Utility of the RENAL Nephrometry Scoring System in Predicting Adverse Events and Outcomes of Percutaneous Microwave Ablation of Renal Tumors

Percutaneous Image-Guided Ablation of Renal Cancer: Traditional and Emerging Indications, Energy Sources, Techniques, and Future Developments

Percutaneous image-guided ablation (IGA) has emerged as an established alternative to surgical management for small renal masses. This comprehensive review examines traditional and emerging indications, energy sources, techniques, and future developments in IGA for renal cancer treatment. Traditionally, IGA has been indicated for frail or comorbid patients, those with solitary kidneys or chronic kidney disease, and those with histologically proven renal cell carcinomas less than 4 cm in size. Recent evidence supports expanding these indications to include T1b or T2 tumours and hereditary or recurrent renal cell carcinomas. The use of IGA combined with pre-ablation transarterial embolisation is discussed herein. This review then explores traditional energy sources including radiofrequency ablation, cryoablation, and microwave ablation, highlighting their respective advantages and limitations. Emerging technologies such as irreversible electroporation and histotripsy, as promising alternatives, are then presented, highlighting their advantage of being able to treat tumours near critical structures. Future research priorities highlight the need to establish high-quality evidence through innovative trial designs, as well as taking patient-reported outcome measures into account. Health economic considerations are key to ensuring that ablation therapies are cost-effective. The integration of artificial intelligence and radiomics shows vast potential for improving patient selection and treatment outcomes. Additionally, the immunomodulatory effects of ablative therapies suggest possible synergistic benefits when combined with immunotherapy which also require exploration in future research. Technological advancement and research developments will continue to broaden the role of IGA in clinical practice.

Early-Stage Renal Cell Carcinoma Locoregional Therapies: Current Approaches and Future Directions

Renal cell carcinoma (RCC) is the most common primary renal malignancy. Prevalence of RCC in developed countries has slowly increased. Although partial or total nephrectomy has been the first-line treatment for early-stage RCC, improved or similar safety and treatment outcomes with locoregional therapies have challenged this paradigm. In this review, we explore locoregional techniques for early-stage RCC, including radiofrequency ablation, cryoablation, and microwave ablation with a focus on procedural technique, patient selection, and safety/treatment outcomes. Furthermore, we discuss future advances and novel techniques, including radiomics, combination therapy, high-intensity focused ultrasound, and catheter-directed techniques.

Predicting Peri-Operative Outcomes in Patients Treated with Percutaneous Thermal Ablation for Small Renal Masses: The SuNS Nephrometry Score

Our objective was to develop a new, simple, and ablation-specific nephrometry score to predict peri-operative outcomes and to compare its predictive accuracy to PADUA and RENAL scores. Overall, 418 patients were treated with percutaneous thermal ablation (microwave and radiofrequency) between 2008 and 2021. The outcome of interest was trifecta status (achieved vs. not achieved): incomplete ablation or Clavien-Dindo ≥ 3 complications or postoperative estimated glomerular filtration rate decrease ≥ 30%. First, we validated the discrimination ability of the PADUA and RENAL scoring systems. Second, we created and internally validated a novel scoring (SuNS) system, according to multivariable logistic regression models. The predictive accuracy of the model was tested in terms of discrimination and calibration. Overall, 89 (21%) patients did not achieve trifecta. PADUA and RENAL scores showed poor ability to predict trifecta status (c-indexes 0.60 [0.53-0.67] and 0.62 [0.55-0.69], respectively). We, therefore, developed the SuNS model (c-index: 0.74 [0.67-0.79]) based on: (1) contact surface area; (2) nearness to renal sinus or urinary collecting system; (3) tumour diameter. Three complexity classes were created: low (3-4 points; 11% of no trifecta) vs. moderate (5-6 points; 30% of no trifecta) vs. high (7-8 points; 65% of no trifecta) complexity. Limitations include the retrospective and single-institution nature of the study. In conclusion, we developed an immediate, simple, and reproducible ablation-specific nephrometry score (SuNS) that outperformed PADUA and RENAL nephrometry scores in predicting peri-operative outcomes. External validation is required before daily practice implementation.

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.

External Validation of the Percutaneous Renal Ablation Complexity Scoring System in Patients Undergoing Percutaneous Cryoablation or Microwave Ablation of Renal Tumors

PURPOSE

To assess the ability of the Percutaneous Renal Ablation Complexity (P-RAC) scoring system to predict procedural complexity or adverse events (AEs) in adult patients undergoing percutaneous thermal ablation of renal tumors.

MATERIALS AND METHODS

A retrospective review of 240 consecutive adult patients who underwent percutaneous thermal renal ablation from 2004 to 2018 was conducted. The P-RAC score was calculated for each renal tumor and procedural complexity recorded. A correlation coefficient was calculated for the P-RAC score and both the number of probes used and procedural duration. Receiver operating characteristic curves assessed the score's ability to predict the use of adjunctive techniques and/or major AEs, classified according to the Society of Interventional Radiology guidelines.

RESULTS

For the entire cohort, there was a weak correlation between P-RAC scores and both the number of probes used (r = 0.31; P < .001) and procedural duration (r = 0.18; P = .03). When evaluating only patients treated with microwave ablation (MWA), no correlation between P-RAC scores and either the number of probes (P = .7) used or procedural duration (P = .4) was found. The area under the curve (AUC) for the P-RAC score to predict the use of adjunctive techniques was 0.55 and 0.53 for the entire cohort and MWA group, respectively. The AUC for the P-RAC score to predict major AEs was 0.70, 0.71, and 0.73 for the entire cohort, MWA group, and cryoablation group, respectively.

CONCLUSIONS

The P-RAC scoring system is limited in its ability to predict percutaneous thermal renal tumor ablation procedural complexity, especially in patients treated with MWA. The scoring system may have a role in identifying patients at risk of major AEs.