Review of minimally invasive renal therapies: Needle-based and extracorporeal

Cryosurgical Ablation of Renal Cell Carcinoma

BACKGROUND

Small renal masses are being commonly diagnosed incidentally in older patients. A partial nephrectomy is the first-line nephron sparing treatment option for these lesions. However, probe ablative therapy such as cryoablation is emerging as an alternative option for select patients requiring nephron sparing surgery.

METHODS

The current literature regarding the management of small renal lesions with cryoablation was retrospectively reviewed. We selected six of the largest published series of renal cryoablation with a total of 320 patients. The diagnosis, staging, treatment options, mechanism, efficacy and morbidity associated with renal cryoablation were evaluated.

RESULTS

Renal cryoablation for localized small renal masses is well tolerated and associated with a low complication rate. The range of mean tumor size in our literature review series (320 patients) was 2.3 to 2.6 cm. After a range of mean follow-up of 5.9 to 72 months, including a series with a minimum of 5 years of follow-up, the cancer specific survival was 97% to 100% and overall patient survival was 82% to 90.2%.

CONCLUSIONS

Renal cryoablation, based on available clinical reports, appears to be a curative option for patients with small localized renal cell carcinomas (RCCs) who are unwilling or unable to undergo a partial nephrectomy. With encouraging intermediate oncological follow-up available, longer-term follow-up is needed to validate the use of cryoablation as a primary treatment option.

Thermal ablative therapies for treatment of localised renal cell carcinoma: a systematic review of the literature

BACKGROUND AND AIMS

Small renal masses are commonly diagnosed incidentally. The majority are malignant and require intervention. The gold standard treatment is partial nephrectomy unless the patient has significant co-morbidities when surveillance or ablative therapies are utilised. The latter are relatively novel and their long-term efficacy and safety remain generally poorly understood. We performed a literature review to establish the current evidence on the oncological outcome of thermal ablative techniques in small renal masses treatment.

METHODS AND RESULTS

A systematic literature search was performed using PubMed, supplemented with additional references. Articles were reviewed for data on indications, tumour characteristics, ablative techniques, oncological outcome, impact on renal function and complications. The vast majority of articles identified were observational studies. There has not been any direct comparison against partial nephrectomy. Radiofrequency ablation and cryoablation are the techniques that are more commonly used. They have favourable oncological results on intermediate follow-up and indications that successful outcome is sustained long term. The morbidity and impact on renal function appear to be minimal.

CONCLUSION

Thermal ablative therapies are valid alternatives to partial nephrectomy for the treatment of small renal masses in patients unfit for surgery. Prospective long-term data will be needed before the indications for their use expand further.

State-of-the-art surgical management of renal cell carcinoma

There is a recognizable increase in the incidence of renal cell carcinoma and a parallel rise in the surgical management of renal cell carcinoma has occurred. However, recent literature shows that not all small, suspected renal cell carcinoma needs to be treated surgically, especially in elderly patients or those with multiple medical comorbidities. The surgical options for renal cell carcinoma have expanded from traditional open nephrectomy to partial nephrectomy and, at present, more recent outcomes data are available for the laparoscopic versions of these surgeries. Short-term results of thermal ablative technology (radiofrequency and cryoablation) show real promise as minimally invasive therapies. This review examines the most up-to-date outcomes and future directions of the surgical management of renal cell carcinoma.

Laparoscopic radiofrequency ablation of renal tumors: 32-month mean follow-up results of 106 patients

OBJECTIVE

To report our experience of laparoscopic radiofrequency ablation (RFA) on patients with renal tumors. RFA has been increasingly applied in the management of small renal tumors. However, it was performed mostly via percutaneous approach, with limited cases and a short follow-up period.

METHODS

From February 2006 to March 2008, laparoscopic RFA was performed on 106 renal tumors (size range: 0.9-5.5 cm) in 106 selected patients (74 men and 32 women, age range: 25-81 years). Initial contrast-enhanced computed tomography (CT) examination was performed seven days after the procedure, with subsequent CT assessment at three months, six months, and every six months thereafter. Serum creatinine measurement was conducted along with each time CT examination.

RESULTS

The mean follow-up period was 32 months (range: 12-48). All 106 tumors were biopsied before RFA, of which 90 were diagnosed as renal cell carcinoma (RCC) (84.90%). There was one incomplete ablation. One case with radiographic local recurrence was then proved by pathologic analysis of the nephrectomy specimen to have no cancer cells. The local tumor control rate was 98.1% (104/106). Of the 90 RCC cases, the disease-free survival rate was 97.8% (88/90); both the cancer-specific and the overall survival rate were 100%. No death or renal failure after the procedure has yet been found.

CONCLUSIONS

Our results showed that the laparoscopic RFA on small renal mass was safe, with outcomes of patients comparable with those by partial nephrectomy and percutaneous RFA. Further research and a longer follow-up period are needed to confirm our results.

Local thermal ablation of renal cell carcinoma

PURPOSE

With evolving local thermal ablation technology, the clinical application of thermal ablation has been actively investigated in the treatment for renal cell carcinoma. We review the evolution and current status of radiofrequency ablation and microwave ablation for renal cell carcinoma.

MATERIALS AND METHODS

All articles published in English on radiofrequency ablation or microwave ablation as a treatment for renal cell carcinoma were identified with a MEDLINE® and PubMed® search from 1990 to 2010.

RESULTS

Local thermal ablation has several advantages, including keeping more normal renal units, relatively simple operation, easy tolerance, fewer complications, a shorter hospitalization and convalescence period. Long-term data has determined radiofrequency ablation is responsible for poor surgical candidates with renal cell carcinoma, however, tumor size, location and shape might affect the efficacy of radiofrequency ablation. Microwave ablation can induce large ablation volumes and yield good local tumor control. Associated complications appear to be low.

CONCLUSIONS

Local ablative approaches seem to represent an attractive alternative to extirpative surgery for the treatment of small renal neoplasms in select patients. Potential developments include concepts to improve the accuracy and effectiveness of thermal ablation by improving the guiding, monitoring capabilities and detection capacity of multi-center lesions to provide at least equivalent cancer control to conventional surgery.

Thermal ablation of renal cell carcinoma: triage, treatment, and follow-up

The incidence of renal cell carcinoma (RCC) is increasing. With the increasing emphasis on minimally invasive nephron-sparing surgery, thermal ablation is playing a larger role in the management of patients with this disease. This review outlines imaging management, intraoperative and percutaneous ablation, and postprocedural follow-up of RCC.

Adjuvant approaches to enhance cryosurgery

Molecular adjuvants can be used to enhance the natural destructive mechanisms of freezing within tissue. This review discusses their use in the growing field of combinatorial or adjuvant enhanced cryosurgery for a variety of disease conditions. Two important motivations for adjuvant use are: (1) increased control of the local disease in the area of freezing (i.e., reduced local recurrence of disease) and (2) reduced complications due to over-freezing into adjacent tissues (i.e., reduced normal functional tissue destruction near the treatment site). This review starts with a brief overview of cryosurgical technology including probes and cryogens and major mechanisms of cellular, vascular injury and possible immunological effects due to freeze-thaw treatment in vivo. The review then focuses on adjuvants to each of these mechanisms that make the tissue more sensitive to freeze-thaw injury. Four broad classes of adjuvants are discussed including: thermophysical agents (eutectic forming salts and amino acids), chemotherapuetics, vascular agents and immunomodulators. The key issues of selection, timing, dose and delivery of these adjuvants are then elaborated. Finally, work with a particularly promising vascular adjuvant, TNF-alpha, that shows the ability to destroy all cancer within a cryosurgical iceball is highlighted.

The UCI Seldinger technique for percutaneous renal cryoablation: protecting the tract and achieving hemostasis

PURPOSE

To describe our Seldinger technique of percutaneous renal cryoablation that was devised to facilitate renal biopsy, cryoprobe placement, and instillation of adjunctive hemostatics while protecting surrounding tissues from cryoinjury.

PATIENTS AND METHODS

This approach was used to manage 13 renal masses in 12 adult patients. Under CT-fluoroscopic guidance, an access needle was inserted to abut the surface of the tumor, followed by an Amplatz super-stiff guidewire and a customized coaxial catheter system, which was used as a conduit for needle biopsy, cryoprobe insertion, and FloSeal instillation. In addition, a porcine model was used to compare the temperature readings adjacent to the sheathed and the unsheathed cryoprobe during percutaneous renal cryoablation.

RESULTS

In all patients, the use of this access approach was accomplished without incident. Two patients needed blood transfusions. No patient had significant skin, muscle, or nerve debility. At a mean follow-up of 11 months, none had evidence of persistent disease on CT or MRI contrast imaging. In the porcine model, the customized sheath protected the surrounding tissues from reaching temperatures below 5 degrees C while temperatures down to -15 degrees C were obtained when no insulating sheath was used.

CONCLUSIONS

A modified Seldinger technique enabled us to perform percutaneous renal cryotherapy through a single access channel, which facilitated access for biopsy, cryoprobe placement, and instillation of hemostatic agents. This approach may provide a protective barrier against cryogenic damage to neighboring tissues and could theoretically help minimize the chance of tract seeding.

Comparison of Postoperative Pain, Convalescence, and Patient Satisfaction after Laparoscopic and Percutaneous Ablation of Small Renal Masses

PURPOSE

To evaluate the efficacy and safety of rigid ureteroscopy for the treatment ureteral calculi in children.

PATIENTS AND METHODS

Between January 2002 and January 2006, 16 boys and 25 girls with an average age of 9.5 years (range 3-15 years) were treated with a 95F rigid ureteroscope for stones 4 to 10 mm (mean 5.6 mm) in 46 renoureteral units (RUUs), and the results were evaluated. The stones were located in the upper ureter in 4 RUUs, the middle ureter in 15, and the lower ureter in 27. Dilatation of a tight ureteral orifice was necessary in 17 cases (36.9%).

RESULTS

On examination during ureteroscopy, all calculi were well fragmented, and in 33 patients (94%), stone fragments were removed directly. Stones were fragmented with pneumatic lithotripsy in 23 RUUs and removed by forceps with or without fragmentation in the remaining 23. Whereas the treatment was successful in 36 children (87.8%), it was unsuccessful in 5 (12.2%) secondary to bleeding and mucosal injury in 3 children (7%; 1 middle- and 2 upper-ureteral stones) and severe ureteral stenosis with kinking in 2 (4.8%; 1 middle- and 1 upper-ureteral stone) children. In two other cases, although the fragments in the upper portion of the ureter could be reached with the ureteroscope, the stones migrated into the renal collecting system during pneumatic lithotripsy and were treated successfully with subsequent SWL (4.8%). At the end of the procedure, a 4.8F Double-J stent was left in place in 9 cases. There were no serious complications, and the children were not specifically evaluated for postoperative vesicoureteral reflux. Follow-up ranged from 1 to 36 months with an average duration of 22.4 months.

CONCLUSION

With the aid of the experience gained in the adult population and careful instrumentation, we believe that, in skilled hands, rigid ureteroscopy can be applied in a safe and efficient manner for stones located in different portions of the pediatric ureter.

Renal ablation by histotripsy--does it spare the collecting system?

PURPOSE

The feasibility of histotripsy (transcutaneous nonthermal mechanical tissue fractionation) was previously demonstrated in an in vivo rabbit renal cortex model. We explored the spectrum of histotripsy bio-effects on different tissue types in an in vitro porcine kidney model.

MATERIALS AND METHODS

Using an 18 element focused annular array ultrasound system we performed histotripsy treatments in 5 in vitro porcine kidneys, targeting 7 cortical volumes and 17 tissue volumes bridging the cortex, medulla and/or collecting system. Treated areas were observed using ultrasound. In 5 lesions methylene blue was infused into the collecting system to evaluate the preservation of collecting system integrity. Kidneys were sectioned and examined grossly for evidence of tissue fractionation, ie the presence of histotripsy paste, or fixed in formalin and prepared for histological analysis.

RESULTS

Histotripsy of renal cortical tissue created tissue defects in the cortical area treated. Histotripsy targeting the renal collecting system, medulla and renal cortex resulted in tissue fractionation in the area of the cortex, intermediate damage in the medulla and minimal damage to the collecting system.

CONCLUSIONS

There is a differential histotripsy treatment effect when comparing renal cortical tissue to renal collecting system. There is no significant architectural disruption of the renal collecting system after histotripsy. This differential effect is a notable finding that may prove useful in future planning of ablative treatments for renal tissue.

Current practice patterns in the use of ablation technology for the management of small renal masses at academic centers in the United States

OBJECTIVES

To determine the current practice patterns in the use of ablation technology for the management of small renal masses at academic centers in the United States.

METHODS

An email survey was sent to 112 academic urologists subspecializing in minimally invasive management of renal cancer. The survey consisted of 13 questions and 4 clinical scenarios pertaining to the use of ablation technology. The responses were then tabulated and analyzed to determine practice trends.

RESULTS

The overall response rate was 62%. Ablation was offered by 93% of the academic urology centers and cryoablation was more frequently used (79%) than radiofrequency ablation (55%). Lack of sufficient efficacy data was the most prevalent reason (80%) for not offering ablation. The maximum size limit for offering ablation was 4 cm by 55% and 3 cm by 34% of the respondents. A collaborative approach using both radiologist and urologist was most commonly used (51%). Most urologists (68%) used both laparoscopic and percutaneous technique, depending on the tumor and adjacent organ location. Intraoperative ultrasound was universally used during the laparoscopic technique and was usually performed by the urologist (95%). Computed tomographic scan was the most frequently used imaging modality for percutaneous ablation (78%) and for surveillance of recurrent disease (81%). In a younger, healthy patient, most urologists recommend extirpative approach for the management of a small renal mass, whereas laparoscopic-assisted ablation was most commonly recommended for an elderly patient with comorbidities.

CONCLUSIONS

Our survey suggests that laparoscopic and percutaneous ablation is offered by the majority of academic centers for carefully selected patients.

CT and MR imaging after imaging-guided thermal ablation of renal neoplasms

In recent years, thermal tumor ablation techniques such as percutaneous radiofrequency (RF) ablation and cryoablation have assumed an important role in the management of renal tumors, particularly in patients who may be suboptimal candidates for more invasive surgical techniques. Postablation computed tomography (CT) and magnetic resonance (MR) imaging play an important part in evaluation of the ablation zone, surveillance for residual or recurrent tumor, and identification of procedure-related complications. The appearance of the ablation zone may vary depending on the ablation technique used, initial tumor size, and tumor location and composition. Most ablated tumors demonstrate a gradual decrease in size over time once the acute changes have resolved, although tumor involution is more evident after cryoablation than after RF ablation. Exophytic tumor ablation zones typically have a "bull's-eye" appearance on CT scans and MR images obtained after RF ablation, with a visible mass often persisting in the absence of viable tumor. Residual or recurrent tumor often manifests as a focus of nodular or crescentic enhancement on postablation contrast material-enhanced CT scans and MR images, although a thin peripheral rim of enhancement often persists for several months following cryoablation. Complications following renal tumor ablation are usually minor but may include hemorrhage, ureteral stricture, urine leak, colonic perforation and colonephric fistula, and pneumothorax. As more patients undergo renal ablation procedures, it will become increasingly important that radiologists be able to recognize typical postablation CT and MR imaging findings to prevent confusing them with other pathologic processes.

Current Status of Minimally Invasive Ablative Techniques in the Treatment of Small Renal Tumours

OBJECTIVES

In the current era, minimally invasive surgery using ablative techniques for the treatment of small renal tumours has become a more common and feasible treatment option. In this review, we present recent data regarding the utility of needle ablative techniques in the experimental and clinical settings.

METHODS

We performed a comprehensive evaluation of available published data from 1997 to 2006 that were identified with PubMed. Official proceedings of internationally known scientific societies held in the same time period were also assessed.

RESULTS

Two main thermoablative techniques, cryoablation (CA) and radiofrequency ablation (RFA), represent the current available minimally invasive treatments for renal cell carcinoma (RCC). CA has been more extensively studied and has gained acceptance from patients and physicians. The procedure is well tolerated by patients even with serious concomitant diseases. RFA is delivered with a monopolar alternating current. Morbidity rates for this modality remain slightly higher than those for cryotherapy. Both techniques are associated with highly successful cancer control rates at short-to-medium follow-up in patients with tumour size <3 cm. Multiple lesions can be treated simultaneously and the procedures can be repeated. However, long-term follow-up data are still lacking.

CONCLUSION

Minimally invasive ablative approaches seem to represent an attractive alternative to extirpative surgery for the treatment of small renal neoplasms in select patients. Potential developments include concepts to improve the accuracy of thermal ablation using novel imaging modalities with reduction in side-effects and optimised selection and follow-up of patients to provide at least equivalent cancer control to conventional surgery.