Imaging Associated with Percutaneous and Intraoperative Management of Renal Tumors

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.

Magnetic resonance imaging-navigated argon-helium cryoablation therapy against a rabbit VX2 brain tumor

The aim of the present study was to investigate the feasibility of interventional magnetic resonance imaging (MRI)-guided and monitored argon-helium cryoablation for the treatment of brain tumors in rabbits. In addition, the present study evaluated the associations between imaging and pathology, the therapeutic effects and the effects on the surrounding normal tissues. A total of 14 rabbits were equally divided into groups C and D. Under general anesthesia, the skull was drilled and tumor blocks were implanted. Subsequently, a New Zealand rabbit VX2 brain tumor model was successfully established. Rabbits in group C were treated with argon-helium cryoablation and those in group D did not undergo any treatment (control). Regular postoperative MRI scanning was performed to observe the changes in tumor size, and the survival times of the rabbits in groups C and D were recorded. The extent of necrosis in the brain tumor exhibited a significant correlation with the freezing time of cryoablation, and the necrotic region was shown to be the same size as the ice ball. The survival times of the rabbits in the treatment group (group C) were significantly prolonged. Therefore, the observations of the present study demonstrated that the VX2 brain tumor model, produced using an improved tumor block implantation method, was stable and suitable for MRI observation and interventional study. In addition, argon-helium cryoablation was shown to be a safe and feasible therapeutic method for the treatment of brain tumors, and was demonstrated to significantly increase the survival times of the brain tumor-bearing rabbits.

Immediate effect of kidney cryoablation on renal arterial structure in a porcine model studied by imaging cryomicrotome

PURPOSE

Injury to blood microvessels has a crucial role in effective cryoablation for renal masses. We visualized vascular injury induced by a clinically applied cryoablation instrument and established a microvascular diameter threshold for vascular damage.

MATERIALS AND METHODS

In 5 anesthetized pigs 1 kidney each was exposed and 3, 17 gauge cryoneedles were inserted in 1 pole. Tissue was exposed to freezing for 2 x 10 minutes with a 10-minute thaw between freezes. After nephrectomy the arteries were injected with fluorescence dyed casting material and the kidney was frozen to -20C and cut in 40 to 60 micron slices in the imaging cryomicrotome, where fluorescent images of the cutting plane of the bulk were obtained. This resulted in a 3-dimensional image of the arterial tree that was segmented, resulting in unbranched vessel segments. Histograms were constructed with the total segment length per diameter bin plotted as function of diameter.

RESULTS

The ablated zone was sharply demarcated on fluorescent and normal light images. Mean +/- SD diameter at the peak of the histogram from control areas was 152.4 +/- 5.3 micron. Compared to control areas the peak diameter of ablated areas was shifted to a larger diameter by an average of 25.4 +/- 2.6 micron.

CONCLUSIONS

Immediate renal cryoablation injury destroys arteries smaller than 180 micron. Branching structures of larger arteries remain anatomically intact and connected to vascular structures in surrounding tissue.

Management of renal masses with laparoscopic-guided radiofrequency ablation versus laparoscopic partial nephrectomy

BACKGROUND AND PURPOSE

Laparoscopic-guided radiofrequency ablation (LRFA) has been introduced as a minimally invasive nephron-sparing management option for renal tumors. Many patients who desire treatment present with multiple comorbidities, which poses a therapeutic challenge. Our purpose is to determine if multipass LRFA is comparable, in terms of surgical risk and immediate postoperative outcomes, to laparoscopic partial nephrectomy (LPN).

PATIENTS AND METHODS

A retrospective study identified 36 and 33 patients who underwent LRFA and LPN, respectively. Perioperative demographic data, tumor characteristics, and follow-up data were evaluated. Statistical analysis was performed using the Student t test and chi-square analysis.

RESULTS

Age, American Society of Anesthesiology score, and Charlson Comorbidity Index were significantly higher in the LRFA group than the LPN group (P < 0.001). Average tumor size was 2.8 cm and 3.1 cm for the LRFA and LPN groups, respectively. There were no significant differences in change between the preoperative and postoperative creatinine/glomerular filtration rate values or perioperative complication rates for the groups. Estimated blood loss and length of stay were significantly lower for the LRFA group than the LPN group (P < 0.05). Follow-up ranged 6 to 23 months and 6 to 58 months for the LRFA and the LPN groups, respectively. There has been no evidence of tumor recurrence in the follow-up period.

CONCLUSIONS

We present our initial report comparing patients undergoing LRFA v LPN for the management of renal tumors. Our preliminary results with our experience with multipass laparoscopic-guided RFA demonstrate that this technique can be safely used in an elderly, higher risk population. Long-term follow-up is needed to determine oncologic efficacy.

Radiologic evaluation of small renal masses (II): posttreatment management

The increase in the detection of small renal masses (SRMs) and their best knowledge leads to a change in the therapeutic management of these lesions. The use of a less aggressive surgical technique or even an expectant attitude is the current tendency, in order to preserve as much renal function as possible. Imaging techniques are essential in the followup of these lesions. It allows us to know the postsurgical changes and possible complications due to treatment and the presence of local recurrence and metastases. Furthermore, a close radiological followup of SRM related to ablative treatments is mandatory. The purpose of this article is to reveal the imaging features of complications due to surgical or ablative treatments, local recurrence and metastasis, as well as their followup.

Ablative techniques for the management of kidney cancer

For lesions smaller than 4 cm, nephron-sparing surgery has been shown to be oncologically equivalent to radical nephrectomy, albeit with the advantage of preservation of overall renal function. As such, partial nephrectomy became the first-line treatment option for localized, small renal masses. Minimally invasive options associated with limited morbidity--such as probe-ablative procedures--are, however, being investigated in selected patients for whom invasive, nephron-sparing surgery (whether laparoscopic or open) is undesirable. The main probe-ablative techniques being investigated as alternatives to partial nephrectomy are cryoablation, radiofrequency ablation, and high-intensity focused ultrasound. Advances in imaging, ablative system technologies, and early evidence that in situ tumor ablation can yield comparable results to those achieved with tumor resection in selected cases, have sparked significant interest in these minimally invasive techniques.