Percutaneous Microwave Ablation of Category T1a Renal Cell Carcinoma: Intermediate Results on Safety, Technical Feasibility, and Clinical Outcomes of 119 Tumors

Tissue Ablation: Applications and Perspectives

Tissue ablation techniques have emerged as a critical component of modern medical practice and biomedical research, offering versatile solutions for treating various diseases and disorders. Percutaneous ablation is minimally invasive and offers numerous advantages over traditional surgery, such as shorter recovery times, reduced hospital stays, and decreased healthcare costs. Intra-procedural imaging during ablation also allows precise visualization of the treated tissue while minimizing injury to the surrounding normal tissues, reducing the risk of complications. Here, the mechanisms of tissue ablation and innovative energy delivery systems are explored, highlighting recent advancements that have reshaped the landscape of clinical practice. Current clinical challenges related to tissue ablation are also discussed, underlining unmet clinical needs for more advanced material-based approaches to improve the delivery of energy and pharmacology-based therapeutics.

Percutaneous Microwave Ablation versus Cryoablation for Small Renal Masses (≤4 cm): 12-Year Experience at a Single Center

PURPOSE

To determine whether microwave ablation (MWA) has equivalent outcomes to those of cryoablation (CA) in terms of technical success, adverse events, local tumor recurrence, and survival in adult patients with solid enhancing renal masses ≤4 cm.

MATERIALS AND METHODS

A retrospective review was performed of 279 small renal masses (≤4 cm) in 257 patients (median age, 71 years; range, 40-92 years) treated with either CA (n = 191) or MWA (n = 88) between January 2008 and December 2020 at a single high-volume institution. Evaluations of adverse events, treatment effectiveness, and therapeutic outcomes were conducted for both MWA and CA. Disease-free, metastatic-free, and cancer-specific survival rates were tabulated. The estimated glomerular filtration rate was employed to examine treatment-related alterations in renal function.

RESULTS

No difference in patient age (P = .99) or sex (P = .06) was observed between the MWA and CA groups. Cryoablated lesions were larger (P < .01) and of greater complexity (P = .03). The technical success rate for MWA was 100%, whereas 1 of 191 cryoablated lesions required retreatment for residual tumor. There was no impact on renal function after CA (P = .76) or MWA (P = .49). Secondary analysis using propensity score matching demonstrated no significant differences in local recurrence rates (P = .39), adverse event rates (P = .20), cancer-free survival (P = .76), or overall survival (P = .19) when comparing matched cohorts of patients who underwent MWA and CA.

CONCLUSIONS

High technical success and local disease control were achieved for both MWA and CA. Cancer-specific survival was equivalent. Higher adverse event rates after CA may reflect the tendency to treat larger, more complex lesions with CA.

Percutaneous ablation of renal tumors: Long-term outcomes

OBJECTIVE

To evaluate the long-term outcomes of renal tumor ablation, analyzing efficacy, long-term survival, and factors associated with complications and therapeutic success.

MATERIAL AND METHODS

We retrospectively reviewed 305 ablations (generally done with expandable electrodes) of 273 renal tumors between May 2005 and April 2019. We analyzed survival, primary and secondary efficacy, and complications according to various patient factors and tumor characteristics.

RESULTS

Mean blood creatinine was 1.14 mg/dL before treatment and 1.30 mg/dL after treatment (p < 0.0001). Complications were observed in 13.25% of the ablations, including major complications in in 4.97%. Complications were associated with age (p = 0.013) and tumor diameter (p < 0.0001). Primary efficacy was 96.28%. Incomplete ablation was more common in lesions measuring > 4 cm in diameter (p = 0.002). Secondary efficacy was 95.28%. The only factor associated with the risk of recurrence was the size of the tumor (p = 0.02). Overall survival was 95.26% at 1 year, 77.01% at 5 years, and 51.78% at 10 years, with no differences between patients with malignant and benign lesions. Mortality was higher in patients with creatinine >1 (p = 0.05) or ASA > 2 (p = 0.0001).

CONCLUSIONS

Percutaneous ablation is extremely efficacious for renal tumors; it improves the prognosis of renal carcinoma to the point where it does not differ from that of benign lesions. Complications are rare. Like survival, complications are associated with age and overall health status.

Computed tomography-guided percutaneous microwave ablation for renal cell carcinoma: evaluating the performance of nephrometry scores

OBJECTIVES

The purpose of the current study is to evaluate the performance of RENAL and mRENAL scores, in the prediction of oncological outcomes in patients treated with microwave ablation (MWA) for (T1) renal cell carcinomas (RCC).

METHODS

Institutional database retrospective research identified 76 patients with a biopsy-proven solitary T1a (84%) or T1b (16%) RCC; all patients underwent CT-guided MWA ablation. Tumor complexity was reviewed by calculating RENAL and mRENAL scores.

RESULTS

The majority of the lesions were exophytic (82.9%), with > 7 mm nearness to the collecting system (53.9%), located posteriorly (73.6%), and lower to polar lines (61.8%). Mean RENAL and mRENAL scores were 5.7 (SD = 1.9) and 6.1 (SD = 2.1) respectively. Progression rates were significantly higher with greater tumor size (> 4 cm), with < 4 mm nearness to the collecting system, for tumors crossing a polar line and with the anterior location. None of the above was associated with complications. RENAL and mRENAL scores were significantly higher in patients with incomplete ablation. The ROC analysis showed the significant prognostic ability of both RENAL and mRENAL scores for progression. In both scores, the optimal cut-off point was 6.5. Univariate Cox regression analysis for progression showed a hazard ratio of 7.73 for the RENAL score and 7.48 for the mRENAL score.

CONCLUSION

The results of the present study show that the risk of progression was higher in patients with RENAL and mRENAL score of > 6.5, in T1b tumors, close to the collective system (< 4 mm), crossing polar lines and anterior location.

CLINICAL RELEVANCE STATEMENT

CT-guided percutaneous MWA is a safe and effective technique for the treatment of T1a renal cell carcinomas. Different morphometric parameters of RCC tumors including RENAL and mRENAL score > 6.5, size, proximity to the collecting system, and crossing of polar lines impact the efficacy of MWA and progression survival rates.

KEY POINTS

• The risk of progression is higher in patients with RENAL and mRENAL score > 6.5, in T1b tumors, close to the collective system (< 4 mm), crossing polar lines and anterior location. • The significant prognostic ability of the mRENAL score for progression was higher than the respective of the RENAL score. • Complications were not associated with any of the above factors.

Recent Advances in the Management of Localized and Locally Advanced Renal Cell Carcinoma: A Narrative Review

Purpose

To review the current status of surgical and procedural treatments for renal cell carcinoma (RCC), focusing on oncological and functional outcomes, and the use of techniques for advanced disease over the last 10 years.

Findings

Partial nephrectomy (PN) has become the reference standard for most T1 and T2 masses. In cT2 RCC, PN exhibits oncological equivalence and improved functional outcomes compared to radical nephrectomy (RN). Additionally, emerging data suggest that PN may be used to treat cT3a RCC. The robot-assisted platform is increasingly used to treat locally advanced RCC. Studies suggest safety and feasibility of robotic RN and robotic inferior vena cava tumor thrombectomy. Additionally, single-port robot-assisted laparoscopic approaches are comparable to multiport approaches in select patients. Long-term data show that cryoablation, radiofrequency ablation, and microwave ablation are equipotent in management of small renal masses. Emerging data suggest that microwave may effectively treat cT1b masses.

The Role of Focal Therapy and Active Surveillance for Small Renal Mass Therapy

Small and low-grade renal cell carcinomas have little potential for metastasis and disease-related mortality. As a consequence, the main problem remains the use of appropriately tailored treatment for each individual patient. Surgery still remains the gold standard, but many clinicians are questioning this approach and present the advantages of focal therapy. The choice of treatment regimen remains a matter of debate. This article summarizes the current treatment options in the management of small renal masses.

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).

Computed Tomography-Guided Percutaneous Microwave Ablation for Renal Cell Carcinoma: Impact of Tumor Size on the Progression Survival Rates

The aim of the present study was to evaluate the safety and efficacy of computed tomography (CT)-guided percutaneous microwave ablation (MWA) of renal cell carcinoma (RCC) along with identifying prognostic factors affecting the progression survival rate. Institutional database retrospective research identified 69 patients with a biopsy proven solitary T1a (82.6%) or TIb (17.4%) RCC who have underwent percutaneous CT-guided MWA. Kaplan–Meier survival estimates for events were graphed and Cox regression analysis was conducted. Mean patient age was 70.4 ± 11.5 years. Mean size of the lesions was 3 ± 1.3 cm. Mean follow up time was 35.6 months (SD = 21.1). The mean progression free survival time from last ablation was 84.2 months. For T1a tumors, the cumulative progression free survival rate for 1, 6, 12 and 36 months were 100% (SE = 0%), 91.2% (SE = 3.7%), 91.2% (SE = 3.7%) and 87.5% (SE = 4.4%); the recurrence free survival rate for T1a RCC was 94.9%. For T1b tumors, the cumulative progression free survival rate for 1, 6, 12 and 36 months were 100% (SE = 0%), 63.6% (SE = 14.5%), 63.6% (SE = 14.5%) and 63.6% (SE = 14.5%). Grade 1 complications were recorded in 5 (7.2%) patients. Significantly greater hazard for progression was found in cases with a tumor size > 4 cm (HR = 9.09, p = 0.048). No statistically important difference regarding tumor progression was recorded between T1a tumors with a diameter ≤3 cm and >3 cm. In summary, the results of the present study show that CT guided percutaneous MWA is an effective technique for treatment of T1a renal cell carcinomas, irrespective of tumor size. T1b tumors were associated with higher progression rates.

[Percutaneous local ablation of small renal cell cancer]

Renal cell carcinoma (RCC) is a cancer that mainly occurs in elderly patients. Percutaneous image-guided ablation of small RCC (< 4 cm) is a validated therapeutic option, especially as many patients are no candidates for surgery due to comorbidities. This article presents and discusses established local ablative techniques such as radiofrequency (RFA), microwave (MWA) and cryoablation for the treatment of small RCC based on current literature and in the context of the latest guidelines.

MR-Guided Microwave Ablation in T1 Renal Cell Carcinoma: Initial Results in Clinical Routine

Objective

Percutaneous tumor ablation is usually performed using computed tomography (CT) or ultrasound (US) guidance, although reliable visualization of the target tumor could be challenging. Magnetic resonance- (MR-) guided ablation provides more reliable visualization of the target tumors and allows multiplanar imaging of the treatment process, making it the modality of choice, in particular if lesions are small.

Methods

From March 2016 to January 2018, 32 patients scheduled for percutaneous treatment of T1 RCC underwent MR-guided MWA. Complications were classified according to the Clavien grade. Kaplan–Meier survival estimates were calculated to evaluate progression-free survival (PFS).

Results

Technical success was achieved in all lesions. The mean energy and procedure duration were 61.6 ± 8.7 kJ and 118.2 ± 26.7 min, respectively. The glomerular filtration rate (GFR) dropped rapidly after 1 month of treatment and slowly recovered within three months (P < 0.05). Postoperative pain and fever were the most common adverse events after treatment. Perirenal hematoma, thermal injury of the psoas muscle, and abdominal distension were common complications after MWA, and the incidence rates were 9.4% (3/32), 6.3% (2/32), and 6.3% (2/32), respectively. According to the Clavien grade classification, serious complications include hydrothorax, bowel injury, and renal failure, all of which have a probability of 3.1%. Of note, the three serious complications occurred in one patient. The 1-, 2-, and 3-year PFS rates were 96.9%, 93.8%, and 83.9%, respectively. The mean PFS rates were 33.972 months (95% CI: 33.045, 35.900).

Conclusion

Microwave ablation is feasible under MR guidance and provides effective treatment of RCC in one session.

Thermal Ablation of Renal Cell Carcinoma in Patients With Morbid Obesity: Assessment of Technique, Safety, and Oncologic Outcomes

BACKGROUND. Obesity is a worldwide problem that impacts patient health as well as the morbidity associated with surgical procedures. Thus, patients with morbid obesity may not be suitable candidates for curative surgery. For this patient population, thermal ablation may be an effective alternative to nephrectomy. OBJECTIVE. The purpose of this study was to determine the feasibility, oncologic outcomes, and survival of patients with morbid obesity and renal cell carcinoma treated with thermal ablation. MATERIALS AND METHODS. A retrospective analysis was performed of 107 patients treated with CT-guided renal ablation for clinical T1 renal cell carcinoma between February 2005 and December 2017. Patients were stratified into two cohorts on body mass index of ≥ 40 kg/m² (morbidly obese) and body mass index (weight in kilograms divided by the square of height in meters) of ≥ 40 (morbidly obese) and 18.5-24.9 (normal weight). Anesthetic and radiation dosages, procedure time, residual disease, and local recurrence, and adverse events were analyzed between the two groups. Kaplan-Meier statistics were used to evaluate cancer-related outcomes for each group. RESULTS. Thirty-four patients were morbidly obese, and 73 patients had normal weight. Morbid obesity was associated with longer procedural duration (p = .001), sedative doses (p = .002) and radiation exposure (p = .001) than normal weight. Hematomas were more prevalent in patients with morbid obesity than in those of normal weight (p = .01), but treatment efficacy and local recurrences were comparable with those for normal-weight individuals (p = .81 and p = .12, respectively). Cancer-related outcomes were equivalent between the two groups based on 5 years of imaging observation data. CONCLUSION. CT-guided thermal ablation remains technically feasible, well-tolerated, and effective in patients with morbid obesity and renal cell carcinoma, with the caveat of increased risk of perinephric hematoma, anesthesia dose, and radiation exposure. CLINICAL IMPACT. CT-guided thermal ablation can be considered a safe and effective treatment for renal cell carcinoma in patients with morbid obesity.