CT-guided Bipolar and Multipolar Radiofrequency Ablation (RF Ablation) of Renal Cell Carcinoma: Specific Technical Aspects and Clinical Results

Thermal immuno-nanomedicine in cancer

Immunotherapy has revolutionized the treatment of patients with cancer. However, promoting antitumour immunity in patients with tumours that are resistant to these therapies remains a challenge. Thermal therapies provide a promising immune-adjuvant strategy for use with immunotherapy, mostly owing to the capacity to reprogramme the tumour microenvironment through induction of immunogenic cell death, which also promotes the recruitment of endogenous immune cells. Thus, thermal immunotherapeutic strategies for various cancers are an area of considerable research interest. In this Review, we describe the role of the various thermal therapies and provide an update on attempts to combine these with immunotherapies in clinical trials. We also provide an overview of the preclinical development of various thermal immuno-nanomedicines, which are capable of combining thermal therapies with various immunotherapy strategies in a single therapeutic platform. Finally, we discuss the challenges associated with the clinical translation of thermal immuno-nanomedicines and emphasize the importance of multidisciplinary and inter-professional collaboration to facilitate the optimal translation of this technology from bench to bedside.

Local anesthesia for percutaneous US/CT-guided bipolar radiofrequency ablation of small renal masses: A safe and feasible alternative

PURPOSE

This study is to evaluate the safety and feasibility of local anesthesia (LA) for percutaneous ultrasound/computed tomography (US/CT)-guided bipolar radiofrequency ablation (RFA) for small renal masses (SRMs) by comparing the LA with general anesthesia.

MATERIALS AND METHODS

A retrospective review was carried out between January 2018 to June 2020, 102 patients with SRMs were treated with US/CT-guided bipolar RFA. General anesthesia (GA) was performed in 42 and LA was performed in 60 patients. Demographics, tumor characteristics, peri-procedural data, pathologic and follow-up outcomes were analyzed. The factors associated with pain were also identified.

RESULTS

There was no significant difference in demographics and tumor characteristics between the LA and GA group. A statistically significant difference was observed in terms of procedural time (P = 0.010) and hospital stays (P < 0.001). The maximum perceived pain in LA group comprised 60.0% (36 of 60) mild, 40.0% (24 of 60) moderate. The anxiety in LA group comprised 65.0% (39 of 60) mild, 33.3% (20 of 60) moderate, 1.7% (1 of 60) severe. On multivariate analysis, tumor diameter was a significant predictor for pain in RFA procedure (OR 1.560, 95% CI 1.233-1.974, P < 0.001). All patients were followed up for a median (range) of 12 (2-24) months. Local recurrence occurred in 8.3% (5 of 60) of the LA group and in 7.1% (3 of 42) in GA group (P = 1.000).

CONCLUSION

Percutaneous bipolar RFA of SRMs using CT and ultrasound guidance under LA can be an effective and tolerable method for patients who are unfit for surgery and provide satisfactory oncologic control.

Phase Contrast Imaging Based Microbubble Monitoring of Radiofrequency Ablation: An ex vivo Study

Background

To explore the potential of synchrotron radiation (SR) phase contrast imaging (PCI) for real-time microbubble formation monitoring during radiofrequency ablation (RFA).

Methods

RFA was performed on ex vivo porcine muscle tissue using unipolar and multi-tined expandable electrodes. Images of microbubble formation in the samples were captured by both SR PCI and absorption contrast imaging. The synchronous ablation temperature was recorded. Each RFA electrode type group contained 6 samples. Ablation size was assessed by histologic examination.

Results

Microbubble formation during RFA could be visualized by SR PCI. The diameter of the microbubbles revealed on the image ranged from tens of microns to several millimeters, and these microbubbles first appeared at the edge of the RFA electrode when the target region temperature reached approximately 60°C and rapidly extended outwards. The average microbubble range measured on PCI was 17.66 ± 0.74 mm. The average range of coagulation necrosis measured by histological examination was 17.22 ± 0.38 mm. There was no significant difference between them (P > 0.05). The range of microbubbles corresponded to the ablation zone.

Conclusion

PCI enabled real-time high-resolution visualization of microbubble formation during RFA, indicating a potential for its use in ablation monitoring.

Renal Cell Carcinoma: Alternative Nephron-Sparing Treatment Options for Small Renal Masses, a Systematic Review

BACKGROUND

The standard treatment of T1 renal cell carcinoma (RCC) is (partial) nephrectomy. For patients where surgery is not the treatment of choice, for example in the elderly, in case of severe comorbidity, inoperability, or refusal of surgery, alternative treatment options are available. These treatment options include active surveillance (AS), radiofrequency ablation (RFA), cryoablation (CA), microwave ablation (MWA), or stereotactic body radiotherapy (SBRT). In the present overview, the efficacy, safety, and outcome of these different options are summarized, particularly focusing on recent developments.

MATERIALS AND METHODS

Databases of MEDLINE (through PubMed), EMBASE, and the Cochrane Library were systematically searched according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) criteria. The search was performed in December 2016, and included a search period from 2010 to 2016. The terms and synonyms used were renal cell carcinoma, active surveillance, radiofrequency ablation, microwave ablation, cryoablation and stereotactic body radiotherapy.

RESULTS

The database search identified 2806 records, in total 73 articles were included to assess the rationale and clinical evidence of alternative treatment modalities for small renal masses. The methodological quality of the included articles varied between level 2b and level 4.

CONCLUSION

Alternative treatment modalities, such as AS, RFA, CA, MWA, and SBRT, are treatment options especially for those patients who are unfit to undergo an invasive treatment. There are no randomized controlled trials available comparing surgery and less invasive modalities, leading to a low quality on the reported articles. A case-controlled registry might be an alternative to compare outcomes of noninvasive treatment modalities in the future.

Laparoscopic Radiofrequency Ablation versus Partial Nephrectomy for cT1a Renal Tumors: Long-Term Outcome of 179 Patients

OBJECTIVES

To compare the long-term functional and oncological results between laparoscopic radiofrequency ablation (LRFA) and laparoscopic partial nephrectomy (LPN) in selected clinical T1a (cT1a) renal tumor patients.

METHODS

We retrospectively analyzed the medical records of patients with cT1a renal tumors who had LRFA or LPN at our institution between February 2006 and February 2015. Student's t test was used to compare the perioperative data between the two groups. Survival analyses were calculated using the Kaplan-Meier method.

RESULTS

A total of 179 patients were included in the study. Patients in the LRFA cohort were significantly older and had higher American Society of Anesthesiologists sore than in the LPN cohort. The LRFA group had a significantly lower mean blood loss than the LPN group (p = 0.03). The percent decrease of GFR in the LRFA group was significantly lower than in the LPN group (p = 0.021). The 5-year overall, cancer-specific and disease-free survival were 93.3 vs. 94.6%, 98.0 vs. 98.5% and 97.1 vs. 97.3%, for LRFA and LPN, respectively (all p value >0.05).

CONCLUSIONS

The excellent perioperative results, long-term functional and oncological outcomes of LRFA confirm that this technique is safe, nephron sparing and oncologically effective for the treatment of cT1a renal tumors.

[Percutaneous radiofrequency ablation of renal tumors: update 2015]

BACKGROUND

Stage I renal cell carcinoma is a malignancy with a relatively good prognosis. The incidence of all renal cell carcinomas is approximately 9/100,000 persons. There are nearly 15,000 newly diagnosed patients every year (men twice as often as women).

TREND

In the last decade, a trend away from radical open resection towards nephron-sparing approaches has been observed. Currently, partial nephrectomy is the surgical gold standard for the treatment of small renal tumors. However, excellent clinical results are obtained using percutaneous radiofrequency ablation (RFA): low complication rates and preservation of the renal function.

RESULTS

Primary and secondary technical success rates are 69-100% and 90-100%, respectively. In large series, major complication rates of RFA of 0-14% are reported. A relevant deterioration of renal function after RFA is very rare. The 5-year local recurrence-free survival rates, metastasis-free survival rates, cancer-specific survival rates, and overall survival rates are 88-93, 95-100, 98-100, and 58.3-85%, respectively. In this context, the lack of appropriate long-term data is often cited as a limitation.

CONCLUSION

Different meta-analyses come to the conclusion that in case of adequate tumor and patient selection RFA shows oncologic results comparable with surgical resection. Accepted indications for RFA are T1 renal tumors in patients with advanced age, significant comorbidities, reduced renal function, single kidney, and/or no wish for operation. Predictors for the success include tumor size and location as well as operator experience. To define the real efficacy of RFA in the treatment of renal tumors, randomized controlled clinical long-term studies are indicated.

Sphere-enhanced microwave ablation (sMWA) versus bland microwave ablation (bMWA): technical parameters, specific CT 3D rendering and histopathology

PURPOSE

This study was designed to compare technical parameters during ablation as well as CT 3D rendering and histopathology of the ablation zone between sphere-enhanced microwave ablation (sMWA) and bland microwave ablation (bMWA).

METHODS

In six sheep-livers, 18 microwave ablations were performed with identical system presets (power output: 80 W, ablation time: 120 s). In three sheep, transarterial embolisation (TAE) was performed immediately before microwave ablation using spheres (diameter: 40 ± 10 μm) (sMWA). In the other three sheep, microwave ablation was performed without spheres embolisation (bMWA). Contrast-enhanced CT, sacrifice, and liver harvest followed immediately after microwave ablation. Study goals included technical parameters during ablation (resulting power output, ablation time), geometry of the ablation zone applying specific CT 3D rendering with a software prototype (short axis of the ablation zone, volume of the largest aligned ablation sphere within the ablation zone), and histopathology (hematoxylin-eosin, Masson Goldner and TUNEL).

RESULTS

Resulting power output/ablation times were 78.7 ± 1.0 W/120 ± 0.0 s for bMWA and 78.4 ± 1.0 W/120 ± 0.0 s for sMWA (n.s., respectively). Short axis/volume were 23.7 ± 3.7 mm/7.0 ± 2.4 cm(3) for bMWA and 29.1 ± 3.4 mm/11.5 ± 3.9 cm(3) for sMWA (P < 0.01, respectively). Histopathology confirmed the signs of coagulation necrosis as well as early and irreversible cell death for bMWA and sMWA. For sMWA, spheres were detected within, at the rim, and outside of the ablation zone without conspicuous features.

CONCLUSIONS

Specific CT 3D rendering identifies a larger ablation zone for sMWA compared with bMWA. The histopathological signs and the detectable amount of cell death are comparable for both groups. When comparing sMWA with bMWA, TAE has no effect on the technical parameters during ablation.

Optimisation of the coagulation zone for thermal ablation procedures: a theoretical approach with considerations for practical use

PURPOSE

This paper outlines a theoretical approach for optimisation of the coagulation zone for thermal ablation procedures and considerations for its practical application.

METHODS

The theoretical approach is outlined in the Cartesian coordinate system. Considerations for practical application are implemented. The optimised coagulation zone is defined as the bare coverage of tumour mass plus a safety margin. The eccentricity of coagulation centre (ECC) is defined as the distance between the coagulation centre and the tumour centre. The direction of the applicator shaft is determined based on the x-axis direction. The tumour centre and coagulation centre are defined within the x/y-plane. The distance between coagulation margin (applicator tip) and tumour margin is called parallel offset (PAO).

RESULTS

For spherical coagulation shapes, a linear relationship exists between optimised coagulation diameter and ECC. An exponential relationship exists between optimised coagulation volume and ECC. A complex relationship was found between PAO and determinants of ECC, which are ex and ey. PAO is an extremely important parameter, which allows for determination of the optimal applicator tip position in relation to the tumour margin. It can be calculated in such a manner that the optimised coagulation zone is minimised by neutralising dislocation of the coagulation centre in applicator shaft direction. The latter can be realised by withdrawing or further inserting the applicator shaft.

CONCLUSIONS

The presented concept can be used to optimise the extent of the coagulation zone for thermal ablation procedures after positioning of the applicator. Its inherent advantage is the simple adjustment of the applicator shaft, which obviates the need for a repuncture.