Microwave ablation of renal tumors: state of the art and development trends

Comparison of the Efficacy of Percutaneous Microwave Ablation Therapy versus Laparoscopic Partial Nephrectomy for Early-Stage Renal Tumors

This study aimed to compare the efficacy of percutaneous microwave ablation therapy (MWAT) and laparoscopic partial nephrectomy (LPN) in early-stage renal cell carcinoma (RCC) classified as T1a; a retrospective analysis was conducted on patients treated between January 2017 and November 2023. Oncological outcomes, radiological recurrence, length of stay (LOS), and costs were evaluated. The study included 110 patients, with no significant differences between the two groups regarding residual tumors, local tumor progression, and disease-free survival rates (p > 0.05). The LPN group showed significantly lower pre/postoperative serum urea and creatinine and higher estimated glomerular filtration rate values, whereas the MWA group experienced significantly lower mean costs, complication rates, LOS in the hospital, and procedure durations (p ≤ 0.05). However, post-procedure residual tumors and local tumor progression rates did not differ significantly between the LPN and MWAT groups (p > 0.05). MWAT is as effective as LPN for T1a RCC lesions. In addition, MWAT has lower costs than LPN and is a cost-effective treatment method. Therefore, MWAT minimizes hospital stay and complications and since the oncological results are similar to LPN, it might be considered as the first choice of treatment in young patients.

Locoregional Therapies and Remodeling of Tumor Microenvironment in Pancreatic Cancer

Despite the advances made in treatment, the prognosis of pancreatic ductal adenocarcinoma (PDAC) remains dismal, even in the locoregional and locally advanced stages, with high relapse rates after surgery. PDAC exhibits a chemoresistant and immunosuppressive phenotype, and the tumor microenvironment (TME) surrounding cancer cells actively participates in creating a stromal barrier to chemotherapy and an immunosuppressive environment. Recently, there has been an increasing use of interventional radiology techniques for the treatment of PDAC, although they do not represent a standard of care and are not included in clinical guidelines. Local approaches such as radiation therapy, hyperthermia, microwave or radiofrequency ablation, irreversible electroporation and high-intensity focused ultrasound exert their action on the tumor tissue, altering the composition and structure of TME and potentially enhancing the action of chemotherapy. Moreover, their action can increase antigen release and presentation with T-cell activation and reduction tumor-induced immune suppression. This review summarizes the current evidence on locoregional therapies in PDAC and their effect on remodeling TME to make it more susceptible to the action of antitumor agents.

Effects of microwave ablation on cysts and cystic neoplasms with tissue-mimicking model: an ex vivo study

BACKGROUND AND PURPOSE

Microwave ablation (MWA) is a promising modality that needs to be further investigated for cystic lesions. The present study aimed to determine the effects of MWA on cysts and cystic neoplasms with a tissue-mimicking model.

METHODS

Twenty New Zealand White rabbits were randomly divided into Group A (cyst mimic models, n = 10, φ = 5 cm) and Group B (cystic neoplasm mimicking models, n = 10, φ = 5 cm). For each group, ex vivo rabbit healthy bladder and VX2-implanted tumor bladder were fixed and embedded in agarose gel to mimic cyst and cystic neoplasm. In the MWA experimental subgroups, microwave antennas guided by computed tomography (CT) were introduced into these models. A system thermometer was placed at the outer edge of the bladder wall to monitor temperature changes. Immediately after MWA, ex vivo rabbit healthy bladders and VX2-implanted tumor bladders were harvested for gross anatomy and prepared for pathological evaluation.

RESULTS

A total of twenty cyst and cystic neoplasm mimicking models were successfully developed. Ninety percent of the MWA procedures were successful, and no peri-procedural complications were encountered. The temperature of the cystic wall increased with duration in both MWA experimental subgroups and an effective ablation temperature (>60 °C) was achieved. Pathological examination of the cyst and cystic neoplasm mimic models revealed degenerative necrosis of the bladder wall mucosal epithelial cells, loss of bladder wall tissue structure and coagulative necrosis of VX2 tumor cells.

CONCLUSION

Our data indicate that MWA could cause thermal damage to the tissue structure of cyst and cystic neoplasm, and it is an effective technique for treating cystic diseases.HIGHLIGHTSex vivo rabbit healthy bladder and VX2-implanted tumor bladder were fixed and embedded in agarose gel to mimic cyst and cystic neoplasm.The temperature of the cystic wall increased with MWA duration and an effective ablation temperature (> 60 °C) was achieved.MWA could cause thermal damage to the tissue structure of the cyst and cystic neoplasm and it is effective in treating cystic diseases, as assessed by histopathology.

Clinical Study on the Efficacy of Microwave Ablation (MA) in the Treatment of Stage I Renal Clear Cell Carcinoma by CT and MRI Imaging

We have proposed an effective mechanism to corroborate the efficacy of microwave ablation (MA) in the treatment of stage I renal clear cell carcinoma in this paper. For this purpose, a total of 96 patients with stage I renal clear cell carcinoma presented in our hospital from May 2018 to January 2021 were randomly divided into CT group (n = 48) and MRI group (n = 48). Patients in both groups were treated with microwave ablation after pathological diagnosis. Patients in the CT group received enhanced CT examination to monitor the therapeutic effect; in contrast, patients in the MRI group received MRI examination to monitor their therapeutic effect. The focus areas before and after tumor microwave ablation were compared between the two groups. The patients were followed up to 1 year after the operation, and the microwave ablation inactivation rates of the two groups were compared according to the postoperative follow-up results. There was no significant difference between CT and MRI in the levels of long and short diameter before and after microwave ablation of renal clear cell carcinoma (P > 0.05). In the CT group, CT examination was performed within 24 hours after microwave ablation treatment, and 44 of 48 ablation lesions showed complete ablation. The remaining 4 lesions showed nodular heterogeneous enhancement in the arterial phase, indicating that the tumor remained. Microwave ablation was performed on the residual lesions during the operation, and then enhanced CT was performed again to show that the lesions were ablated completely. In the MRI group, MRI examination was performed within 24 hours after microwave ablation treatment, and 45 of 48 ablation lesions showed complete ablation. The remaining 3 lesions showed nodular heterogeneous enhancement in the arterial phase, indicating that the tumor remained. Microwave ablation was performed on the residual lesions during the operation, and MRI examination showed that the lesions were ablated completely. The patients were followed up to 1 year after the operation, and the microwave ablation inactivation rate of the two groups was compared according to the postoperative follow-up results as the gold standard. The inactivation rate of microwave ablation in the CT group was 89.58 (43/48). The inactivation rate of microwave ablation in the MRI group was 100.00% (48/48). The inactivation rate of microwave ablation in the MRI group was higher than that in the CT group (χ² = 5.275, P = 0.021).

Use of percutaneous microwave ablation in the treatment of retroperitoneal neoplasia in three dogs

CASE DESCRIPTION

3 dogs with retroperitoneal masses (2 renal and 1 located near the diaphragm) were treated by percutaneous microwave ablation (MWA).

CLINICAL FINDINGS

Dogs between 11 and 13 years of age weighing between 13.7 and 43.8 kg had either a renal mass (n = 2) or a mass located in the caudodorsal aspect of the retroperitoneal space near the right side of the diaphragm (1). Cytology revealed that one of the renal masses and the mass located near the diaphragm were malignant neoplasias. Findings on cytologic evaluation of a sample of the other renal mass was nondiagnostic. Maximum mass diameters ranged between 1.4 and 2.5 cm.

TREATMENT AND OUTCOME

All dogs were treated by percutaneous MWA. Probes were directed into tumors by use of ultrasound and CT guidance, and microwave energy was applied to each mass. Findings on imaging of each mass following MWA was consistent with successful treatment. No intraprocedural or major postprocedural complications occurred, and all dogs were discharged from the hospital within 3 days of treatment. Two dogs died at 3 and 21 months after MWA with no known local recurrence; 1 dog was still alive 64 months after treatment.

CLINICAL RELEVANCE

Although the indications for MWA in the treatment of neoplasia in companion animals are limited, the outcomes of dogs in the present report provided preliminary evidence that percutaneous MWA can be safely used to effectively treat retroperitoneal neoplasia. This procedure was successfully performed with image guidance in all 3 dogs.

Efficacy and safety of CT-guided microwave ablation for stage T1a renal cell carcinoma in patients with a solitary kidney

OBJECTIVE

To retrospectively evaluate early clinical outcomes of percutaneous microwave ablation (MWA) for stage T1a renal cell carcinomas (RCCs) in solitary kidney patients.

MATERIALS AND METHODS

15 solitary kidney patients with 16 stage T1a N0M0 biopsy-proved RCCs underwent CT-guided percutaneous microwave ablation between October 2016 and July 2020. The patients were followed up with contrast-enhanced computed tomography or magnetic resonance imaging at 1, 3, and 6 months and every 6 months thereafter. Serum creatinine levels of each patient pre MWA, 1 day after MWA and the most recent record were collected. Technical effectiveness, local recurrence, survival rates and complications were accessed.

RESULTS

Complete ablation was achieved in all 16 tumors (100%) including 13 clear cell carcinomas and 3 papillary carcinomas. Within the follow-up time (median: 24 months) no tumor recurrence or major complication was detected. No significant change in serum creatinine level was noted. The cancer-specific survival rate was 100% (15 of 15), and 1-, 2-, and 3-year overall survival rates were 100%, 93.3%, and 93.3%, respectively.

CONCLUSION

Percutaneous MWA is an effective and safe treatment option for stage T1a RCCs in solitary kidney patients; it can achieve high complete ablation rate in selected lesions of appropriate size and location.

Percutaneous microwave ablation of renal cell carcinoma: practice guidelines of the ultrasound committee of Chinese medical association, interventional oncology committee of Chinese research hospital association

Imaging-guided percutaneous microwave ablation (MWA) with high thermal efficiency comprises rapid, successful management of small renal cell carcinomas (RCCs) in selected patients. Ultrasound Committee of Chinese Medical Association, Interventional Oncology Committee of Chinese Research Hospital Association developed evidence-based guidelines for MWA of RCCs after systematically reviewing the 1969-2019 literature. Systematic reviews, meta-analyses, randomized controlled trials, cohort, and case-control studies reporting MWA of RCCs were included and levels of evidence assessed. Altogether, 146 articles were identified, of which 35 reported percutaneous MWA for T1a RCCs and 5 articles for T1b RCCs. Guidelines were established based on indications, techniques, safety, and effectiveness of MWA for RCCs, with the goal of standardizing imaging-guided percutaneous MWA treatment of RCCs. Key points Microwave ablation is recommended for managing small renal cell carcinoma in selected patients. Imaging protocols are tailored based on the procedural plan, guidance, and evaluation. Patient's selection evaluation, updated technique information, clinical efficacy, and complications are recommended to standardize management. A joint task force (multidisciplinary team) summarized the key elements of the standardized report.

The feasibility of intranasal endoscopic microwave ablation on the removal of nasolabial cyst: Preliminary case series

OBJECTIVE

The aim of this study was to investigate the clinical effect of the removal of nasolabial cyst via intranasal endoscopic microwave ablation (MWA).

METHODS AND MATERIALS

The patients with nasolabial cyst were ablated through intranasal endoscopic MWA. Postoperative pain intensity was measured via visual analogue scale (VAS), post-operative complications were recorded.

RESULTS

Of the 31 patients with unilateral nasolabial cyst, the main complaint was a gradually increasing mass in the nasal alar and upper lip, other complaint included nasal obstruction (11/31,35.5%), localized pain (21,67.7%), and erythema (13/31,41.9%). All 31 patients were successfully treated with the intranasal endoscopic ablation technique in outpatient. The mean ablation duration was 5.86 ± 0.71 min. The mean VAS pain score was 2.36 ± 1.08 on postoperative. None of infection occurred. All the patients complained of mild numbness in the upper lip with an average last duration of 28.5 ± 7.9 h in patients. In addition, 4 (12.9%) patients had facial/perinasal swelling, acid bilge of maxillary teeth in 7(22.6%), and toothache in one (3.2%). The patients were followed up for 12 months without recurrence and oronasal fistula. The nasolabial cyst had integrated into a part of the nasal cavity.

CONCLUSIONS

The intranasal endoscopic MWA is feasible and alternative to conventional transoral sublabial approach for removal of the nasolabial cysts in outpatient.

Percutaneous Thermal Ablation for Treatment of T1a Renal Cell Carcinomas

Based on Surveillance, Epidemiology, and End Results studies, most renal cancers are low grade and slow growing. Long-term, single-center studies show excellent outcomes for T1a renal cell carcinoma (RCC), comparable to partial nephrectomy without affecting renal function and with much lower rates of complications. However, there are no multicenter randomized controlled trials of multiple ablative modalities or comparison with partial nephrectomy, and most studies are single-arm observational studies with short-term and intermediate follow-up. For treatment of stage T1a RCC, percutaneous TA is an effective alternative to surgery with preservation of renal function, low risk, and comparable overall and disease-specific survival.

Radiofrequency ablation (RFA) of T1a renal cancer with externally cooled multitined expandable electrodes

INTRODUCTION

To retrospectively evaluate the mid-term outcomes of percutaneous radiofrequency ablation (RFA) with multitined expandable electrodes externally cooled with saline solution in patients with T1a renal cell carcinoma (RCC).

MATERIALS AND METHODS

In this retrospective study, we evaluated 39 RCC in 35 patients treated with CT-guided RFA in 41 procedures (2011-2017). All patients were staged T1a, N0, M0 prior to RFA. Mean tumor size was 24.48 mm. A 4-tined expandable RFA electrode cooled with pump-circulating saline was used. Efficacy was evaluated verifying complete tumor necrosis (no contrast enhancement on imaging) at the end of the procedure and on subsequent controls. Follow-up observation period was 5 years. Minor/major complications, hospitalization days, serum creatinine and GFR pre- and post-RFA (compared using paired t test) and post-operative pain (evaluated with NRS after treatment) were considered as safety indicators. Overall survival was also calculated (Kaplan-Meier method).

RESULTS

Of 35 patients, 30/35 had 1 treatment (primary effectiveness rate 86%), 4/35 had 2 treatments and 1/35 had 3 treatments for residual disease. There were no relapses and no mid-long-term complications; 3 minor (8%) and 1 major (2.7%) complications during perioperative period were reported. Mean before and after RFA serum creatinine rates were, respectively, 1.08 mg/dl and 1.11 mg/dl (p value: 0.4117). NRS median value is 0.8. Hospitalization days median value is [2.8 ± 1.9] days. 91.4% of all patients survived, with a median overall survival time of 65 months.

CONCLUSIONS

Mid-term results show that CT-guided RFA with multitined expandable electrodes externally cooled with saline solution is an effective and safe treatment in patients with RCC-staged T1aN0M0. Data reported in our study are in line with data reported in the literature from patients treated with other devices.

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.

Safety and efficacy of percutaneous microwave ablation for post-procedural haemostasis: a bi-central retrospective study focusing on safety and efficacy

OBJECTIVE

To review safety and efficacy of percutaneous microwave ablation (MWA) for post-procedural haemostasis.

METHODS

Institutional databases retrospective research identified 10 cases of iatrogenic bleeding who underwent percutaneous MWA for post-procedural haemostasis. Ultrasound examination with Doppler and contrast enhancement identified a source of active bleeding prior to ablation; additionally they were used as guiding modality for antenna insertion whilst, post-ablation, assessed the lack of active extravasation. Target locations included liver intercostal space spleen and thyroid gland. Technical success was defined as positioning of the antenna on the desired location. Treatment end point was considered the disappearance of active extravasation in both Doppler imaging and contrast-enhanced ultrasound.

RESULTS

Technical success (i.e. positioning of the antenna on the desired location) was achieved in all cases. No complications were noted. All patients post MWA remained haemodynamically stable with no need for transfusion and were discharged from the hospital the next morning. Imaging and clinical follow-up in all patients before exiting the hospital did not depict any sign of active extravasation or bleeding.

CONCLUSION

Our limited experience reports preliminary data showing that MWA could be added in the armamentarium of percutaneous therapies for iatrogenic bleeding. More prospective studies with larger patient samples are necessary for verification of this technique as well as for drawing broader conclusions in order to evaluate the place of percutaneous ablation in the treatment algorithm of haemorrhage.

ADVANCES IN KNOWLEDGE

Percutaneous ablation might have a role in haemostasis in well-selected cases.

Evaluation of the MR and pathology characteristics immediately following percutaneous MR-guided microwave ablation in a rabbit kidney VX2 tumor implantation model

Purpose: This study aimed to evaluate the immediate efficacy of magnetic resonance (MR)-guided microwave ablation (MWA) in rabbit kidneys implanted with VX2 tumors.Materials and methods: MR-guided MWA was performed in eight VX2 tumor-bearing rabbits. MR images after ablation were obtained and analyzed. The differences between the tissue specimens and MR images obtained after ablation were compared.Results: On the three-dimensional volumetric interpolated breath-hold T1-weighted (3D-VIBE-T1WI) sequence, a low signal intensity indicated the primary tumor at the center of the ablation area, which was surrounded by a peripheral high-signal area. The signal for the primary tumor in the fast spin-turbo spin-echo T2-weighted (FS-TSE-T2WI) sequence was lower than before, and the ablation zone showed a low signal that completely covered the primary tumor. There was no significant difference in volume among the low-signal areas of the primary tumor on FS-TSE-T2WI before MWA, the central low-signal area on 3D-VIBE-T1WI after MWA, and the tumor coagulation necrosis area on the tissue specimens (p > 0.05). No significant difference was found in the volume of ablation zones among the tissue specimens, the high-signal area around the lesion on the 3D-VIBE-T1WI sequence, and the low-signal area covering the lesion on the FS-TSE-T2WI sequence (p > 0.05).Conclusion: Magnetic resonance imaging (MRI) is an effective method for immediate efficacy evaluation of rabbit renal VX2 tumors after MWA and can serve as a valuable reference for the clinical assessment of post-ablative renal tumors.

Trends in Percutaneous Thermal Ablation Therapies in the Treatment of T1a Renal Cell Carcinomas Rather than Partial Nephrectomy/Radical Nephrectomy

With the increased incidence of stage T1a renal cell carcinoma (RCC) has come the recognition that these lesions tend to be low grade and slow growing, with low probability of metastasis not necessarily requiring surgery. As alternatives to surgery, both active surveillance and ablation have been advocated for the management of selected patients with stage T1a renal cancers due to slow rate of tumor growth and low metastatic potential based on recent epidemiological studies. Thermal ablation also has consistently reported favorable complication and renal preservation rates compared with surgical approaches. However, most studies are single-center case series and meta-analysis of these series and comparative prospective series with long-term follow-up are lacking. The purpose of this article is to review the principal thermal ablation modalities and oncological outcomes for the treatment of stage T1 RCCs with long-term follow-up.

[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.

Partial nephrectomy versus ablative techniques for small renal masses: a systematic review and network meta-analysis

PURPOSE

To compare partial nephrectomy (PN), radiofrequency ablation (RFA), cryoablation (CRA) and microwave ablation (MWA) regarding oncologic, perioperative and functional outcomes.

MATERIAL AND METHODS

The MEDLINE, EMBASE and COCHRANE libraries were searched for studies comparing PN, RFA, CRA or MWA and reporting on any-cause or cancer-specific mortality, local recurrence, complications or renal function. Network meta-analyses were performed.

RESULTS

Forty-seven studies with 24,077 patients were included. Patients receiving RFA, CRA or MWA were older and had more comorbidities compared with PN. All-cause mortality was higher for CRA and RFA compared with PN (incidence rate ratio IRR = 2.58, IRR = 2.58, p < 0.001, respectively). No significant differences in cancer-specific mortality were evident. Local recurrence was higher for CRA, RFA and MWA compared with PN (IRR = 4.13, IRR = 1.79, IRR = 2.52, p < 0.05 respectively). A decline in renal function was less pronounced after RFA versus PN, CRA and MWA (mean difference in GFR MD = 6.49; MD = 5.82; MD = 10.89, p < 0.05 respectively).

CONCLUSION

Higher overall survival and local control of PN compared with ablative therapies did not translate into significantly better cancer-specific mortality. Most studies carried a high risk of bias by selecting younger and healthier patients for PN, which may drive superior survival and local control. Physicians should be aware of the lack of high-quality evidence and the potential benefits of ablative techniques for certain patients, including a superior complication profile and renal function preservation.

KEY POINTS

• Patients selected for ablation of small renal masses are older and have more comorbidities compared with those undergoing partial nephrectomy. • Partial nephrectomy yields lower all-cause mortality, which is probably biased by patient selection and does not translate into prolonged cancer-free survival. • The decline of renal function is smallest after radiofrequency ablation for small renal masses.

The efficacy and safety of microwave ablation in patients with retroperitoneal metastases

BACKGROUND

Retroperitoneal metastases are common, and most present with symptoms; however, treatments for this condition are limited. This retrospective study verified the efficacy and safety of microwave ablation (MWA) in retroperitoneal metastases patients.

METHODS

Patients with pathologically confirmed malignant carcinoma and imaging showing retroperitoneal metastases were enrolled and underwent MWA. The end-points included objective response rate, time to local progression (TTLP), overall survival, visual analogue scale (VAS) score, dose of morphine pre- and post-ablation and complications.

RESULTS

Twenty-three patients were enrolled. The mean tumour diameter was 3.6 cm. Altogether, 29 tumour sites in 23 patients were ablated during 23 procedures; technical success was achieved in all 23 patients. The objective response and disease control rates were 95.7% and 100.0%, respectively. The mean TTLP and median OS were 22.8 months (95% CI: 16.1-29.6 months) and 10.6 months (95% CI: 7.4-13.8 months), respectively. In 13 patients with symptoms, the VAS values before ablation and 48 h, 1 month, 2 months, 3 months and 6 months after ablation were 5.38, 2.77 (p = 0.015), 2.15 (p = 0.001), 2.17 (p = 0.001), 1.40 (p = 0.000) and 1.71 (p = 0.006), respectively. The corresponding morphine doses were 76.9 mg, 70.7 mg (p = 0.584), 50.7 mg (p = 0.031), 55.0 mg (p = 0.097), 46.0 mg (p = 0.057) and 40.0 mg (p = 0.363), respectively. No ablation-associated mortality was observed. Major complications, minor complications and adverse events were observed in eight (34.8%), five (21.7%) and four (17.4%) patients, respectively.

CONCLUSION

MWA for the treatment of retroperitoneal metastases was effective and the complications were common.

[What can/should be treated in kidney tumors and when]

CLINICAL/METHODICAL ISSUE

In the treatment of localized renal cell carcinoma, the lack of randomization in controlled trials on thermal ablation is a major limitation. The latter leads to significant study bias and it ultimately remains unclear whether the improved overall survival in favor of partial nephrectomy can actually be attributed to the treatment method.

STANDARD RADIOLOGICAL METHODS

For T1a (≤4 cm) renal cell carcinoma without lymph node and distant metastases, excellent technical and clinical results have been described after imaging-guided radiofrequency ablation and cryoablation.

METHODICAL INNOVATIONS

Low major complication rates, preservation of renal function and three-dimensional confirmation of negative ablation margins (A0 ablation) are the advantages of computed tomography (CT)-guided thermal ablation.

PERFORMANCE

According to the results of controlled (non-randomized) trials on T1a renal cell cancer, the cancer-specific survival rates are comparable between ablative and surgical techniques.

ACHIEVEMENTS

It is high time for prospective randomized controlled trials to define the actual value of percutaneous thermal ablation and partial nephrectomy in the treatment of T1a renal cell carcinoma.

PRACTICAL RECOMMENDATIONS

Apart from localized renal cell carcinoma, angiomyolipoma and oncocytoma can be treated by thermal ablation. Transarterial embolization extends the radiological spectrum for the treatment of renal tumors, either as complementary embolization (e. g. before thermal ablation of T1a and T1b renal cell carcinoma), prophylactic embolization (e. g. angiomyolipoma >6 cm), preoperative embolization (e. g. before laparoscopic partial nephrectomy) or palliative embolization (e. g. in patients with symptomatic macrohematuria due to renal cell carcinoma).

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.

[Focal therapy for small renal masses : Observation, ablation or surgery]

BACKGROUND

The rising incidence of renal cell carcinoma, its more frequent early detection (stage T1a) and the increasing prevalence of chronic renal failure with higher morbidity and shorter life expectancy underscore the need for multimodal focal nephron-sparing therapy.

DISCUSSION

During the past decade, the gold standard shifted from radical to partial nephrectomy. Depending on the surgeon's experience, the patient's constitution and the tumor's location, the intervention can be performed laparoscopically with the corresponding advantages of lower invasiveness. A treatment alternative can be advantageous for selected patients with high morbidity and/or an increased risk of complications associated with anesthesia or surgery. Corresponding risk stratification necessitates previous confirmation of the small renal mass (cT1a) by histological examination of biopsy samples. Active surveillance represents a controlled delay in the initiation of treatment.

RESULTS

Percutaneous radiofrequency ablation (RFA) and laparoscopic cryoablation are currently the most common treatment alternatives, although there are limitations particularly for renal tumors located centrally near the hilum. More recent ablation procedures such as high intensity focused ultrasound (HIFU), irreversible electroporation, microwave ablation, percutaneous stereotactic ablative radiotherapy and high-dose brachytherapy have high potential in some cases but are currently regarded as experimental for the treatment of renal cell carcinoma.

Percutaneous microwave ablation of renal cancers under CT guidance: safety and efficacy with a 2-year follow-up

AIM

To evaluate the safety and efficiency of percutaneous microwave ablation (MWA) of renal cell carcinomas (RCC) carried out under computed tomography (CT) guidance.

MATERIALS AND METHODS

A retrospective study was performed on RCC that was either histologically proven or diagnosed at imaging (Bosniak IV cyst) and treated by MWA under general anaesthesia with CT guidance. Indications for percutaneous ablation were based on the American Urological Association recommendations. Twenty-four months post-procedure follow-up was performed.

RESULTS

Sixty-two patients presenting one or more RCC (84 tumours ranging from 10-48 mm in diameter; mean diameter: 25.6 mm) were included. Technical success was achieved for 78 tumours (58 patients). For four patients, the treatment was stopped due to gas dissection failure. At 3 months, six residual tumours were observed (8%). At 6 months, two recurrences and one residual tumour (3.8%) were observed; all were retreated with complete success. At 12 months, local control of the disease was achieved in 94% of cases (100% in cases where treatment was performed). Two cases of distal metastasis were observed after 12 and 24 months. At 24 months, one patient presented with a contralateral tumour. The complication rate was 4.8% including one grade III complication and two grade II complications according to the Clavien-Dindo classification. At 2 years, the cumulative disease-free survival rate and overall survival were 95% and 97%, respectively.

CONCLUSION

MWA ablation under CT guidance to treat RCC is safe and provides a high rate of effectiveness at 24 months.

Microwave ablation of malignant renal tumours: intermediate-term results and usefulness of RENAL and mRENAL scores for predicting outcomes and complications

The aim of this study was to evaluate intermediate-term results after microwave ablation (MWA) of renal tumours and determine the association of RENAL and modified RENAL (mRENAL) scores with oncological outcomes and complications. In May 2008-September 2014, 58 patients affected by early-stage RCC (renal cell carcinoma; T1a or T1b) were judged unsuitable for surgery and treated with percutaneous MWA. Follow-up was performed with contrast-enhanced computed tomography at 1, 3, 6, 12 and 24 months after the procedure. Technical success (TS), primary technical effectiveness (PTE), secondary technical effectiveness (STE), the local tumour progression rate (LTPR), the cancer-specific survival rate (CSSR), disease-free survival (DFS), overall survival (OS) and safety were recorded. All lesions were evaluated using RENAL and mRENAL scores, and complications were assessed with RENAL scores. The TS rate was 100%, PTE was 93%, STE was 100%, LTPR was 15.7% at 1 year, CSSR was 96.5%, DFS was 87.9% at 5 years, and OS was 80.6%. Mean follow-up was 25.7 months (range 3-72). The mean ± standard deviation (SD) RENAL and mRENAL scores of all treated tumours were 6.7 ± 2.05 (range 4-11) and 7 ± 2.3 (range 4-12), respectively. Major complications occurred in two (2/58) and minor complications in three patients (3/58). Overall complications correlated significantly with RENAL scores; in particular, E and L represent negative predictors for safety and effectiveness. MWA is a valuable alternative for treating RCCs. The correlation with outcomes and complications of RENAL and mRENAL scores could help to customise MWA indications in RCC patients.

Radiofrequency versus microwave ablation for treatment of the lung tumours: LUMIRA (lung microwave radiofrequency) randomized trial

The LUMIRA trial evaluated the effectiveness of radiofrequency (RFA) and microwave ablation (MWA) in lung tumours ablation and defining more precisely their fields of application. It is a controlled prospective multi-centre random trial with 1:1 randomization. Fifty-two patients in stage IV disease (15 females and 37 males, mean age 69 y.o., range 40-87) were included. We randomized the patients in two different subgroups: MWA group and RFA group. For each group, we evaluated the technical and clinical success, the overall survival and complication rate. Inter-group difference was compared using Chi-square test or Fisher's exact test for categorical variables and one-way ANOVA test for continuous variables. For RFA group, there was a significant reduction in tumour size only between 6 and 12 months (p value = 0.0014). For MWA group, there was a significant reduction in tumour size between 6 and 12 months (p value = 0.0003) and between pre-therapy and 12 months (p value = 0.0215). There were not significant differences between the two groups in terms of survival time (p value = 0.883), while the pain level in MWA group was significantly less than in RFA group (1.79 < 3.25, p value = 0.0043). In conclusion, our trial confirms RFA and MWA are both excellent choices in terms of efficacy and safety in lung tumour treatments. However, when compared to RFA therapy, MWA produced a less intraprocedural pain and a significant reduction in tumour mass.

Image-guided percutaneous microwave ablation of small renal tumours: short- and mid-term outcomes

BACKGROUND

The purpose is to assess the short- and mid-term outcomes of microwave ablation (MWA) of small renal tumours in selected patients.

METHODS

From August 2012 to February 2015, 29 renal tumours in 23 patients (17 male, 6 female, mean age 75 years) were treated by percutaneous MWA under imaging guidance. The tumours were 1-4.7 cm in diameter (mean size, 2.7 cm). Therapeutic effects were assessed at follow-up with magnetic resonance imaging (MRI). All patients were followed up for 2-25 months (mean, 12.2 months) to observe the therapeutic effects and complications. Changes in renal function at day 1 after treatment were statistically analyzed using the Student paired t-test or the paired Wilcoxon test.

RESULTS

Technical success was achieved in all cases. One severe bleeding complication post-procedure occurred leading to death. No other unexpected side effects were observed after the MWA procedures. Clinical effectiveness was 100%. None of the patients showed recurrence on MRI imaging follow-up. No significant changes in renal function were noted after treatment (P=0.57).

CONCLUSIONS

Our preliminary study demonstrates that the use of MWA for the treatment of small renal tumours can be applied as safely and efficiently as other ablative techniques in selected patients not eligible for surgery.

Thermal Ablation of Renal Tumors: Indications, Techniques and Results

BACKGROUND

About 15,000 persons receive the diagnosis of kidney cancer in Germany every year. Surgical resection is the standard treatment for locally confined tumors, but minimally invasive thermoablative techniques are increasingly being used as well.

METHODS

This article is based on publications retrieved by a selective literature search in PubMed regarding the thermoablative techniques now used in clinical practice, with particular attention to radiofrequency ablation (RFA) and cryoablation (CA).

RESULTS

RFA and CA are suitable for patients who cannot undergo surgery because of comorbid illnesses or who have contralateral recurrences or a hereditary precancerous condition. The primary technical success rate of these procedures ranges from 88% to 100%. More than 95% of tumors under 3 cm in diameter can be completely ablated. Reported complication rates range from 1% to 7%. New data on long-term outcomes reveal metastasis-free survival rates of 88% to 99% five years after ablation. A major advantage of these procedures is that thermoablation does not impair renal function to any relevant extent and is thus a good option for patients with limited renal function or a single kidney.

CONCLUSION

The thermoablative techniques are an important addition to the armamentarium of effective treatments for locally confined renal tumors. The guidelines of the American and European urological societies now list thermoablation with RFA or CA as an option for the treatment of small renal tumors with curative intent. Thermoablation of renal tumors has not yet been studied in randomized controlled trials; these will be needed so that the efficacy of tumor control, survival rates, complication rates, and quality of life after treatment can be reliably evaluated to provide definitive confirmation of the value of interstitial techniques.