Magnetic resonance imaging findings after laparoscopic renal cryoablation

Peri-operative and local control outcomes of robot-assisted partial nephrectomy vs percutaneous cryoablation for renal masses: comparison after matching on radiological stage and renal score

OBJECTIVES

To compare the oncological outcomes of percutaneous cryoablation (PCA) vs robot-assisted partial nephrectomy (RAPN) for the treatment of T1 renal tumours.

PATIENTS AND METHODS

We conducted a retrospective study in all patients treated by RAPN or PCA for malignant renal tumours in one of four centres between 2009 and 2016. Tumours were paired one by one using radiological tumour stage and RENAL nephrometry score (package matchit, R software version 3.2.2). Malignancy was confirmed by biopsy for all patients in the PCA group. Patient characteristics before and after matching and oncological results were compared between the two groups. Cox regression, adjusted for age, treatment type, histological type and margins, was used to identify factors associated with time to local recurrence. Positive margins were defined histologically in the RAPN group and radiologically in the PCA group.

RESULTS

A total of 647 patients were identified; 470 underwent RAPN and 177 underwent PCA. After matching, there was no significant difference between the two groups (RAPN, n = 177; PCA, n = 177) with regard to tumour stage, RENAL nephrometry score, tumour size (27.6 vs 25.9 mm; P = 0.07) and gender ratio. Patients in the PCA group remained significantly older (69.9 vs 59.8 years; P < 0.001). The absolute recurrence rate was 2.8% in the RAPN group vs 8.4% in the PCA group (P = 0.03). The 5-year recurrence-free survival rate was 85% in the PCA group vs 95% in the RAPN group (log-rank P = 0.02). In multivariate analysis, the presence of positive margins and the type of treatment were the two factors significantly associated with local recurrence (P < 0.001 and P = 0.046, respectively).

CONCLUSION

The local recurrence rate after PCA was significantly higher than after RAPN for T1 renal tumours. Incomplete treatment was the main criterion associated with recurrence. The recurrence rate may have been overestimated in the PCA group because of closer radiological follow-up in these patients.

Evolutionary magnetic resonance appearance of renal cell carcinoma after percutaneous cryoablation

Objective:

To determine the evolutionary MRI appearance of renal cell carcinoma (RCC) following cryoablation.

Methods:

For this institution review board-approved study, we recruited patients with biopsy-proven RCC and treated them with percutaneous cryoablation between November 2009 and October 2014. Two radiologists retrospectively reviewed the pre-procedural and follow-up MRI. The findings included tumour sizes, signal intensities on T₁ weighted imaging (T1WI), T₂ weighted imaging (T2WI), diffusion-weighted imaging, apparent diffusion coefficient (ADC) map and contrast enhancement patterns. The ADC values of the tumours before and after treatment were measured.

Results:

A total of 26 patients were enrolled. The ablated tumours exhibited predominantly high signals on T1WI at 1–9-month follow-up (47.1% strong hyperintense at 3 months) and subsequently returned to being isointense. In T2WI, the signals of the ablated tumours were highly variable during the first 3 months and became strikingly hypointense after 6 months (58.3% strong hypointense at 6 months). Diffusion restriction was prominent during the first 3 months (lowest ADC: 0.62 ± 0.29 × 10⁻³ mm² s⁻¹ at 1 month). Contrast enhancement persisted up to 6 months after the procedure. The residual enhancement gradually increased in the dynamic scan and was most prominent in the delay phase.

Conclusion:

The MRI of the cryoablated renal tumour follows a typical evolutionary pattern.

Advances in knowledge:

Familiarity of practitioners with the normal post-cryoablation change of RCC on MRI can enable the early detection and prevention of tumour recurrence.

18F-FDG PET-CT Findings Before and After Laparoscopic Cryoablation of Small Renal Mass: An Initial Report

The aim of this study was to describe the characteristics of positron emission tomography (PET) molecular imaging combined with low-dose computed tomography (CT) in small renal mass (SRM) treated with cryoablation (CA). Currently, treatment success is defined by the absence of contrast enhancement at CT. However, the use of contrast is relatively contraindicated in patients with renal function impairment, mandating alternative follow-up strategies. Several reasons were identified as criteria for performing PET-CT before and/or after SRM-CA in 9 patients, and the results were retrospectively studied. The histology revealed renal cell carcinoma in 7 patients and oncocytoma in 2 patients. In 6 patients, a PET-CT was performed before and after CA. In one patient, the PET-CT was performed only before CA and in 2 patients only after CA. Before CA, clearly there was metabolic uptake of fluorine-18 fluorodeoxyglucose (18F-FDG) in the SRM in all patients. Following CA, the absence of 18F-FDG uptakes in the SRM could clearly be noticed. However, the tracer cannot always be distinguished from focal recurrence or reactive inflammatory tissue. In one patient, asymptomatic metastatic bone lesions were noticed when performing PET-CT at follow-up. This pilot study with 18F-FDG PET-CT for the follow-up of SRM cryosurgery showed that 18F-FDG PET-CT imaging could be used to characterize cryoablative tissue injury at different times after CA.

Renal tissue ablation with irreversible electroporation: preliminary results in a porcine model

OBJECTIVES

To evaluate the histopathologic and computed tomography imaging features associated with irreversible electroporation (IRE) ablation performed in normal porcine kidneys. IRE is a nonthermal ablative tool that uses direct electrical pulses to create permanent "pores" in cell membranes and cell death. It does not affect the extracellular matrix.

METHODS

Fifteen female swine were treated with IRE using acute (<24 hours), subacute (36 hours), and chronic (3 weeks) treatment settings. Unipolar IRE applicators were placed under CT guidance. The renal pelvis/calyx was included in 18 ablations. Imaging and histopathologic follow-up were performed.

RESULTS

A total of 29 ablations (19 acute, 4 subacute, and 6 chronic) were created. Acute/subacute ablations showed complete cortical necrosis without intervening live cells. The pelvic epithelium was necrotic with urothelial sloughing; pelvic extracellular matrix was intact. Chronic ablations showed cortical fibrosis, regenerating renal pelvic epithelium and intact pelvic extracellular matrix. No thermal injury, renal pelvic, or blood vessel injury was seen. Immediate postprocedure CT imaging demonstrated a hypodense nonenhancing lesion that persisted at 1 week. Of the 6 chronic lesions, 4 showed complete resolution at 3 weeks on imaging. No collecting system damage was seen.

CONCLUSIONS

This preliminary porcine study demonstrates the nonthermal and connective tissue sparing mechanism of action of IRE. These features may protect against collecting system damage after IRE ablation of renal tissue. IRE could therefore play an important role in ablation of centrally located renal tumors.

Comparison of gadoxetic acid-enhanced MR imaging versus four-phase multi-detector row computed tomography in assessing tumor regression after radiofrequency ablation in subjects with hepatocellular carcinomas

PURPOSE

To assess the diagnostic value of gadoxetic acid-enhanced magnetic resonance (MR) imaging in follow-up of patients with hepatocellular carcinomas (HCCs) who were treated with radiofrequency (RF) ablation and to compare it with that of four-phase multi-detector row computed tomography (CT).

MATERIALS AND METHODS

From July 2007 to May 2008, 36 patients (43 HCCs) were enrolled who were treated with RF ablation (tumor size, 20-47 mm; mean, 24.5 mm) and underwent gadoxetic acid-enhanced MR imaging and four-phase (precontrast, arterial, portal venous, and equilibrium) multidetector CT for follow-up. Two radiologists independently reviewed these images, and conspicuity of tumor margins and detection of residual or recurrent tumor were assessed on a five-point scale with receiver operating characteristic (ROC) curve analysis. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were evaluated.

RESULTS

The mean conspicuity value of tumor margins was significantly higher on MR imaging than on multidetector CT (P < .001). The degree of differentiation between residual/recurrent tumor and hyperemia was significantly greater on MR imaging (P < .001). The mean area under the ROC curve was significantly higher with MR imaging (P = .015), as were sensitivity, specificity, PPV, NPV, and accuracy of detection rate (mean, 100%, 96.2%, 82.4%, 100%, and 96.7%, respectively, vs 41.7%, 56.8%, 13.5%, 85.7%, and 54.7% for multidetector CT). The interobserver agreement rate for MR imaging was higher (0.919) than for multidetector CT (0.672; P < .05).

CONCLUSIONS

Diagnostic accuracy, conspicuity of tumor margins, and detection rate of residual or recurrent tumor were found to be better with gadoxetic acid-enhanced MR imaging than with four-phase multidetector CT.

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.

Feasibility study on using an infrared thermometer for evaluation and administration of cryosurgery

Successful performance of cryosurgery relies heavily on a quick, efficient, safe and economic imaging way to monitor the surgical advancement and then to evaluate the curative effect. However, there is currently a lack of such an imaging modality. As for the commonly adopted imaging devices such as X-CT, MRI and PET, in addition their high cost and complexity in operation, they often induce additional scathe to the patients due to their potential radiation effects. Besides, in cryosurgery, the most important parameter - temperature - can not be directly detected by these methods. Considering the above factors, infrared thermography (IRT), a rather useful yet often neglected functional imaging technique in clinics, is proposed in this paper as an efficient tool for the quick evaluation and administration of a cryosurgical treatment of tumors. Based on skin surface temperature mapping, the degree of damage to the target tissue site caused by different freezing/heating protocols, as well as the states of blood circulation and metabolic heat generation within the treated region can possibly be identified. Further, through recording the temperature variation feature at the skin surface before and after cryosurgery, IRT would help to quickly evaluate the curative effect, which is very beneficial for later treatment planning. By detecting the surface infrared image and analyzing its digital values, the patient's invisible focus and abnormal physiological states, e.g. inflammations or pneumothorax, often accompanied by cryosurgical output yet difficult to determine via conventional imaging, could also possibly be diagnosed. To test the above concepts, both typical animal and clinical experiments were performed to demonstrate the feasibility and advantages of IRT-guided cryosurgery. This study may help push forward a novel, low-cost and non-contact way for an efficient performance of cryosurgery.

Contrast-enhanced ultrasonography in the follow-up of cryoablation of renal tumours: a feasibility study

OBJECTIVE

To determine whether evaluating perfusion patterns with contrast-enhanced ultrasonography using contrast-pulse sequence imaging (CPS; a new imaging method that enables selective visualization of perfusion) is possible at different times after cryoablation of renal tumours, and to describe the characteristics of CPS in a small group of patients.

PATIENTS AND METHODS

The efficacy of renal cryoablation is mainly judged using imaging. Seven randomly selected patients, each at a different time after laparoscopically assisted cryoablation of a renal tumour, were investigated with CPS and a microbubble-contrast agent. The perfusion characteristics in the lesions were scored by two investigators and described, and the lesions were measured.

RESULTS

In the seven patients treated with cryoablation for small renal tumours, eight CPS studies were performed. Five lesions showed no enhancement and one lesion, investigated 18 months after treatment was not recognized. In one patient, no enhancement was seen after 1 month but 7 months later, there were minimal contrast signals inside the treated area. The lesions could be measured with a mean standard deviation of 1.1 mm and a mean difference between the two investigators of 0.7 mm.

CONCLUSION

Our first experiences with CPS imaging for the follow-up of renal cryoablation show that this technique can be used to characterize perfusion defects at different times after cryoablation.

Oncologic outcomes for ablative therapy of kidney cancer

Needle ablative therapies for small incidental renal masses are emerging as alternatives to traditional extirpative surgery. Reasons include their associated decreased morbidity, shorter convalescence, and the ability to avert the higher risk of extirpative surgery in an aging patient population. Cryoablation (CA) and radiofrequency ablation are the two most thoroughly studied needle ablative methods used for renal cancer. High-intensity focused ultrasound has also been studied but with limited published human experience at this time. For both radiofrequency ablation and CA, in vitro experiments, animal studies, and (increasingly) human experience have been published, allowing us to define appropriate candidates for such therapies, their oncologic outcomes, and the potential pitfalls. While long-term data is being collected, the current literature suggests that CA and radiofrequency ablation can be safely performed and can effectively eradicate small renal cancers with cancer-specific survival rates similar to those of traditional surgical options.

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.

Energy ablative techniques for treatment of small renal tumors

PURPOSE OF REVIEW

The success of partial nephrectomy for the treatment of small renal cancers has led to the development of energy ablative technologies, which are less invasive alternatives for performing nephron-sparing surgery. Currently, cryoablation and radiofrequency ablation are the two most reported technologies. Both technologies use very different means to cause cellular injury. Additionally, three newer technologies, high-frequency ultrasound ablation, laser interstitial therapy, and microwave therapy are emerging in the literature.

RECENT FINDINGS

Three- and 4-year data for cryoablation and radiofrequency ablation are now becoming available. On the basis of these studies, it is clear that ablative technologies can be effective treatments for select small renal tumors. It is also evident that both percutaneous and laparoscopic approaches offer minimal morbidity.

SUMMARY

As long-term (5 years and greater) outcome data for ablative technologies accumulate, we are likely to see an increase in clinical reports, including more patients who may be candidates for extirpative surgery. Technology will advance, leading to smaller probes with larger treatment zones, making it possible to treat larger tumors and potentially even tumors in the advanced disease state.