Microwave ablation of cT1a renal cell carcinoma: oncologic and functional outcomes at a single center

Percutaneous Microwave Ablation of Small (<4 cm) Renal Masses Performed under Moderate Sedation

PURPOSE

To determine the technical success, adverse events, local tumor recurrence, and survival in adult patients undergoing microwave ablation (MWA) of small renal masses performed exclusively under moderate sedation.

MATERIALS AND METHODS

A single-institution, retrospective review from 2016 to 2023 of percutaneous, computed tomography-guided MWA for small renal masses (<4 cm) was performed. After addressing exclusion criteria, 66 patients undergoing 72 ablations were included. Patient demographics, comorbidities, tumor characteristics, procedural details, and clinical outcomes were evaluated. Kaplan-Meier analysis of progression-free survival (PFS), cancer-specific survival (CSS), and overall survival (OS) was performed. Kidney function before and after ablation was compared using the nonparametric Mann-Whitney U test.

RESULTS

Seventy-two small renal masses with a mean size of 2.2 cm (SD ± 0.7) underwent MWA with a 2.45-GHz gas-cooled MWA system at 65 W for 5-15 minutes (mean, 39.1 kJ) performed under moderate sedation. Demographics included a mean age of 68.4 years (SD ± 8.3) (n = 62 men) and Charlson Comorbidity Index score of 6.2 (SD ± 2.1). Median sedation doses were 150 mcg (interquartile range [IQR], 100-175 mcg) of fentanyl and 2.5 mg (IQR, 2-3.5 mg) of midazolam. Technical success was 100%, and all patients were discharged the same day. Median follow-up duration was 3.1 years. PFS and OS were 88.1% and 91.9% at 3 years, respectively. CSS was 100%. There were 2 mild adverse events (2.8%) and 3 recurrences (4.2%). Only 9.7% (n = 5) of patients required postprocedural analgesia; no patients required postdischarge analgesic prescriptions.

CONCLUSIONS

MWA of small renal masses under moderate sedation alone demonstrates excellent patient safety profile, tolerability, and effectiveness, allowing operational efficiency, including short procedure times and same-day discharge.

Microwave vs radiofrequency ablation for small renal masses: perioperative and oncological outcomes

OBJECTIVE

To conduct a comprehensive comparison of microwave ablation (MWA) vs radiofrequency ablation (RFA) outcomes in the treatment of small renal masses (SRMs), specifically: TRIFECTA ([i] complete ablation, [ii] absence of Clavien-Dindo Grade ≥III complications, and [iii] absence of ≥30% decrease in estimated glomerular filtration rate) achievement, operative time (OT), and local recurrence rate (LRR).

PATIENTS AND METHODS

We retrospectively analysed 531 patients with SRMs (clinical T1a-b) treated with MWA or RFA at a single centre (2008-2022). First, multivariable logistic regression models were used for testing TRIFECTA achievement. Second, multivariable Poisson regression models were used to evaluate variables associated with longer OT. Finally, Kaplan-Meier plots depicted LRR over time. All analyses were repeated after 1:1 propensity score matching (PSM).

RESULTS

Of 531 patients with SRMs, 373/531 (70.2%) underwent MWA and 158/531 (29.8%) RFA. MWA demonstrated superior TRIFECTA achievement (314/373 [84.2%]) compared to RFA (114/158 [72.2%], P = 0.001). These differences were driven by higher rates of complete ablation in MWA- vs RFA-treated patients (348/373 [93.3%] vs 137/158 [86.7%], P < 0.001). In multivariable logistic regression models, MWA was associated with higher TRIFECTA achievement, compared to RFA, before (odds ratio [OR] 1.92, P = 0.008) and after PSM (OR 1.99, P = 0.023). Finally, the median OT was shorter for MWA vs RFA (105 vs 115 min; P = 0.002). At Poisson regression analyses, MWA predicted shorter OT before (incidence rate ratio [IRR] 0.86, P < 0.001) and after PSM (IRR 0.85, P < 0.001). Local recurrence occurred in 17/373 (4.6%) MWA-treated patients and 21/158 (13.3%) RFA-treated patients (P = 0.29) after a median (interquartile range) follow-up of 24 (8-46) months. There were no differences in the LRR in Kaplan-Meier plots before (P = 0.29) and after PSM (P = 0.42).

CONCLUSION

Microwave ablation provides higher TRIFECTA achievement, and shorter OT than RFA. No significant differences were found regarding the LRR.

The evolving management of small renal masses

Small renal masses (SRMs) are a heterogeneous group of tumours with varying metastatic potential. The increasing use and improving quality of abdominal imaging have led to increasingly early diagnosis of incidental SRMs that are asymptomatic and organ confined. Despite improvements in imaging and the growing use of renal mass biopsy, diagnosis of malignancy before treatment remains challenging. Management of SRMs has shifted away from radical nephrectomy, with active surveillance and nephron-sparing surgery taking over as the primary modalities of treatment. The optimal treatment strategy for SRMs continues to evolve as factors affecting short-term and long-term outcomes in this patient cohort are elucidated through studies from prospective data registries. Evidence from rapidly evolving research in biomarkers, imaging modalities, and machine learning shows promise in improving understanding of the biology and management of this patient cohort.

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.

Limited ability of the renal ablation-specific (MC)2 risk scoring system to predict major adverse events from percutaneous renal microwave ablation

PURPOSE

To access if the (MC)2 scoring system can identify patients at risk for major adverse events following percutaneous microwave ablation of renal tumors.

METHODS

Retrospective review of all adult patients who underwent percutaneous renal microwave ablation at two centers. Patient demographics, medical histories, laboratory work, technical details of the procedure, tumor characteristics, and clinical outcomes were collected. The (MC)2 score was calculated for each patient. Patients were assigned to low-risk (<5), moderate-risk (5-8) and high-risk (>8) groups. Adverse events were graded according to the criteria from the Society of Interventional Radiology guidelines.

RESULTS

A total of 116 patients (mean age = 67.8 [95%CI 65.5-69.9], 66 men) were included. 10 (8.6%) and 22 (19.0%) experienced major or minor adverse events, respectively. The mean (MC)2 score for patients with major adverse events (4.6 [95%CI 3.3-5.8]) was not higher than those with either minor adverse events (4.1 [95%CI 3.4-4.8], p = 0.49) or no adverse events (3.7 [95%CI 3.4-4.1], p = 0.25). However, mean tumor size was greater in those with major adverse events (3.1 cm [95%CI 2.0-4.1]) than minor adverse events (2.0 cm [95%CI 1.8-2.3], p = 0.01). Patients with central tumors were also more likely to experience major adverse events compared to those without central tumors (p = 0.02). The area under the receiver operator curve to predict major adverse events was 0.61 (p = 0.15), indicating a poor ability of the (MC)2 score to predict major adverse events.

CONCLUSION

The (MC)2 risk scoring system does not accurately identify patients at risk for major adverse events from percutaneous microwave ablation of renal tumors. The mean tumor size and central tumor location may serve as a better indicator for risk assessment of major adverse events.

Percutaneous Microwave Ablation is Comparable to Cryoablation for the Treatment of T1a Renal Masses: Results From a Cross-Sectional Study

INTRODUCTION

Percutaneous microwave ablation (MWA) of renal masses (RM) is still considered experimental as opposed to established procedures such as cryoablation (CA). We aimed to compare perioperative, functional and oncological outcomes of patients with RM treated with CA and MWA.

MATERIALS AND METHODS

Data from 116 (69.9%) and 50 (30.1%) patients treated with CA and MWA for RM were analyzed. Patients' demographics and perioperative data were collected including nephrometry scores, complications, pre- and postprocedural renal function. Tumor persistence and recurrence were recorded. Descriptive statistics compared functional outcomes between groups. Cox regression analyses tested risk factors associated with recurrence.

RESULTS

Groups were similar in terms of RM diameter, nephrometry scores and histology distribution. Median follow-up was 26 (13-46) and 24 (14-36) months for CA and MWA, respectively. The rate of overall (36.2% for CA vs. 24% for MWA, P= .1) and major (Clavien ≥ 3a) complications (1.7% vs. 5.4%, P = .1) were similar among groups. The median decline of renal function after 6 months follow-up did not differ between CA and MWA (P = .8). Tumor persistence [4.3% vs. 12%] and recurrence [9.5% and 7.1%] rates were similar for CA and MWA. Three years recurrence free and overall survival were 91% versus 95% (log-rank P = .77) and 80 versus 88% (log-rank P = .23) in the CA and MWA groups, respectively. At Cox analysis no predictors were found associated with recurrence.

CONCLUSION

Despite being considered still experimental, MWA showed comparable outcomes relative to CA in terms of safety, preservation of renal function and oncological efficacy.

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.