Thermal Ablation of Renal Tumors: Indications, Techniques and Results

Characterization of Ferromagnetic Composite Implants for Tumor Bed Hyperthermia

Hyperthermia therapy (HT) is becoming a well-recognized method for the treatment of cancer when combined with radiation or chemotherapy. There are many ways to heat a tumor and the optimum approach depends on the treatment site. This study investigates a composite ferromagnetic surgical implant inserted in a tumor bed for the delivery of local HT. Heating of the implant is achieved by inductively coupling energy from an external magnetic field of sub-megahertz frequency. Implants are formed by mechanically filling a resected tumor bed with self-polymerizing plastic mass mixed with small ferromagnetic thermoseeds. Model implants were manufactured and then heated in a 35 cm diameter induction coil of our own design. Experimental results showed that implants were easily heated to temperatures that allow either traditional HT (39-45°C) or thermal ablation therapy (>50°C) in an external magnetic field with a frequency of 90 kHz and amplitude not exceeding 4 kA/m. These results agreed well with a numerical solution of combined electromagnetic and heat transfer equations solved using the finite element method.

Active surveillance and focal ablation for small renal masses: a better solution for comorbid patients

The natural history of small renal masses (SRM) is still not well understood and they are frequently incidentally diagnosed in elderly patients. Therefore, there is a need for less invasive options sparing the patient from the side-effects related to conventional surgical treatment. PubMed and Medline database search was performed to look for new findings on active surveillance and focal therapy for SRM. Sixty-one articles published between 2002 and 2018 were selected for the purpose of the review. There is growing evidence confirming the safety of active surveillance in patients at surgical risk and there appears to be a satisfactory intermediate-term outcome of focal treatment of SRM. In the group of elderly patients with a decreased life expectancy active surveillance appears to be the most appropriate approach. The future of minimally invasive therapy appears bright, especially with the improvement of new imaging modalities.

Percutaneous image-guided ablation: From techniques to treatments

Image-guided ablation is performed by percutaneously introducing ablation probes to deliver energy into a tumor to destroy it in a controlled and localized fashion. Ablation modalities can be broadly classified as thermal or non-thermal based on the mechanism of tumor destruction and are performed using different types of image guidance for planning, delivering and follow-up of the treatment. Ablation is performed in a minimally invasive fashion, providing greater residual organ preservation with minimal morbidity to the patient. Image-guided ablation is being used in the clinic for the treatment of primary and metastatic tumors, and this article reviews state of the art for the treatment of malignancies in the liver, lung, kidney and musculoskeletal tissue.

[Ablative therapy of small renal masses]

Renal cell cancer is nowadays predominantly diagnosed in early stages due to the widespread use of sectional imaging for unrelated symptoms. Small renal masses (<4 cm) feature a largely indolent biology with a very low risk for metastasis or even a benign biology in up to 30% of the cases. Consequently, there is a need for less invasive therapeutic alternatives to nephron-sparing surgery. Meanwhile, there is a broad portfolio of local ablation techniques to treat small renal tumors. These include the extensively studied radiofrequency ablation and cryoablation techniques as well as newer modalities like microwave ablation and irreversible electroporation as more experimental techniques. Tumor ablation can be performed percutaneously under image guidance or laparoscopically. In particular, the percutaneous approach is a less invasive alternative to nephron-sparing surgery with lower risk for complications. Comparative studies and meta-analyses report a higher risk for local recurrence after renal tumor ablation compared to surgery. However, long-term oncological results after treatment of small renal masses are promising and do not seem to differ from partial nephrectomy. The possibility for salvage therapy in case of recurrence also accounts for this finding. Especially old patients with an increased risk of surgical and anesthesiological complications as well as patients with recurrent and multiple hereditary renal cell carcinomas may benefit from tumor ablation. Tumor biopsy prior to intervention is associated with very low morbidity rates and is oncologically safe. It can help to assess the biology of the renal mass and prevent therapy of benign lesions.

Ex vivo human bile duct radiofrequency ablation with a bipolar catheter

BACKGROUND

Management of the primary and secondary tumors of the bile ducts still remains as a major clinical challenge. Radiofrequency (RF) ablation (RFA) of these tumors is feasible but the effect of RF energy on the human common bile duct (CBD) and surrounding tissues has not been investigated. This pilot study aimed to determine the relationship between RF energy and the depth of ablation in the normal human CBD.

METHODS

The study was performed on fresh ex vivo human biliary-pancreatic tissue which had been resected for a pancreatic cyst or mass. The study was conducted within 15 min after resection. A bipolar Habib RFA catheter was placed into the middle of the intact CBD, and three different (5, 7, 10 W) power settings were applied over a 90-s period by an RF generator. Gross and histological examinations were performed. The depth of coagulation necrosis in CBD and the effect of RFA on CBD wall and surrounding pancreas tissue were determined by microscopic examination.

RESULTS

The study included eight tissue samples. 5 W power was applied to three sites and RFA caused only focal epithelial necrosis limited to the CBD mucosa. 7 and 10 W were applied to five sites and coagulation necrosis occurred in all cases. Microscopically, necrosis was transmural, involved accessory bile duct glands, and extended to the surrounding pancreatic tissue in four of these cases. Macroscopically, RFA resulted in circumferential white-yellowish color change extending approximately 2 cm of the CBD.

CONCLUSION

Bipolar RF energy application with 5 W resulted in limited ablation on CBD wall. However, 7 and 10 W generated tissue necrosis which extended through the CBD wall and into surrounding pancreas tissue. Endoscopic biliary RFA is an effective technique for local biliary tissue ablation but the use of high energy may injure surrounding tissue.

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.

Management of Urinoma Formation After Laparoscopic Cryoablation of Renal Cyst

Aim: To describe the presentation and management of a urinoma developing as a complication of laparoscopic cryoablation of a Bosniak III renal cyst.

Case: A 74-year-old woman presented with acute onset of severe left lower abdominal pain 1 day after a laparoscopic cryoablation of a 3 cm multilobular left cystic renal mass. CT revealed a perinephric fluid collection adjacent to the lower pole of the left kidney with active urinary extravasation seen on retrograde pyelogram, confirming the presence of an urinoma. A retrograde ureteral stent was placed with complete resolution of symptoms and the patient was discharged on the first postoperative day. Follow-up CT scans 2 weeks and 2 months after the procedure showed significant reduction of urinoma size, and retrograde pyelogram 5 months after showed resolution of urinoma.

Conclusion: Although often discussed as a possible complication, to our knowledge there are no published case reports in the literature regarding the formation of a urinoma after laparoscopic cryoablation. Furthermore, no data exist on the management of a urinoma after laparoscopic cryoablation. We propose that ureteral stenting is a reasonable approach to the management of this condition.

Small renal masses in the elderly: Contemporary treatment approaches and comparative oncological outcomes of nonsurgical and surgical strategies

Over the last decades, there has been a significant stage migration in renal cell carcinoma and especially older patients are getting diagnosed more frequently with low stage disease, such as small renal masses ≤4 cm of size. Considering the particular risk profile of an older population, often presenting with a nonnegligible comorbidity profile and progressive renal dysfunction, treatment approaches beyond aggressive radical surgical procedures have come to the fore. We sought to give a contemporary overview of the available different treatment strategies for incidental small renal masses in an elderly population with the focus on comparative oncological outcomes of nonsurgical and surgical modalities.