo model, an RFA probe was placed 18 mm from the pelvis in porcine kidneys and with temperature probes on either side of the RFA probe. Control trials with no PPF were compared with either cold saline (2°C), warm saline (38°C), or antifreeze (-20°C) pumped into the renal calix at a rate of 60 mL/min. Ablated volumes were measured and confirmed histologically. RESULTS The average steady state temperatures at each probe were highest with no PPF, followed by warm saline, cold saline, then antifreeze. Compared with no PPF, temperatures were significantly (P<0.05) colder with warm saline (-8.4°C), cold saline (-18°C), and significantly colder at the calix (warm -14°C, cold -27°C). While RFA output a constant voltage, significantly lower resistances in warm (171Ω) and cold (124Ω) PPF vs no PPF (363Ω) translated to significantly greater power outputs in warm (40 W) and cold (42 W) vs no PPF (14 W). The ablated volumes were significantly higher in warm saline (2.3 cm(3)) vs cold saline (0.84 cm(3)) and no PPF (1.1 cm(3)). Mathematical modeling produced a predictive temperature curve with R2=0.44. CONCLUSION PPF lowers temperatures throughout the entire kidney during RFA, most notably near the collecting system and is dependent on the temperature of the liquid used. In addition, PPF may cause less charring of the tissue around the probe resulting in lower resistance and higher power outputs.

MP54-06 RADIOFREQUENCY ABLATION OUTCOMES BASED ON RENAL CELL CARCINOMA HISTOLOGIC SUBTYPES

INTRODUCTION AND OBJECTIVES: Radiofrequency ablation (RFA) has been used as a successful modality for treating small renal masses in a minimally invasive, nephron sparing manner. Ablation failures are generally attributed to a vascular heat sink phenomenon. The vascularity, and thereby enhancement pattern, of RCC subtypes varies such that RFA success may be impacted. We sought to determine if outcomes for RFA ablation were significantly different based on RCC subtype. METHODS: All RFAs from two centers with extensive experience in performing RFA were reviewed. Only those with RCC subtype of clear cell or papillary RCC were included in the analysis. Other RCC subtypes (chromophobe n1⁄48, oncocytic neoplasm n1⁄49, mixed n1⁄42) were each small and not included. RFA failure was defined as a >10 HU enhancement on contrast-enhanced CT in a previous zone of ablation. Disease-free survival (DFS) was defined as those patients who had no evidence of disease, either as initial ablation failures or as late recurrences. Groups where compared using the chi-squared or exact T test. The Kaplan-Meir method, using the log-rank test, was used to compare outcomes between RCC histologic subtypes. RESULTS: A total of 229 patients were included in the analysis. The mean age of the cohort was 64.5 +/13.8 years with a median follow-up of 48 (IQR 12-65) months. The mean tumor size of the cohort was 2.5 +/0.8 cm. There was no difference between the papillary and clear cell RCC groups based on age, tumor size or months of follow-up. A total of 181 (75.7%) tumors were clear cell type and 48 (20.1%) papillary type. There were 15 failures in the clear cell subtype and 0 in the papillary subtype, giving an estimated 5-year DFS of 89.7% and 100% for clear cell RCC and papillary RCC respectively (p1⁄40.041). CONCLUSIONS: This is the first report suggesting a significant difference in RFA success based in RCC subtype, with papillary RCC having more favorable outcomes compared to clear cell RCC. Based on this data, further studies looking at how best to follow RFA treated tumors based on subtype is warranted.