Cryoablation of small peripheral renal masses: A retrospective analysis

A Microthermal Sensor for Cryoablation Balloons

Treatment of atrial fibrillation by cryoablation of the pulmonary vein (PV) suffers from an inability to assess probe contact, tissue thickness, and freeze completion through the wall. Unfortunately, clinical imaging cannot be used for this purpose as these techniques have resolutions similar in scale (∼1 to 2 mm) to PV thickness and therefore are unable to resolve changes within the PV during treatment. Here, a microthermal sensor based on the "3ω" technique which has been used for thin biological systems is proposed as a potential solution and tested for a cryoablation scenario. First, the sensor was modified from a linear format to a serpentine format for integration onto a flexible balloon. Next, using numerical analyses, the ability of the modified sensor on a flat substrate was studied to differentiate measurements in limiting cases of ice, water, and fat. These numerical results were then complemented by experimentation by micropatterning the serpentine sensor onto a flat substrate and onto a flexible balloon. In both formats (flat and balloon), the serpentine sensor was experimentally shown to: (1) identify tissue contact versus fluid, (2) distinguish tissue thickness in the 0.5 to 2 mm range, and (3) measure the initiation and completion of freezing as previously reported for a linear sensor. This study demonstrates proof of principle that a serpentine 3ω sensor on a balloon can monitor tissue contact, thickness, and phase change which is relevant to cryo and other focal thermal treatments of PV to treat atrial fibrillation.

Ablation of Small Renal Masses

Renal cell carcinoma is most commonly diagnosed in the sixth or seventh decade of life. Historically, surgical extirpation was the gold standard treatment option for small renal masses. However, given the comorbidities in this elderly population, not all patients are candidates for surgery. The development of minimally invasive ablative therapies has solved the surgical dilemma in this patient population. Furthermore, the 2017 American Urological Association guidelines recommends consideration of percutaneous image guided thermal ablation as a treatment option for masses smaller than 3 cm even in healthy individuals. Percutaneous image guided thermal ablation is an attractive treatment option providing excellent local tumor control, fewer complications, better preservation of the renal functions, faster recovery and shorter hospital stay. Various ablative modalities are available in clinical practice. This includes radiofrequency ablation, cryoablation, microwave ablation, irreversible electroporation, high intensity focused ultrasound, and laser ablation. In this review, we focus on the most commonly used modalities including radiofrequency ablation and cryoablation and to a lesser extent microwave ablation and irreversible electroporation.

The "Lightning bolt" Sign on Computed Tomography during Percutaneous Renal Mass Cryoablation

Ice-ball fracture is a rare and often overlooked entity that may lead to intraprocedural hemorrhage after percutaneous cryoablation of renal masses. There is scant literature on ice-ball fractures associated with percutaneous renal cryoablation. Immediate recognition of the lightning bolt sign during intraprocedural computed tomography can help identify patients who may have developed this complication.

Focal ablation therapy for renal cancer in the era of active surveillance and minimally invasive partial nephrectomy

Partial nephrectomy is the optimal surgical approach in the management of small renal masses (SRMs). Focal ablation therapy has an established role in the modern management of SRMs, especially in elderly patients and those with comorbidities. Percutaneous ablation avoids general anaesthesia and laparoscopic ablation can avoid excessive dissection; hence, these techniques can be suitable for patients who are not ideal surgical candidates. Several ablation modalities exist, of which radiofrequency ablation and cryoablation are most widely applied and for which safety and oncological efficacy approach equivalency to partial nephrectomy. Data supporting efficacy and safety of ablation techniques continue to mature, but they originate in institutional case series that are confounded by cohort heterogeneity, selection bias, and lack of long-term follow-up periods. Image guidance and surveillance protocols after ablation vary and no consensus has been established. The importance of SRM biopsy, its optimal timing, the type of biopsy used, and its role in treatment selection continue to be debated. As safety data for active surveillance and experience with minimally invasive partial nephrectomy are expanding, the role of focal ablation therapy in the treatment of patients with SRMs requires continued evaluation.

The management of small renal masses: what is likely to change?

The diffusion of imaging has determined an increased discovery of small renal masses (SRMs). Recent publications have been reviewed to present the state of the art in the management of SRMs and to try to foresee the next steps in this challenging condition. The role of percutaneous biopsies is expanding, since management algorithms include also active surveillance and ablative therapies. However up to 30% of biopsies fail to provide histological diagnosis and there is the risk of under-evaluating high-grade tumors. Active surveillance has been proposed in patients with reduced life expectancy and numerous comorbidities. The average growth of SRMs is slow, and metastatic progression has been observed in about 1%. Ablative therapies (cryotherapy and radiofrequency ablation) are used in patients with relevant comorbidities or advanced age and unfit for surgery, but who desire active treatment. Compared to conservative surgical treatment both techniques have increased local progression rates, while metastatic progression is relatively low.Partial nephrectomy (PN) is the recommended curative treatment for SRMs and can be performed open, laparoscopically or robotically. Open PN represents the benchmark, with similar cancer specific survival and better preservation of renal function compared to nephrectomy. Laparoscopy is comparable to open surgery in terms of oncologic results, but a long learning curve is necessary. Perioperative outcomes of robot-assisted PN appear superior to laparoscopy and the learning curve is shorter, but data for oncological results are still immature. With the increasing diffusion of robotic technology it is likely more SRMs will be managed with this approach.

Results of a prospective study comparing the clinical efficacy of cryoablation of renal cell cancer followed by immediate partial nephrectomy

PURPOSE

Evaluation if cryoablation of small renal tumours (RT) would facilitate the technique of laparoscopic partial nephrectomy (LPN) in a prospective study.

PATIENTS AND METHODS

In a prospective non-randomised study between April 2007 and October 2009, 16 patients with a mean age of 68 years (48-80 years) and a peripherally located RT were candidates for nephron-sparing surgery (5 open partial nephrectomy (OPN), 11 LPN). Cryoablation of RT was followed in the same session by open (K-OPN) and laparoscopic (K-LPN) partial nephrectomy. Perioperative and follow-up parameters were estimated. A matched-pair cohort of 41 patients (20 OPN, 21 LPN) who underwent standard operations due to the same indication has been selected for retrospective comparison (controls).

RESULTS

Mean age for K-OPN was 74 years (69-83) with mean blood loss 140 ml (50-200); for K-LPN: 66.6 years (48-80) with 100 ml (50-700). All procedures were completed successfully without conversions (K-LPN), transfusions or intra-operative complications. Compared to OPN/LPN, K-OPN and K-LPN were associated with a longer operative time (P < 0.05) and a comparable postoperative hospital stay. There were no early postoperative complications. Cryoablation has not affected the histopathological evaluation of tumours or resection margins. Histopathology showed cytologic changes suggesting fresh coagulative necrosis, glomerular vascular congestion and interstitial haemorrhages following cryotherapy. One patient (K-LPN) developed a pararenal abscess necessitating puncture after 7 weeks. The follow-up (9-42 months) was uneventful.

CONCLUSIONS

The current study shows that K-LPN is feasible without increasing procedure morbidity or compromising surgical and oncological outcomes. It adds no advantage to tumour excision. Pathological findings document early cryoablation effects but viable tissue.

Review of the efficacy and safety of cryoablation for the treatment of small renal masses

PURPOSE

Small renal masses are increasingly being discovered incidentally on imaging for another reason. The standard of care of these masses involves excision by open or laparoscopic techniques. Recently, ablative techniques, such as radiofrequency ablation (RFA) and cryoablation, have taken a more prominent role in the treatment algorithm of these masses. We evaluate the effectiveness and safety of cryoablation to treat renal tumours.

METHODS

A review of the literature was conducted. There was no language restriction. Studies were obtained from the following sources: the Cochrane Library, PUBMED, EMBASE and LILACS.

RESULTS

There was no clinical trial identified in the literature. Thus, we described the results from 23 case series and retrospective studies with a reasonable sample size (number of reported patients in each study ≥30), with a total of 2104 analyzed tumours from 2038 patients. There was wide variability in the outcomes reported, but success rates were generally good. Follow-up was generally short, but some series reported outcomes at 5 years. The most common complications reported were hemorrhage (some of the patients requiring transfusion), perinephric hematoma and urine leaks.

CONCLUSION

Cryoablation presents a feasible treatment for patients with small renal masses. Only short-term data are available and, as such, meaningful conclusions regarding long-term cancer control cannot be made. More rigorous studies are needed.

Cryotherapy and its applications in the management of urologic malignancies: a review of its use in prostate and renal cancers

Cryotherapy has been established as an ablative modality for the treatment of a wide range of malignancies. Being minimally invasive, it is associated with less morbidity than conventional extirpative surgical procedures. In recent years, it has been used with success for treating two of the common urologic malignancies, that is, prostate and renal cancer. In this review, we highlight the role of cryotherapy as a treatment modality, the proposed destructive mechanisms of action and the risks of its use in the management of prostate and renal malignancy.

Thermoablation of Renal Masses: The Urologist's Perspective

Thermoablation (TA) has become an increasingly popular treatment for small renal masses (SRMs). Although long-term outcomes are not currently reported, TA may have a role in being an alternative to radical or partial nephrectomy. This review gives a broad overview of TA and discusses current controversies in the field.

Ex vivo model for renal fracture in cryoablation

OBJECTIVE

To demonstrate the formation of fractures due to cryoablative therapy in a controlled model and validate the new model for the study of the complication of fractures during renal cryoablation.

METHODS

Endocare PERC-17 (1.7 mm) and Galil 17 ga IceRod (1.47 mm) probes were selected because of similar diameter and reported ice-ball size. The ex vivo model used here was a porcine kidney obtained at the supermarket. The kidneys were subsequently bivalved. The cryoprobes were inserted running just underneath the cut surface, entering the lateral surface of the kidney, and directed toward the medial surface of either the upper or lower pole. In this manner, we avoided the major calyces and involved the most parenchyma. Freeze-thaw-freeze cycles of various durations were performed. The probes were frozen parallel to each other at a distance of 20 mm apart.

RESULTS

Evidence of cryoablation-induced fracture included popping sounds noted during thaw and cracks that became visible during the phase of second freeze. Cracks were noted to extend from the probe through the parenchyma. In multiple probe freezes, the intervening zone between the 2 ice-balls had smoother ice and the fractures that appeared there originated at either probe. Fracture formation was only observed with the Endocare probes, with single or parallel freezes. No fractures were noted in the IceRod freezes.

CONCLUSION

The bivalved ex vivo kidney is an inexpensive, representative, and demonstrative model for study of fracture during cryoablation.

Expression of S100A4 in renal epithelial neoplasms

Expression of S100A4 has been associated with progression and poor clinical outcome in a variety of malignancies including those of the breast, pancreas, bladder, and thyroid. To date, the expression of S100A4 protein in renal epithelial neoplasms is poorly understood. In this study, we evaluated the expression of S100A4 protein and mRNA in the nontumoral kidney and renal epithelial neoplasms of different types and correlated its expression with patient outcome. The study population included 155 clear cell renal cell carcinomas (cRCC), 22 papillary renal cell carcinomas (pRCC), 13 chromophobe renal cell carcinomas and 13 oncocytomas. In nontumoral kidney, nuclear and cytoplasmic S100A4 staining was detected in the glomerular epithelium and endothelium, distal tubules and collecting ducts, and loops of Henle. A different expression pattern was noted in the various neoplasms. S100A4 expression was significantly increased in the stromal cells in cRCC (83%) and pRCC (73%) compared with paired nontumoral kidney tissue (P<0.001). There was no increased stromal cell expression of S100A4 in oncocytomas and chromophobe carcinomas. Positive epithelial staining was more common in pRCC (58%) than cRCC (11%) (P=0.01). The level of mRNA detected by reverse transcription-polymerase chain reaction was significantly higher in the tumor as opposed to normal tissue in cRCC but not in the other neoplasms (P=0.03). Multivariate analysis revealed that epithelial S100A4 protein expression is an independent poor prognostic factor along with grade and stage only in cRCC (P<0.01). Although S100A4 protein was expressed in a minority of cRCC, its expression was associated with shorter overall patient survival.

The role of pathology in small renal mass laparoscopic cryoablation

Objective. We evaluated histological outcome of intraoperative biopsies at laparoscopic renal mass cryoablation (LCA), prevalence of peritumoral fat tissue invasion, and risk of tract seeding. Methods. Patients were biopsied 3–5 times (16-gauge). Histology was analyzed by general pathologists and reviewed. Peritumoral fat was histologically examined. The trocar used for biopsy-guidance was examined by cytology. Records were studied for reporting tract metastasis. Results. 77 biopsied renal masses with mean ± SD diameter 30 ± 7.4 mm were histologically classified by primary and review pathology revealing 64 and 62 malignancies, 13 and 15 benign lesions, respectively. In 30/34, the fat covered a carcinoma but revealed no malignancy. Cytology showed no malignant cells but was inconclusive in 1 case. No tract metastasis occurred. Conclusions. The use of an intraoperative biopsy protocol provides histological diagnosis of all renal masses. No existence of peritumoral fat tissue invasion or tract seeding was found.

Ablative therapies for renal tumors

Owing to an increased use of diagnostic imaging for evaluating patients with other abdominal conditions, incidentally discovered kidney masses now account for a majority of renal tumors. Renal ablative therapy is assuming a more important role in patients with borderline renal impairment. Renal ablation uses heat or cold to bring about cell death. Radiofrequency ablation and cryoablation are two such procedures, and 5-year results are now emerging from both modalities. Renal biopsy at the time of ablation is extremely important in order to establish tissue diagnosis. Real-time temperature monitoring at the time of radiofrequency ablation is very useful to ensure adequacy of ablation.

Current status of ablative therapies for renal tumors

The increase in detection of small (≤ 4 cm) renal cortical neoplasms has made nephron-sparing surgery the new standard of care for T1a renal lesions. Advances in minimally invasive surgery have improved the surgical approach to these lesions to include laparoscopic partial nephrectomy and renal ablative therapies. In this review, we discuss the indications, outcomes, and potential complications of the commonly used ablative modalities in urologic practice. We will expand on renal cryoablation and review the mechanism of action, surgical approaches, and evidence based medicine using this modality.

Laparoscopic renal cryoablation using ultrathin 17-gauge cryoprobes: mid-term oncological and functional results

Study Type - Therapy (case series).

LEVEL OF EVIDENCE

4. What's known on the subject? and What does the study add? Laparoscopic Cryoablation of renal masses has a low persistence and recurrence rates at short term follow-up albeit higher than Partial Nephrectomy. Long term results are scarcely reported. It is however a NSS technique suitable for high-risk that preserves renal function. The study provides (1) mid-term oncological outcomes of laparoscopic cryoablation of renal masses stratified by primary pathology (RCC, benign mass or undetermined biopsy) and (2) data on renal function evolution up to one year of follow-up supporting the fact that the only predictor of (moderate)renal insufficiency development after Laparoscopic cryoablation is the eGFR at baseline.

OBJECTIVE

To present the functional and oncological mid-term results of laparoscopic cryoablation of renal masses using third generation ultrathin (17-gauge[G]) cryoprobes.

PATIENTS AND METHODS

• Consecutive patients with small renal masses treated by cryoablation from September 2003 to September 2008 were prospectively evaluated. The cryoablation was performed using multiple third generation 17-G cryoprobes after intraoperative mass biopsy. • Data on serum creatinine measurements and cross sectional imaging (computed tomography/magnetic resonance imaging) were regularly collected according to a previously determined protocol. Follow-up was censored in October 2009. • Renal function analysis was based on estimated glomerular filtration rate (eGFR) at 1 year compared with baseline. Residual (or persistent tumour) and recurrence were defined as the presence of residual enhancement at first follow-up and 'de novo' enhancement of a non-enhancing cryolesion at any time during follow-up. • Survival data were analysed using the Kaplan-Meier method. Best estimates for the overall survival (OS), recurrence-free survival (RFS), cancer-specific survival (CSS) and metastatic-free survival (MFS) were made for patients with renal cell carcinoma (RCC) and for patients with RCC or non-diagnostic biopsy.

RESULTS

• A total of 92 patients (100 tumours; mean size 2.5 ± 0.8 cm) were treated in 95 sessions. The mean follow-up was 30.2 ± 16.6 months (Mean values are ±SD). • Intraoperative biopsy showed RCC in 51 patients (53.7%), benign lesion in 23 patients (24.2%) and was non-diagnostic in 21 patients (22.1%). Three tumour persistences and four radiological recurrences were detected. • The estimated mean RFS time and 3-year OS and RFS in patients with RCC exclusively were 47.8 (95% confidence interval [CI]: 44.1-51.1) months, 86.1% (95% CI: 71.2-93.6) and 91.8% (95% CI: 76.3-97.3), respectively. The figures were slightly higher in the group of patients with RCC or unknown pathology. The actual CSS and MFS rates were 100%. • Renal function was preserved in 84.5% of patients with normal preoperative eGFR. • Baseline eGFR was the only predictor of renal insufficiency development at 1-year follow-up.

CONCLUSION

Laparoscopic cryoablation with multiple ultrathin cryoprobes is oncologically and functionally effective at mid-term follow-up.

The importance of nephron-sparing focal therapy: renal function preservation

Historically, renal cancer has been treated with radical nephrectomy. Consequently, many patients developed renal insufficiency and the health problems associated with this. With the increasing diagnosis of small renal masses, nephron-sparing treatments have been developed to treat these masses adequately, while maximizing renal function. Focal ablative therapy is a means to treat small renal masses in a minimally invasive manner. Yet, there are few studies that have focused on their ability to preserve renal function. In this article, we review the existing literature on the renal function outcomes of patients treated with either radio frequency ablation or cryoablation.

Cell death along single microfluidic channel after freeze-thaw treatments

Cryotherapy is a prospective green method for malignant tumor treatment. At low temperature, the cell viability relates with the cooling rate, temperature threshold, freezing interface, as well as ice formation. In clinical applications, the growth of ice ball must reach a suitable size as cells could not be all killed at the ice periphery. The cell death ratio at the ice periphery is important for the control of the freezing destruction. The mechanisms of cryoinjury around the ice periphery need thorough understanding. In this paper, a primary freeze-thaw control was carried out in a cell culture microchip. A series of directional freezing processes and cell responses was tested and discussed. The temperature in the microchip was manipulated by a thermoelectric cooler. The necrotic and apoptotic cells under different cryotreatment (duration of the freezing process, freeze-thaw cycle, postculture, etc.) were stained and distinguished by propidium iodide and fluorescein isothiocyanate (FITC)-Annexin V. The location of the ice front was recorded and a cell death boundary which was different from the ice front was observed. By controlling the cooling process in a microfluidic channel, it is possible to recreate a sketch of biological effect during the process of simulated cryosurgery.

The impact of renal tumor size on the efficacy of laparoscopic renal cryoablation

PURPOSE

We evaluated the impact of renal tumor size on the oncologic and surgical efficacy of laparoscopic renal cryosurgery (LRC) according to our intermediate-term experience in Korea.

MATERIALS AND METHODS

From June 2005 to October 2008, we enrolled 37 patients who underwent LRC for 40 renal tumors. Patients were stratified into four groups according to renal tumor size. Patients who presented with a maximum tumor diameter (MTD) of at least 1 cm but less than 2 cm were assigned to Group 1, those with an MTD equal to or greater than 2 but less than 3 cm were assigned to Group 2, those with an MTD equal to or greater than 3 but less than 4 cm were assigned to Group 3, and those with an MTD equal to or greater than 4 cm were assigned to Group 4. Oncologic and clinical outcomes in each group were compared.

RESULTS

The four groups showed no statistically significant differences in preoperative variables, including age, sex, body mass index, American Society of Anesthesiologists scores, baseline renal function and hemoglobin, and length of hospital stay. Regarding surgical aspects, however, operation time, estimated blood loss, and postoperative complications were significantly increased in patients with larger tumors. Three patients in Group 3 required postoperative transfusions, and 1 patient in Group 4 required conversion to open renal cryosurgery. During the mean follow-up period of 31.6 months, radiologic evidence of tumor recurrence was found in only 2 patients in Group 4.

CONCLUSIONS

In this series, LRC for renal tumors smaller than 3 cm was conducted safely without radiologic evidence of tumor recurrence during intermediate-term follow-up. For tumors larger than 3 cm, however, the transfusion rate increased, and for renal tumors larger than 4 cm, the tumor recurrence rate increased significantly.

A critical analysis of the actual role of minimally invasive surgery and active surveillance for kidney cancer

CONTEXT

The incidence of renal cell carcinomas (RCCs) has increased steadily-most rapidly for small renal masses (SRMs). Paralleling the changing face of RCC in the past 2 decades, new, less invasive surgical options have been developed. Laparoscopic radical nephrectomy (LRN) is an established procedure for the treatment of RCC. Treatment of SRMs includes open partial nephrectomy (OPN), laparoscopic partial nephrectomy (LPN), thermal ablation, and active surveillance.

OBJECTIVE

To present an overview of minimally invasive treatment options and data on surveillance for kidney cancer.

EVIDENCE ACQUISITION

Literature and meeting abstracts were searched using the terms renal cell carcinoma, minimally invasive surgery, laparoscopic surgery, thermal ablation, surveillance, and robotic surgery. The articles with the highest level of evidence were identified with the consensus of all the collaborative authors and reviewed.

EVIDENCE SYNTHESIS

Renal insufficiency, as measured by the glomerular filtration rate, occurs more often after radical nephrectomy than partial nephrectomy (PN). OPN and LPN show comparable results in long-term oncologic outcomes. The treatment modality for SRMs should therefore be nephron-sparing surgery (NSS). In select patients, thermal ablation or active surveillance of SRMs is an alternative.

CONCLUSIONS

LRN has become the standard of care for most organ-confined tumours not amenable to NSS. Amongst NSS options, PN is the treatment of choice, yet remains underutilised in the community. Initial data during its learning curve revealed that LPN had higher urologic morbidity. However, current emerging data indicate that in experienced hands, LPN has shorter ischaemia times, a lower complication rate, and equivalent long-term oncologic and renal functional outcomes, yet with decreased patient morbidity compared to OPN. Robotic partial nephrectomy is being explored at select centres, and cryotherapy and radiofrequency ablation are options for carefully selected tumours. Active surveillance is an option for selected high-risk patients. Percutaneous needle biopsy is likely to gain increasing relevance in the management of small renal tumours.

Surveillance as an option for the treatment of small renal masses

OBJECTIVES. To review the natural history and biological potential of small renal masses in order to evaluate surveillance as a treatment option. METHODS. Literature search of Medline and additional references from non-Medline-indexed publications concerning surveillance of small renal masses. RESULTS. The natural history and biological potential of small renal masses can still not be unambiguously predicted at present. There seems to be no clear correlation between tumour size and presence of benign histology. The majority of small renal masses grow and the majority are cancer, but one cannot safely assume that a lack of growth on serial CT scans is the confirmation of absence of malignancy. Needle core biopsies could be used to help in decision making. They show a high accuracy for histopathological tumour type but are less accurate in evaluating Fuhrman grade. CONCLUSIONS. At present, surveillance of small renal masses should only be considered in elderly and/or infirm patients with competing health risks, in those with a limited life expectancy, and in those for whom minimal invasive treatment or surgery is not an option. In all other patients, active surveillance should only be considered in the context of a study protocol. Long-term, prospective studies are needed to provide a more accurate assessment of the natural history and metastastic potential of small renal masses.

Laparoscopic renal tumor cryoablation: appropriate application of real-time ultrasonographic monitoring

BACKGROUND AND PURPOSE

Many authors who report outcomes of laparoscopic cryoablation for renal tumors comment that real-time intracorporeal ultrasonographic monitoring of the ice-ball formation is imperative. In our experience, ultrasonographic monitoring of the ice-ball formation necessitates significantly more mobilization of the kidney, and the images are difficult to interpret because of artifact and the cryoablation effect on the tissue. We report our intermediate outcomes for laparoscopic cryoablation without real-time ultrasonographic monitoring of the ice ball.

PATIENTS AND METHODS

Between December 2002 and May 2007, 27 patients underwent laparoscopic renal cryoablation. The cryoablation approach was based on tumor location and surgeon preference. Lesions were identified and overlying fat was excised, without further mobilization. Real-time ultrasonographic measurement and mapping of the renal lesion were performed. All lesions were biopsied before cryoablation. A double 10-minute freeze-thaw cycle was performed. Postoperative follow-up comprised serial imaging at months 1, 3, 6, and 12 and yearly thereafter.

RESULTS

Mean patient age was 70.1 years with a mean renal tumor size of 2.2 cm. Sixteen (59.3%) patients had more than three comorbidities and six (22.2%) patients had two comorbidities with at least 1 previous intra-abdominal surgery. An average of four cryoablation probes were used per lesion. The serum creatinine level was 1.3 mg preoperatively and 1.4 mg at last follow-up. At follow-up of 22 months, there were no local recurrences and 1 (3%) metastatic lesion.

CONCLUSION

Laparoscopic cryoablation of small renal masses continues to be a safe and effective technique, even without the use of real-time ultrasonographic monitoring of the ice ball.

Decision tree for laparoscopic partial nephrectomy versus laparoscopic renal cryoablation for small renal masses

PURPOSE

We propose an algorithm to help guide surgeons' decisions between laparoscopic partial nephrectomy (LPN) and renal laparoscopic cryoablation (LCA) based on preoperative parameters and outcomes defined in the literature.

PATIENTS AND METHODS

From July 2004 to December of 2007, we performed 51 LPNs and 22 LCAs. We formulated an algorithm between LPN and LCA based on outcomes from published series. Candidates for LPN are younger than 70 years; have few comorbidities; masses < or = 7 cm; and solitary, solid, and or cystic masses with an exophytic or mesophytic location. Candidates for LCA are 70 years old or older, with multiple comorbidities, masses < or = 3.5 cm, multiple masses, solid masses only, and include endophytic or hilar tumors. We then applied this decision tree to our series.

RESULTS

Our results for LPN are statistically similar to the published series except there was a higher positive margin rate in our series (11.8 v 3.5%). Our LCA series had older patients (71 v 65 y), larger masses (3.2 v 2.5 cm), and a higher rate of bleeding necessitating transfusion (18%). We applied the algorithm to all 73 patients in our series. It estimated that 45 patients should undergo LPN and 28 should undergo LCA. A correlation between the predicted surgery and the surgery performed was seen, but approximately one in five patients would have a change in the surgery performed.

CONCLUSIONS

This algorithm validates decisions surgeons are already making between LPN and LCA. While not a perfect model, it can be used to help simplify decisions between these two minimally invasive procedures to achieve optimal outcomes.

Increasing the number of biopsy cores before renal cryoablation increases the diagnostic yield

BACKGROUND AND PURPOSE

Renal cryoablation has been established as a primary management option for many small renal masses. Biopsy is performed intraoperatively and typically consists of one core being taken. This method was used to reduce the potential for seeding tumor and to minimize bleeding, although there have been no reports of tumor formation caused by biopsy seeding and blood loss is minimal. It is also associated with a relatively high yield of nondiagnostic cores. As such, in March 2005, we began taking three biopsy cores rather than one in an attempt to decrease our nondiagnostic rate.

MATERIALS AND METHODS

Biopsy results were retrospectively reviewed for patients who underwent renal cryoablation by two surgeons between February 2001 and July 2007. Findings were stratified according to the number of cores taken, which was either one or three. Tests for significance were performed using the chi-square test to determine if there was a difference in the nondiagnostic rates and the cancer yield rates.

RESULTS

Results of 119 biopsies were reviewed. Of those, a single core was taken from 81 (68%) lesions. Of these, 49 (60%) were malignant and 14 (17%) were nondiagnostic. The remaining 38 (32%) had three cores taken. Twenty-seven (71%) of these were malignant and two (5%) was nondiagnostic. The P values for cancer yield rates and nondiagnostic rates were 0.248 and 0.030, respectively.

CONCLUSIONS

Using a three-core biopsy strategy resulted in an 11% increase in cancer yield and a 12% reduction in nondiagnostic rate. Decreasing the nondiagnostic rate may help in counseling patients at follow-up. Continued investigation is warranted and under way.

Thermal ablation: update and technique at a high-volume institution

In the era of nephron-sparing surgery for small renal tumors, thermal ablation is gaining popularity. Both cryoablation and radiofrequency ablation have well-demonstrated short-term oncologic efficacy and safety. This article shares the current literature and the radiofrequency ablation technique at a high-volume institution. Cases are presented that illustrate solutions to obstacles frequently encountered during percutaneous ablation of renal masses.

Minimally invasive surgery using ablative modalities for the localized renal mass

Due to a number of evolving devices and modalities to treat the small, localized renal mass, the physician and patient have the opportunity to choose an appropriate therapy from several treatment options. Minimally invasive surgery to ablate a localized renal tumor is an alternative strategy to nephron-sparing surgery for the small renal mass. Even though partial nephrectomy has been established as an optimal technique for nephron-sparing surgery, patients who have comorbidities and renal insufficiency would potentially benefit from less invasive treatment. With respect to those concerns, several articles are discussed here regarding thermal ablative therapy for the small renal mass along with oncological outcomes and complications among these modalities compared to conventional procedures. In this review, a comprehensive PubMed search was conducted. For the purposes of reviewing the current status of thermal ablative modalities for the small renal mass, only articles written in English published from 1992 to 2009 were considered. Cryoablation and radiofrequency ablation are the most utilized and potentially promising therapies that are evolving as nephron-sparing minimally invasive surgery for patients with a localized renal tumor. High-intensity focused ultrasound, a relatively new modality to treat the renal mass, needs further study. All modalities require long-term follow up with unified reporting methods in terms of patient selection, pre- and post-treatment evaluation, treatment description, and analysis of outcome.

Cryoablation or radiofrequency ablation of the small renal mass : a meta-analysis

BACKGROUND

The incidence of renal cell carcinoma is rising because of incidental detection of small renal masses (SRMs). Although surgical resection remains the standard of care, cryoablation and radiofrequency ablation (RFA) have emerged as minimally invasive treatment alternatives. The authors of this report performed a comparative meta-analysis evaluating cryoablation and RFA as primary treatment for SRMs.

METHODS

A search of the MEDLINE database was performed reviewing the world literature for clinically localized renal masses treated by cryoablation or RFA.

RESULTS

Forty-seven studies representing 1375 kidney lesions treated by cryoablation or RFA were analyzed. No differences were detected between ablation modalities with regard to mean patient age (P = .17), tumor size (P = .12), or duration of follow-up (P = .53). Pretreatment biopsy was performed more often for cryoablated lesions (82.3%) than for RFA (62.2%; P < .0001). Unknown pathology occurred at a significantly higher rate for SRMs that underwent RFA (40.4%) versus cryoablation (24.5%; P < .0001). Repeat ablation was performed more often after RFA (8.5% vs 1.3%; P < .0001), and the rates of local tumor progression were significantly higher for RFA (12.9% vs 5.2%; P < .0001) compared with cryoablation. The higher incidence of local tumor progression was found to be correlated significantly with treatment by RFA on univariate analysis (P = .001) and on multivariate regression analysis (P = .003). Metastasis was reported less frequently for cryoablation (1.0%) versus RFA (2.5%; P = .06). Cryoablation usually was performed laparoscopically (65%), whereas 94% of lesions that were treated with RFA were approached percutaneously.

CONCLUSIONS

Ablation of SRMs is a viable strategy based on short-term oncologic outcomes. Although extended oncologic efficacy remains to be established for ablation modalities, the current data suggest that cryoablation results in fewer retreatments and improved local tumor control, and it may be associated with a lower risk of metastatic progression compared with RFA.

Renal thermal ablative therapy

Energy targeting is greatly enhanced through imaging modalities, which greatly assist needle placement or energy delivery to the optimal location for maximal effectiveness. When vital structures obscure access to the renal lesion, laparoscopic mobilization of these structures with direct visualization of the tumor can increase the likelihood of ablation success and minimize complication risk. Ablative therapies are attractive because of their minimal impact on patient quality of life in addition to their morbidity and cost. Although they show promise of efficacy, they must be evaluated with long-term follow-up before they are considered the standard of oncologic care. Renal masses can be treated with a laparoscopic or percutaneous approach depending on tumor location, size, and the available technology and experience of the center.

Cryoablation for small renal masses

Advances in imaging techniques (CT and MRI) and widespread use of imaging especially ultrasound scanning have resulted in a dramatic increase in the detection of small renal masses. While open partial nephrectomy is still the reference standard for the management of these small renal masses, its associated morbidity has encouraged clinicians to exploit the advancements in minimally invasive ablative techniques. The last decade has seen the rapid development of laparoscopic partial nephrectomy and novel ablative techniques such as, radiofrequency ablation (RFA), high-intensity focused ultrasound (HIFU), and cryoablation (CA). In particular, CA for small renal masses has gained popularity as it combines nephron-sparing surgery with a minimally invasive approach. Studies with up to 5-year followup have shown an overall and cancer-specific 5-year survival of 82% and 100%, respectively. This manuscript will focus on the principles and clinical applications of cryoablation of small renal masses, with detailed review of relevant literature.