Ablative Therapies for the Treatment of Small Renal Masses: a Review of Different Modalities and Outcomes

Percutaneous Renal Tumor Cryoablation Effect on Renal Function

Background: Percutaneous cryoablation (PCA) of renal tumors is a well-established alternative to partial nephrectomy, but the effects on renal function after the procedure are not well-documented. The purpose of this study was to evaluate renal function after computed tomography-guided PCA. Materials and Methods: A retrospective cohort study including 259 patients treated with PCA at Odense University Hospital, Denmark from January 1, 2015 to December 31, 2019. Both patients with malignant (96%) and benign tumors (4%) were included. Mean age of patients was 66.5 years (standard deviation [SD] = 10.9, range: 27-91) and 174 (67%) patients were men. Baseline estimated glomerular filtration rate (eGFR) was recorded at baseline and 12 months after cryoablation. Results: Mean tumor size was 27.5 mm (SD = 10.0) distributed in seven different histopathological types, mainly clear cell renal-cell carcinoma (RCC) (64%) and papillary RCC (22%). Mean eGFR at baseline was 73.7 mL/min/1.73 m2 (SD = 23.2) with a follow-up mean eGFR of 69.7 (SD = 23.7) (p < 0.0001). At baseline before intervention 190 patients (73%) had eGFR matching chronic kidney disease (CKD) groups 1 and 2 (normal to mild CKD), 64 patients (24%) matching CKD group 3 (average CKD), and 1% in groups 4 and 5. At 12-month follow-up, 171 patients (66%) had eGFR matching CKD groups 1 and 2, 77 patients (30%) matching CKD group 3 and 11 patients (4%) matching CKD groups 4 and 5. In patients with skewed renography who had PCA in the kidney with better excretion, eGFR at baseline was 64.7 and 61.2 at follow-up (p = 0.703). Conclusions: This study showed minimal decline in renal function 12 months after PCA, even for patients with reduced renal function. PCA is therefore considered a safe and relevant intervention.

Impact of Body Mass Index on Perioperative Complications and Oncologic Outcomes in Patients Undergoing Thermal Ablation for Renal Cell Carcinoma

PURPOSE

To determine effect of body mass index (BMI) on safety and cancer-related outcomes of thermal ablation for renal cell carcinoma (RRC).

MATERIALS AND METHODS

This retrospective study evaluated 427 patients (287 men and 140 women; mean [SD] age, 72 [12] y) who were treated with thermal ablation for RCC between October 2006 and December 2017. Patients were stratified by BMI into 3 categories: normal weight (18.5-24.9 kg/m²), overweight (25-29.9 kg/m²), and obese (≥ 30 kg/m²). Of 427 patients, 71 (16%) were normal weight, 157 (37%) were overweight, and 199 (47%) were obese. Complication rates, local recurrence, and residual disease were compared in the 3 cohorts.

RESULTS

No differences in technical success between normal-weight, overweight, and obese patients were identified (P = .72). Primary technique efficacy rates for normal-weight, overweight, and obese patients were 91%, 94%, and 93% (P = .71). There was no significant difference in RCC specific-free survival, disease-free survival, and metastasis-free survival between obese, overweight, and normal-weight groups (P = .72, P = .43, P = .99). Complication rates between the 3 cohorts were similar (normal weight 4%, overweight 2%, obese 3%; P = .71).

CONCLUSIONS

CT-guided renal ablation is safe, feasible, and effective regardless of BMI.

[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.

Current opinion in urology 2017: focal therapy of small renal lesions

PURPOSE OF REVIEW

With the increasing incidence of small renal masses (SRMs), ablative technologies are becoming more commonly utilized. With any nascent treatment modality, outcomes literature needs to be constantly re-evaluated. The purpose of this review is to revisit the most updated literature regarding the safety and efficacy of ablative treatments of renal lesions.

RECENT FINDINGS

Recent literature demonstrates that small renal tumor ablation is safe and effective. Although it does not have the same oncological efficacy of surgical extirpation, local recurrence-free survival has consistently shown to be around 90%. Cryoablation and radiofrequency ablation have longer-term data demonstrating durable responses. Microwave ablation and irreversible electroporation are promising modalities with longer-term data coming. Complication rates and procedural morbidity of ablation are consistently lower than for partial nephrectomy.

SUMMARY

Image-guided focal ablation is a valuable tool in the management of SRMs. Although it does not have the same efficacy of surgical extirpation, with the ability to perform repeat procedures and salvage surgery if necessary, oncologic outcomes are comparable to those of upfront surgery. Ultimately, longer-term studies and prospective trials are needed to further elucidate these modalities.

Available ablation energies to treat cT1 renal cell cancer: emerging technologies

Purpose

An increasing interest in percutaneous ablation of renal tumors has been caused by the increasing incidence of SRMs, the trend toward minimally invasive nephron-sparing treatments and the rapid development of local ablative technologies. In the era of shared decision making, patient preference for non-invasive treatments also leads to an increasing demand for image-guided ablation. Although some guidelines still reserve ablation for poor surgical candidates, indications may soon expand as evidence for the use of the two most validated local ablative techniques, cryoablation (CA) and radiofrequency ablation (RFA), is accumulating. Due to the collaboration between experts in the field in biomedical engineering, urologists, interventional radiologists and radiation oncologists, the improvements in ablation technologies have been evolving rapidly in the last decades, resulting in some new emerging types of ablations.

Methods

A literature search was conducted to identify original research articles investigating the clinical outcomes of new emerging technologies, percutaneous MWA, percutaneous IRE and SABR, in patients with primary cT1 localized renal cell cancer.

Results

Due to the collaboration between experts in the field in biomedical engineering, urologists, interventional radiologists and radiation oncologists, the improvements in ablation technologies have been evolving rapidly in the last decades. New emerging technologies such as microwave ablation (MWA), irreversible electroporation (IRE) and stereotactic ablative radiotherapy (SABR) seem to be getting ready for prime time.

Conclusion

This topical paper describes the new emerging technologies for cT1 localized renal cell cancer and investigates how they compare to CA and RFA.

Cryoablation: a potential treatment option for renal metastasis from lung cancer?

Cryoablation is successfully performed as a treatment for small renal cancers. The occurrence of a solitary renal metastasis from lung cancer is an uncommon finding entailing a limited knowledge on the choice of its optimal treatment. We present two patients diagnosed with non-small cell lung cancer, who were initially treated with curatively intended chemoradiotherapy. In the follow-up period, a non-symptomatic solitary renal metastasis was found in both patients. Both received CT-guided cryoablation of their renal metastases. One patient was successfully treated with no relapse, whereas the other patient received re-cryoablation due to development of a new renal metastasis. In both patients, no residual tumour was found at the 3 months' follow-up examination. Whether the minimally invasive procedure of cryoablation is a feasible treatment in the management of solitary renal metastases from lung cancer is still undetermined. The recurrence and incomplete treatment are concerns requiring further research.

Treatment approaches to small renal masses in patients of advanced age (≥75 years)

The elderly population is increasing in Turkey and across the world. With the frequent use of imaging modalities, the detection rate of coincidental small renal mass has also increased. Since small renal masses are generally not malignant, most of them can be followed up by active surveillance. In the current study, we examined the treatment options that can be offered to elderly patients with small renal masses. The optimum treatment method for patients of advanced age presenting with renal masses should be determined based on the presence of comorbidities such as age, renal function, and tumor characteristics.

Thermal Ablation of T1c Renal Cell Carcinoma: A Comparative Assessment of Technical Performance, Procedural Outcome, and Safety of Microwave Ablation, Radiofrequency Ablation, and Cryoablation

PURPOSE

To evaluate perioperative outcomes of thermal ablation with microwave (MW), radiofrequency (RF), and cryoablation for stage T1c renal cell carcinoma (RCC).

MATERIALS AND METHODS

A retrospective analysis of 384 patients (mean age, 71 y; range, 22-88 y) was performed between October 2006 and October 2016. Mean radius, exophytic/endophytic, nearness to collecting system or sinus, anterior/posterior, and location relative to polar lines; preoperative aspects and dimensions used for anatomic classification; and centrality index scores were 6.3, 7.9, and 2.7, respectively. Assessment of pre- and postablation serum blood urea nitrogen, creatinine, and estimated glomerular filtration rate was performed to assess functional outcomes. Linear regression analyses were performed to compare sedation medication dosages among the three treatment cohorts. Univariable and multivariable logistic regression analyses were performed to compare rates of residual disease and complications among treatment modalities.

RESULTS

A total of 437 clinical stage T1N0M0 biopsy-proven RCCs measuring 1.2-6.9 cm were treated with computed tomography (CT)-guided MW ablation (n = 44; 10%), RF ablation (n = 347; 79%), or cryoablation (n = 46; 11%). There were no significant differences in patient demographic or tumor characteristics among cohorts. Complication rates and immediate renal function changes were similar among the three ablation modalities (P = .46 and P = .08, respectively). MW ablation was associated with significantly decreased ablation time (P < .05), procedural time (P < .05), and dosage of sedative medication (P < .05) compared with RF ablation and cryoablation.

CONCLUSIONS

CT-guided percutaneous MW ablation is comparable to RF ablation or cryoablation for the treatment of stage T1N0M0 RCC with regard to treatment response and is associated with shorter treatment times and less sedation than RF ablation or cryoablation. In addition, the safety profile of CT-guided MW ablation is noninferior to those of RF ablation or cryoablation.

Current Trends in Renal Surgery and Observation for Small Renal Masses

There has been a rising incidence of small renal masses and concomitant downward stage migration. This has led to an evolution in the management of kidney cancer from radical nephrectomy to nephron-sparing treatment options including observation. The adoption of partial nephrectomy continues to increase but is still incomplete leading to significant disparities in the delivery of care throughout the country. Surgical excision remains the treatment of choice for small kidney cancers; however, ablative therapies and active surveillance are emerging as reasonable options for select patients. With continued refinements in treatment options and improvements in ability to risk stratify SRMs, the current treatment trends will likely continue to evolve.