Sequential changes after radiofrequency ablation and cryoablation of renal neoplasms: role of CT and MR imaging

Ablative Treatments for Small Renal Masses and Management of Recurrences: A Comprehensive Review

This review focuses on ablative techniques for small renal masses (SRMs), including radiofrequency ablation (RFA), cryoablation (CA), microwave ablation (MWA), and irreversible electroporation (IRE), and discusses recurrence management. Through an extensive literature review, we outline the procedures, outcomes, and follow-up strategies associated with each ablative method. The review provides a detailed examination of these techniques-RFA, CA, MWA, and IRE-elucidating their respective outcomes. Recurrence rates vary among them, with RFA and CA showing comparable rates, MWA demonstrating favorable short-term results, and IRE exhibiting promise in experimental stages. For managing recurrences, various strategies are considered, including active surveillance, re-ablation, or salvage surgery. Surveillance is preferred post-RFA and post-CA, due to slow SRM growth, while re-ablation, particularly with RFA and CA, is deemed feasible without additional complications. Salvage surgery emerges as a viable option for larger or resistant tumors. While ablative techniques offer short-term results comparable to surgery, further research is essential to understand their long-term effects fully. Decisions concerning recurrence management should consider individual and tumor-specific factors. Imaging, notably contrast-enhanced ultrasounds, plays a pivotal role in assessing treatment success, emphasizing the necessity of a multidisciplinary approach for optimal outcomes. The lack of randomized trials highlights the need for further research.

Contrast enhancement early after renal malignancy cryoablation: imaging findings associated with benignity

OBJECTIVES

Contrast enhancement by MRI done early after cryoablation for renal malignancies may suggest residual tumor (RT). However, we have observed MRI enhancement within 48 h of cryoablation in patients who had no contrast enhancement 6 weeks later. Our purpose was to identify features of 48-h contrast enhancement in patients without RT.

METHODS

This single-center retrospective study included consecutive patients who underwent percutaneous cryoablation of renal malignancies in 2013-2020, exhibited cryoablation-zone MRI contrast enhancement 48 h later, and had available 6-week MRI scans. Persistent or growing CE at 6 weeks vs. 48 h was classified as RT. A washout index was calculated for each 48-h MRI, and its performance for predicting RT was assessed by receiver operating characteristic curve analysis.

RESULTS

We included 60 patients with 72 cryoablation procedures and 83 cryoablation zones exhibiting 48-h contrast enhancement; mean age was 66 ± 17 years. Clear-cell renal cell carcinoma accounted for 95% of tumors. Of the 83 48-h enhancement zones, RT was observed in eight while 75 were benign. The 48-h enhancement was consistently visible at the arterial phase. Washout was significantly associated with RT (p < 0.001) and gradually increasing contrast enhancement with benignity (p < 0.009). A washout index below  - 1.1 predicted RT with 88% sensitivity and 84% specificity.

CONCLUSION

MRI contrast enhancement 48 h after cryoablation of renal malignancies was usually benign. Washout was associated with residual tumor, with a washout index value below  - 1.1 exhibiting good performance in predicting residual tumor. These findings may help to guide decisions about repeat cryoablation.

CLINICAL RELEVANCE STATEMENT

Magnetic resonance imaging contrast enhancement 48 h after cryoablation of renal malignancies rarely indicates residual tumor, which is characterized by washout with a washout index lower than  - 1.1.

KEY POINTS

• Contrast enhancement at the arterial phase of magnetic resonance imaging done 48 h after cryoablation of a renal malignancy is usually benign. • Residual tumor manifesting as contrast enhancement at the arterial phase is characterized by subsequent marked washout. • A washout index below  - 1.1 has 88% sensitivity and 84% specificity for residual tumor.

Phase 2 Trial of Stereotactic Ablative Radiotherapy for Patients with Primary Renal Cancer

BACKGROUND

Most renal cell carcinomas (RCCs) are localized and managed by active surveillance, surgery, or minimally invasive techniques. Stereotactic ablative radiation (SAbR) may provide an innovative non-invasive alternative although prospective data are limited.

OBJECTIVE

To investigate whether SAbR is effective in the management of primary RCCs.

DESIGN, SETTING, AND PARTICIPANTS

Patients with biopsy-confirmed radiographically enlarging primary RCC (≤5 cm) were enrolled. SAbR was delivered in either three (12 Gy) or five (8 Gy) fractions.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

The primary endpoint was local control (LC) defined as a reduction in tumor growth rate (compared with a benchmark of 4 mm/yr on active surveillance) and pathologic evidence of tumor response at 1 yr. Secondary endpoints included LC by the Response Evaluation Criteria in Solid Tumors (RECIST 1.1), safety, and preservation of kidney function. Exploratory tumor cell-enriched spatial protein and gene expression analysis were conducted on pre- and post-treatment biopsy samples.

RESULTS AND LIMITATIONS

Target accrual was reached with the enrollment of 16 ethnically diverse patients. Radiographic LC at 1 yr was observed in 94% of patients (15/16; 95% confidence interval: 70, 100), and this was accompanied by pathologic evidence of tumor response (hyalinization, necrosis, and reduced tumor cellularity) in all patients. By RECIST, 100% of the sites remained without progression at 1 yr. The median pretreatment growth rate was 0.8 cm/yr (interquartile range [IQR]: 0.3, 1.4), and the median post-treatment growth rate was 0.0 cm/yr (IQR: -0.4, 0.1, p < 0.002). Tumor cell viability decreased from 4.6% to 0.7% at 1 yr (p = 0.004). With a median follow-up of 36 mo for censored patients, the disease control rate was 94%. SAbR was well tolerated with no grade ≥2 (acute or late) toxicities. The average glomerular filtration rate declined from a baseline of 65.6 to 55.4 ml/min at 1 yr (p = 0.003). Spatial protein and gene expression analyses were consistent with the induction of cellular senescence by radiation.

CONCLUSIONS

This clinical trial adds to the growing body of evidence suggesting that SAbR is effective for primary RCC supporting its evaluation in comparative phase 3 clinical trials.

PATIENT SUMMARY

In this clinical trial, we investigated a noninvasive treatment option of stereotactic radiation therapy for the treatment of primary kidney cancer and found that it was safe and effective.

Intraoperative MRI-derived volumetric ablation margins and initial correlation with local outcome after MRI-guided cryoablation of renal tumors

PURPOSE

To assess volumetric ablation margins derived from intraoperative pre- and post-ablation MRI after magnetic resonance imaging (MRI)-guided percutaneous cryoablation of renal tumors and explore its correlation with local treatment success.

METHODS

Retrospective analysis was performed on 30 patients (mean age 69y) who underwent percutaneous MRI-guided cryoablation between May 2014 and May 2020 for 32 renal tumors (size: 1.6-5.1 cm). Tumor and ice-ball volumes were segmented on intraprocedural pre- and post-ablation MR images using Software Assistant for Interventional Radiology (SAFIR) software. After MRI-MRI co-registration, the software automatically quantified the minimal treatment margin (MTM),defined as the smallest 3D distance between the tumor and ice-ball surface. Local tumor progression (LTP) after cryoablation was assessed on follow-up imaging.

RESULTS

Median follow-up was 16 months (range: 1-58). Local control after cryoablation was achieved in 26 cases (81%) while LTP occurred in 6 (19%). The intended MTM of ≥5 mm was achieved in 3/32 (9%) cases. Median MTM was significantly smaller for cases with (- 7 mm; IQR:-10 to - 5) vs. without LTP (3 mm; IQR:2 to 4) (P < .001). All cases of LTP had a negative MTM. All negative treatment margins occurred in tumors > 3 cm.

CONCLUSIONS

Determination of volumetric ablation margins from intraoperative MRI was feasible and may be useful in predicting local outcome after MRI-guided renal cryoablation. In our preliminary data, an intraoperative MRI-derived minimal margin extending at least 1 mm beyond the MRI-visible tumor led to local control and this was more difficult to achieve in tumors > 3 cm. Ultimately, online margin analysis may be a valuable tool to intraoperatively assess therapy success, but larger prospective studies are needed to establish a reliable threshold for clinical use.

Time-course changes in multiparametric magnetic resonance imaging following focal cryotherapy for localized prostate cancer: Initial experience

PURPOSE

To evaluate the time-course changes of multiparametric MRI findings following focal cryotherapy for localized prostate cancer.

METHODS

Sixteen patients who underwent focal cryotherapy as an initial curative treatment for localized prostate cancer during March 2017-April 2021 were included. Before the treatment, the patients underwent targeted prostate biopsy using MRI-transrectal ultrasound fusion. Overall, 64 MRIs were conducted after focal cryotherapy and the temporal post-treatment MR signal changes of the ablated area in T2WI, T1WI, DWI, and DCE-MRI were analyzed.

RESULTS

Technical success was achieved in all patients. The median follow-up period was 22 months. The initial post-treatment MRI revealed significant signal changes in the target lesions for all patients, including the disappearance of findings suggestive of cancer. At 3 months post-treatment, most lesions were hyperintense with a hypointense rim on T2WI, T1WI, and DWI (83.3 %). After 6 months, hyperintensity reduced, and after 17 months, all lesions showed hypointensity in these sequences. DCE-MRI of most patients showed loss of internal enhancement; however, one patient exhibited residual nodular enhancement in the ablated area at 3 months, which disappeared after 6 months. Peripheral enhancement was common at 3 months, disappearing after 23 months. Two patients showed biopsy-evidenced local recurrence. The recurrent lesions showed hypointensity on T2WI with diffusion restriction and early contrast enhancement in the ventral transition zone.

CONCLUSION

MRI findings of the ablated sites following focal cryotherapy for localized prostate cancer show dynamic signal changes, especially within the first 6 months.

Correlation between renal ablation zone in contrast-enhanced CT and non-enhanced MRI during the early period following percutaneous cryoablation

Purpose

To retrospectively evaluate and correlate the contrast-enhanced computed tomography (CECT) and non-enhanced magnetic resonance imaging (MRI) during the early period following renal cryoablation.

Materials and methods

Both dynamic CECT and non-enhanced MRI were performed within 4 days following cryoablation in 34 renal tumors in 33 patients. The renal volumes of the unenhanced regions on dynamic CECT (nephrogenic phase, 4 mm thickness) and the regions with signal intensity changes on non-enhanced MRI (fat-suppressed T2-weighted image, 4 mm thickness) were evaluated. Fusion images of the axial, coronal, and sagittal sections of CECT and MRI images were created from the maximum cross-section of the renal tumor, and the match score of each image was visually evaluated on a 5-point scale.

Results

The mean renal volume of the unenhanced regions on CECT and those with signal intensity changes on non-enhanced MRI following cryoablation were 29.5 ± 19.9 cm³ (range, 4.3–97.4 cm³) and 30.7 ± 19.8 cm³ (range, 6.7–94.0 cm³), respectively; the difference between them was –1.17 cm³ (95% confidence interval [CI] –2.74, 0.40, P = 0.139). The Pearson’s product-moment correlation coefficient (r = 0.975; 95% CI, 0.951, 0.988; P < 0.0001) showed a strong correlation between the volumes. The average match score between CECT and non-enhanced MRI was as high as 4.5 ± 0.5 points (radiologist 1, 4.3 ± 0.5; radiologist 2, 4.7 ± 0.5). Local tumor control rate was 94.1% (32/34 tumors) and recurrence-free survival rate was 82.0% (95% CI: 64.2%, 91.5%) at 5 years.

Conclusions

The region with signal intensity changes on non-enhanced MRI was strongly correlated with the unenhanced region on CECT during the early period following renal cryoablation.

Imaging considerations for thermal and radiotherapy ablation of primary and metastatic renal cell carcinoma

Ablative (percutaneous and stereotactic) thermal and radiotherapy procedures for management of both primary and metastatic renal cell carcinoma are increasing in popularity in clinical practice. Data suggest comparable efficacy with lower cost and morbidity compared to nephrectomy. Ablative therapies may be used alone or in conjunction with surgery or chemotherapy for treatment of primary tumor and metastatic disease. Imaging plays a crucial role in pre-treatment selection and planning of ablation, intra-procedural guidance, evaluation for complications, short- and long-term post-procedural surveillance of disease, and treatment response. Treatment response and disease recurrence may differ considerably after ablation, particularly for stereotactic radiotherapy, when compared to conventional surgical and chemotherapies. This article reviews the current and emerging role of imaging for ablative therapy of renal cell carcinoma.

CT evaluation of patent artery after percutaneous cryoablation of renal cell carcinoma

PURPOSE

The purpose of this retrospective study was to determine the incidence of persistent patent artery after percutaneous cryoablation of renal cell carcinoma (RCC) and the relationship between patent arteries one month after cryoablation and early tumor progression.

MATERIALS AND METHODS

One hundred and fifty-nine patients (112 men, 47 women; mean age, 63.6±14.6 [SD] years; age range: 21-91 years) who underwent percutaneous cryoablation for 186 RCCs (mean diameter, 1.9±0.6 [SD] cm; range: 0.7-4.0cm) were retrospectively included. After cryoablation, patients underwent contrast-enhanced computed tomography (CT) with ≤2-mm slice thickness within one week from cryoablation, and at one, three, and six months. The time course of patent artery in the ablated renal parenchyma after cryoablation was the primary endpoint. The relationships between patent arteries one month after cryoablation and treatment effectiveness, tumor vascularity, tumor enhancement one month after cryoablation, tumor subtype, and renal function changes were evaluated as secondary endpoints.

RESULTS

CT showed patent arteries in the ablated renal parenchyma within one week in 166 RCCs (89.2%), at one month in 54 RCCs (29.0%), at three months in 8 RCCs (4.3%), and at six months in 2 RCCs (1.1%). The presence of patent artery one month after cryoablation was significantly associated with tumor enhancement at the same time point (P=0.015). There was no association between patent arteries one month after cryoablation and treatment effectiveness (P=0.693).

CONCLUSION

Patent arteries in the ablated renal parenchyma are commonly observed on CT examination after percutaneous cryoablation of RCC. However, they gradually disappear and do not require specific treatment.

Current management of small renal masses

One of the consequences of the growing use of diagnostic imaging techniques is the notable growth in the detection of small renal masses presumably corresponding to localized tumors that are potentially curable with surgical treatment. When faced with the finding of a small renal mass, radiologists must determine whether it is benign or malignant, and if it is malignant, what subtype it belong to, and whether it should be managed with surgical treatment, with ablative techniques, or with watchful waiting with active surveillance. Small renal masses are now a clinical entity that require management different from the approaches used for classical renal cell carcinomas. In this scenario, radiologists are key because they are involved in all aspects of the management of these tumors, including in their diagnosis, treatment, and follow-up.

Follow-up imaging after cryoablation of clear cell renal cell carcinoma is feasible using single photon emission computed tomography with 111In-girentuximab

Purpose

Detection of residual or recurrent vital renal tumor on follow-up (FU) cross-sectional imaging after ablative therapy is challenging. The specific and high expression levels of carbonic anhydrase IX (CAIX) in clear cell renal cell carcinoma (ccRCC) makes it a suitable target for imaging using radiolabeled anti-CAIX antibody girentuximab. The objective of this study was to evaluate the feasibility of targeted FU imaging 1 month after cryoablation of ccRCC using single photon emission computed tomography (SPECT) after ¹¹¹In-labeled girentuximab administration.

Methods

In this prospective study 16 patients underwent ¹¹¹In-girentuximab-SPECT before MR-guided renal cryoablation between February 2015 and September 2018. In case of tumor targeting ¹¹¹In-girentuximab-SPECT was repeated 1 month following MR-guided cryoablation. Presence of residual or recurrent vital tumor was assessed on contrast-enhanced cross-sectional imaging during further FU. The standard FU imaging protocol consisted of MRI/CT scans at 1, 3, 6, 12, and 18 months and annually thereafter.

Results

A total of 10 (63%) patients showed positive tumor targeting on ¹¹¹In-girentuximab-SPECT before cryoablation and 9 ( 56%) were eligible to undergo FU SPECT. Of the 9 ¹¹¹In-girentuximab-SPECT FU scans, 8 (89%) were considered negative. One (11%) scan showed uptake suggestive for residual vital tumor. Six months after treatment, FU CT showed contrast enhancement suggestive for residual/recurrent disease in the ablated zone at the site of the ¹¹¹In-girentuximab uptake after treatment. During a mean FU of 21 months (range 1–33) no other cases with residual/recurrent disease were detected.

Conclusion

FU imaging with ¹¹¹In-girentuximab-SPECT is feasible after ccRCC cryoablation and may contribute to early detection of residual or recurrent disease.

Sonographic Evaluation of Genitourinary Inflammatory Pseudotumors and Its Mimics

Inflammatory pseudotumor is a relatively rare, nonneoplastic lesion composed of inflammatory cells and myofibroblastic spindle cells that can be identified on sonographic evaluation of the genitourinary system. These lesions are thought to be an inflammatory response to insults such as surgery, trauma, infection, or malignancy. Such lesions need to be distinguished from true neoplasms and other benign lesions, including inflammatory responses and infectious processes. Identification of inflammatory pseudotumors and its mimics is important for radiologists to guide patient treatment and follow-up. This pictorial essay presents sonographic features of inflammatory pseudotumors of the genitourinary tract and its mimics with cross-sectional imaging and histopathology, where available.

Imaging after radiofrequency ablation of renal tumors

The number of percutaneous radiofrequency ablation procedures performed for renal tumors is progressively increasing worldwide. Periodic imaging follow-up has the double role to guarantee the treatment efficacy over time and to early detect any possible complication. Tumor size reductions, as well as the appearance of the characteristic ‘halo sign’, are normal findings that represent good ablative outcomes. However the most reliable factor of ablation efficacy remains the total absence of contrast enhancing zones within the ablated area. The aim of this article is to illustrate the typical aspect of an effective radiofrequency ablation treatment, which are the imaging findings that may suggest the presence of residual tumoral tissue and which are the main early and late procedural complications.

Imaging for the diagnosis and response assessment of renal tumours

PURPOSE

Imaging plays a key role throughout the renal cell carcinoma (RCC) patient pathway, from diagnosis and staging of the disease, to the assessment of response to therapy. This review aims to summarise current knowledge with regard to imaging in the RCC patient pathway, highlighting recent advances and challenges.

METHODS

A literature review was performed using Medline. Particular focus was paid to RCC imaging in the diagnosis, staging and response assessment following therapy.

RESULTS

Characterisation of small renal masses (SRM) remains a diagnostic conundrum. Contrast-enhanced ultrasound (CEUS) has been increasingly applied in this field, as have emerging technologies such as multiparametric MRI, radiomics and molecular imaging with 99mtechnetium-sestamibi single photon emission computed tomography/CT. CT remains the first-line modality for staging of locoregional and suspected metastatic disease. Although the staging accuracy of CT is good, limitations in determining nodal status persist. Response assessment following ablative therapies remains challenging, as reduction in tumour size may not occur. The pattern of enhancement on CT may be a more reliable indicator of treatment success. CEUS may also have a role in monitoring response following ablation. Response assessments following anti-angiogenic and immunotherapies in advanced RCC is an evolving field, with a number of alternative response criteria being proposed. Tumour response patterns may vary between different immunotherapy agents and tumour types; thus, future response criteria modifications may be inevitable.

CONCLUSION

The diagnosis and characterisation of SRM and response assessment following targeted therapy for advanced RCC are key challenges which warrant further research.

Is there a role for perfusion imaging in assessing treatment response following ablative therapy of small renal masses-A systematic review

Aims

Ablation therapies are an innovative nephron-sparing alternative to radical nephrectomy for early stage renal cancers, although determination of treatment success is challenging. We aimed to undertake a systematic review of the literature to determine whether assessment of tumour perfusion may improve response assessment or alter clinical management when compared to standard imaging.

Material and Methods

Two radiologists performed independent primary literature searches for perfusion imaging in response assessment following ablative therapies (radiofrequency ablation and cryotherapy) focused on renal tumours.

Results

5 of 795 articles were eligible, totaling 110 patients. The study designs were heterogeneous with different imaging techniques, perfusion calculations, reference standard and follow-up periods. All studies found lower perfusion following treatment, with a return of ‘high grade’ perfusion in the 7/110 patients with residual or recurrent tumour. One study found perfusion curves were different between successfully ablated regions and residual tumour.

Conclusions

Studies were limited by small sample size and heterogeneous methodology. No studies have investigated the impact of perfusion imaging on management. This review highlights the current lack of evidence for perfusion imaging in response assessment following renal ablation, however it suggests that there may be a future role. Further prospective research is required to address this.

Focal ablation therapy for renal cancer in the era of active surveillance and minimally invasive partial nephrectomy

Partial nephrectomy is the optimal surgical approach in the management of small renal masses (SRMs). Focal ablation therapy has an established role in the modern management of SRMs, especially in elderly patients and those with comorbidities. Percutaneous ablation avoids general anaesthesia and laparoscopic ablation can avoid excessive dissection; hence, these techniques can be suitable for patients who are not ideal surgical candidates. Several ablation modalities exist, of which radiofrequency ablation and cryoablation are most widely applied and for which safety and oncological efficacy approach equivalency to partial nephrectomy. Data supporting efficacy and safety of ablation techniques continue to mature, but they originate in institutional case series that are confounded by cohort heterogeneity, selection bias, and lack of long-term follow-up periods. Image guidance and surveillance protocols after ablation vary and no consensus has been established. The importance of SRM biopsy, its optimal timing, the type of biopsy used, and its role in treatment selection continue to be debated. As safety data for active surveillance and experience with minimally invasive partial nephrectomy are expanding, the role of focal ablation therapy in the treatment of patients with SRMs requires continued evaluation.

Clinical Practice Guidelines for Cryosurgery of Pancreatic Cancer: A Consensus Statement From the China Cooperative Group of Cryosurgery on Pancreatic Cancer, International Society of Cryosurgery, and Asian Society of Cryosurgery

Pancreatic cancer (PC), one of the most lethal malignancies, accounts for 8% to 10% of digestive system cancers, and the incidence is increasing. Surgery, chemotherapy, and radiotherapy have been the main treatment methods but are not very effective. Cryosurgery was first used in 1984 for treatment of locally advanced PC and has since become a considerable treatment for most cases of unresectable PC. During the past decade, cryosurgery has been applied in some hospitals in China, and the newly developed technique of computed tomography- and/or ultrasound-guided percutaneous cryosurgery has shown better results than chemotherapy in cases of unresectable locally advanced PC, with the 1-year survival rate reported to be more than 50%. To develop standardized criteria for the application of cryosurgery in PC, the International Society of Cryosurgery and Asian Society of Cryosurgery assembled experts from Austria, Japan, and China to discuss treatment methods and arrive at a consensus on the indications, contraindications, and preferred techniques of PC cryosurgery.

Percutaneous Cryoablation of Renal Tumors: Is It Time for a New Paradigm Shift?

PURPOSE

To retrospectively assess long-term outcomes of percutaneous renal cryoablation, including factors affecting complications and local recurrence rates.

MATERIALS AND METHODS

A total of 357 computed tomographic (CT) fluoroscopy-guided percutaneous cryoablation procedures were performed for 382 masses in 302 outpatients; 347 were biopsy-proven renal-cell carcinoma (RCC) or Bosniak category > III masses (n = 28). Benign pathologic conditions (n = 18) or metastatic non-RCC disease (n = 17) were included to analyze procedural complication rate, but recurrence rates, tumor staging, and nephrometry score were limited to RCCs. The average tumor diameter was 2.9 cm (range, 1-10.3 cm), and median nephrometry score for RCC was 8 (mean, 7.4). Protection of adjacent vital structures was performed in 34% of procedures (n = 121), and ureteral stent placement was performed for 9.2% (n = 33). All major complications were graded per surgical Clavien-Dindo criteria.

RESULTS

The average CT-visible cryoablation zone diameter was 5 cm (range, 2.5-10.5 cm). Grade ≥ 3 complications occurred in 2.8% of procedures (n = 10), and appeared related to only high nephrometry scores (P = .0086) and larger tumors (P = .0034). No significant changes in renal function before and after the procedure were noted (P = .18). At a mean follow-up of 31.8 months, the local tumor recurrence rate was 3.2% (11 of 347) for RCC, and no significant difference was noted between tumors larger or smaller than 3 cm (P = .15). The difference reached significance only among the small number of stage ≥ T2 RCC tumors (P = .0039).

CONCLUSIONS

Long-term follow-up of percutaneous renal cryoablation demonstrates low recurrence rates with preserved renal function, even for patients with high nephrometry scores and body mass index, assuming thorough cytotoxic technique and protection measures.

Renal cell carcinoma: staging and surveillance

Renal cell carcinoma is a common malignancy with many histologic subtypes. Appropriate treatment depends not only upon the specific subtype but also the size of the tumor and extent of spread at time of presentation. Approximately 5% of RCCs are part of a hereditary syndrome which must also be considered in the therapeutic decisions. Although some RCCs are detected with ultrasound, CT or MR is required for staging. CT is used most commonly as it is most readily available and relatively less expensive than MR imaging. The TNM classification of the American Joint Committee on Cancer has largely replaced the Robson classification. Early detection, accurate staging, and improved treatment options have resulted in improved 5-year survival of patients with renal carcinoma.

Dual-energy CT after radiofrequency ablation of liver, kidney, and lung lesions: a review of features

Early detection of residual tumour and local tumour progression (LTP) after radiofrequency (RF) ablation is crucial in the decision whether or not to re-ablate. In general, standard contrast-enhanced computed tomography (CT) is used to evaluate the technique effectiveness; however, it is difficult to differentiate post-treatment changes from residual tumour. Dual-energy CT (DECT) is a relatively new technique that enables more specific tissue characterisation of iodine-enhanced structures because of the isolation of iodine in the imaging data. Necrotic post-ablation zones can be depicted as avascular regions by DECT on greyscale- and colour-coded iodine images. Synthesised monochromatic images from dual-energy CT with spectral analysis can be used to select the optimal keV to achieve the highest contrast-to-noise ratio between tissues. This facilitates outlining the interface between the ablation zone and surrounding tissue. Post-processing of DECT data can lead to an improved characterisation and delineation of benign post-ablation changes from LTP. Radiologists need to be familiar with typical post-ablation image interpretations when using DECT techniques. Here, we review the spectrum of changes after RF ablation of liver, kidney, and lung lesions using single-source DECT imaging, with the emphasis on the additional information obtained and pitfalls encountered with this relatively new technique.

Teaching Points

•Technical success of RF ablation means complete destruction of the tumour.

•Assessment of residual tumour on contrast-enhanced CT is hindered by post-ablative changes.

•DECT improves material differentiation and may improve focal lesion characterisation.

•Iodine maps delineate the treated area from the surrounding parenchyma well.

Radiofrequency thermal ablation of renal tumors

Percutaneous radiofrequency ablation (PRFA) of renal malignancies is currently a therapeutic option for patients who are not able to undergo surgery. Some authors consider PRFA as the therapeutic standard in the treatment of renal neoplasms in non-operable patients due to comorbid conditions and in patients with mild-moderate renal failure, to preserve residual renal functionality. The use of PRFA has become more and more widespread due to a rise in the incidental detection of renal cell carcinomas with the ever-increasing use of Imaging for the study of abdominal diseases. Clinical studies indicate that RF ablation is an effective therapy with a low level of risk of complications, which provides good results in selected patients over short and medium term periods of time, however up to now few long-term studies have been carried out which can confirm the effectiveness of PRFA.

Percutaneous ablation for small renal masses-imaging follow-up

Image-guided percutaneous thermal ablation is a safe and effective nephron-sparing alternative to surgical resection for the treatment of small renal tumors. Assessment of treatment efficacy relies heavily on interval follow-up imaging after treatment. Contrast-enhanced computed tomography (CT) and magnetic resonance imaging (MRI) both play a pivotal role in evaluating the treatment zone, identifying residual tumor, and detecting early and delayed procedure-related complications. This article discusses a surveillance imaging protocol for patients who undergo percutaneous thermal ablation of renal tumors, and also illustrates the typical appearances of both successfully treated tumors and residual disease on contrast-enhanced CT or MRI. In addition, it discusses the imaging appearance of potential early and delayed treatment-related complications to facilitate their prompt detection and management.

Comparison of Contrast-Enhanced Ultrasound Scan (CEUS) and MRI in the follow-up of cryoablation for small renal tumors. Experience on 25 cases

Introduction

Percutaneous ablation in the kidney is now performed as a standard therapeutic nephron-sparing option in patients who are poor candidates for resection. Its increasing use has been largely prompted by the rising incidental detection of renal cell carcinomas with cross-sectional imaging and the need to preserve renal function in patients with comorbid conditions, multiple renal cell carcinomas, and/or heritable renal cancer syndromes. To date, clinical studies indicate that cryoablation is an effective therapy with acceptable short- to intermediate-term outcomes and with a low risk in the appropriate setting. This article focuses on the efficiency of contrast enhanced ultrasound scan (CEUS) as compared to contrast enhanced magnetic resonance imaging (MRI) during the follow-up after cryoablation of small renal tumors.

Material and Methods

In our Department, percutaneous or laparoscopic assisted cryoablation is offered in the treatment of small renal masses. Between January 2009 and January 2013, 25 patients (pts) were treated with laparoscopic assisted cryoablation or percutaneous cryoablation for renal tumors <3.5 cm in pts unfit for surgery. All pts had severe comorbidities (ASA score 3). Transperitoneal laparoscopic approach was performed in 11 pts, extraperitoneal approach in 3 pts, percutaneous technique was performed in 11 patients. “Tru-cut biopsy” of the renal mass was always performed before cryoablation. The SeedNet system (Galil Medical, Arden Hills, MN) was used in 12/25 pts; the Precise system (Galil Medical, Arden Hills, MN) was used in 13/25 pts. In all cases, IceRod needles were used. Real-time ultrasound guidance was used to localize the tumour and to monitor the progression of “iceball”. A double “freeze-thaw cycle” was used. All pts had MRI and CEUS before cryoablation and the follow-up consisted in CEUS/MRI every 3 months during the first year and every 6 months thereafter.

Results

The mean age of the 25 pts was 67.7 years (range 56–79); 5 pts were females and 20 were males. The mean tumor size was 2.8 cm (range 1.5–3.5). No patient required conversion to open procedure. 19 tumors were located at the lower pole, 4 were interpolar and 2 tumors were located at the upper pole. There were no intraoperative complications. The mean hospital stay was 4 days (range 1–7). Two pts required a blood transfusion; there was no statistically significant difference between preoperative and postoperative serum creatinine levels. The biopsy showed RCC in all cases. In 24/25 patients both CEUS and MRI showed no enhancement. In 1/25 pts, during the follow-up, CEUS and MRI showed a well visible recurrence at the perfusion study. It was histologically confirmed. The final results of CEUS and MRI were concordant in all pts.

Conclusions

CEUS is effective during the follow-up of renal tumor cryoablation. It could be an alternative technique to standard CT and MRI, with some advantages: low cost, short time consuming procedure, no radiation exposure, reduced amount of contrast agent (1–2 mL) and rare adverse reactions.

Management of renal tumors in Von Hippel-Lindau disease by percutaneous CT fluoroscopic guided radiofrequency ablation: preliminary results

We evaluated the feasibility and safety of percutaneous radiofrequency (RF) ablation of renal cell carcinomas (RCCs) in patients with Von Hippel-Lindau (VHL) disease. A total of 12 RCCs were treated by RF ablation in 7 patients with VHL disease. RF electrodes were placed under CT fluoroscopic guidance with conscious sedation. Technical success, technical effectiveness (disappearance of tumor enhancement), local tumor progression, complications and change in the estimated glomerular filtration rate (eGFR) were evaluated. A total of 9 sessions were undertaken. All procedures were performed with a planned protocol with a technical success rate of 100%. Tumor enhancement disappeared in all 12 tumors indicating a technical effectiveness rate of 100%. Local tumor progression was not found in any patient during the mean follow-up of 22 ± 11 months (range 12-46 months). There were no complications related to the RF procedures. The mean eGFR decreased from 65.3 ± 10.9 ml/min (range 48.5-77.5 ml/min) to 60.3 ± 11.3 ml/min (range, 45.8-73.4 ml/min, P < 0.03). The mean percentage decrease in eGFR after the last ablation was 7.6% (range 0-21.6%). Renal RF ablation is a safe and effective treatment for renal tumours that may allow patients with VHL disease to avoid major surgical interventions.

Percutaneous ablation in the kidney

Percutaneous ablation in the kidney is now performed as a standard therapeutic nephron-sparing option in patients who are poor candidates for resection. Its increasing use has been largely prompted by the rising incidental detection of renal cell carcinomas with cross-sectional imaging and the need to preserve renal function in patients with comorbid conditions, multiple renal cell carcinomas, and/or heritable renal cancer syndromes. Clinical studies to date indicate that radiofrequency ablation and cryoablation are effective therapies with acceptable short- to intermediate-term outcomes and with a low risk in the appropriate setting, with attention to pre-, peri-, and postprocedural detail. The results following percutaneous radiofrequency ablation and cryoablation in the treatment of renal cell carcinoma are reviewed in this article, including those of several larger scale studies of ablation of T1a tumors. Clinical and technical considerations unique to ablation in the kidney are presented, and potential complications are discussed.

Percutaneous radiofrequency ablation of renal cell carcinomas in patients with von Hippel Lindau disease previously undergoing a radical nephrectomy or repeated nephron-sparing surgery

BACKGROUND

Radiofrequency ablation (RFA) is accepted as a minimally invasive treatment of renal cell carcinoma (RCC). However, RFA is not fully evaluated for treating RCC in patients with von Hippel Lindau (VHL) disease who cannot undergo surgery due to serious postoperative morbidity or mortality.

PURPOSE

To evaluate the role of RFA of RCC in patients with VHL disease previously undergoing renal surgery.

MATERIAL AND METHODS

Percutaneous RFA was performed for treating 14 RCCs in six patients who had undergone radical nephrectomy (n = 3) or repeated nephron-sparing surgery (n = 3). Treatment feasibility, complications, outcome, and the change of renal function were evaluated.

RESULTS

To completely ablate 14 RCCs, 23 ablations during 12 sessions were necessary. Of 14 RCCs, nine were in proximity (<5 mm) to one or more following organs: bowel (n = 4), ureteropelvic junction or pelvis (n = 2), psoas muscle (n = 2), vascular pedicle (n = 1), and pancreas (n = 1). Of 12 sessions, one major complication (pneumothorax) developed in one session (8%). No residual or recurrent tumors were identified at the ablation areas. However, new three solid tumors less than 1 cm in diameter developed during the follow-up period but ablation was withheld until these tumors had grown to more than 1 cm in size. The mean level of serum creatinine increased with 6.4% and the mean estimated glomerular filtration rate decreased by 12.8% after the last ablation compared to those before the initial ablation (P < 0.05).

CONCLUSION

Despite technical difficulties, percutaneous RFA is a promising treatment for VHL patients who cannot undergo surgery because of excellent treatment outcome and minimal change of renal function.

Imaging in interventional oncology

Medical imaging in interventional oncology is used differently than in diagnostic radiology and prioritizes different imaging features. Whereas diagnostic imaging prioritizes the highest-quality imaging, interventional imaging prioritizes real-time imaging with lower radiation dose in addition to high-quality imaging. In general, medical imaging plays five key roles in image-guided therapy, and interventional oncology, in particular. These roles are (a) preprocedure planning, (b) intraprocedural targeting, (c) intraprocedural monitoring, (d) intraprocedural control, and (e) postprocedure assessment. Although many of these roles are still relatively basic in interventional oncology, as research and development in medical imaging focuses on interventional needs, it is likely that the role of medical imaging in intervention will become even more integral and more widely applied. In this review, the current status of medical imaging for intervention in oncology will be described and directions for future development will be examined.

Thermal ablation of renal cell carcinoma: triage, treatment, and follow-up

The incidence of renal cell carcinoma (RCC) is increasing. With the increasing emphasis on minimally invasive nephron-sparing surgery, thermal ablation is playing a larger role in the management of patients with this disease. This review outlines imaging management, intraoperative and percutaneous ablation, and postprocedural follow-up of RCC.

Morphological and functional MDCT: problem-solving tool and surrogate biomarker for hepatic disease clinical care and drug discovery in the era of personalized medicine

This article explains the significant role of morphological and functional multidetector computer tomography (MDCT) in combination with imaging postprocessing algorithms served as a problem-solving tool and noninvasive surrogate biomarker to effectively improve hepatic diseases characterization, detection, tumor staging and prognosis, therapy response assessment, and novel drug discovery programs, partial liver resection and transplantation, and MDCT-guided interventions in the era of personalized medicine. State-of-the-art MDCT depicts and quantifies hepatic disease over conventional CT for not only depicting lesion location, size, and extent but also detecting changes in tumor biologic behavior caused by therapy or tumor progression before morphologic changes. Color-encoded parameter display provides important functional information on blood flow, permeability, leakage space, and blood volume. Together with other relevant biomarkers and genomics, the imaging modality is being developed and validated as a biomarker to early response to novel, targeted anti-VEGF(R)/PDGFR or antivascular/angiogenesis agents as its parameters correlate with immunohistochemical surrogates of tumor angiogenesis and molecular features of malignancies. MDCT holds incremental value to World Health Organization response criteria and Response Evaluation Criteria in Solid Tumors in liver disease management. MDCT volumetric measurement of future remnant liver is the most important factor influencing the outcome of patients who underwent partial liver resection and transplantation. MDCT-guided interventional methods deliver personalized therapies locally in the human body. MDCT will hold more scientific impact when it is fused with other imaging probes to yield comprehensive information regarding changes in liver disease at different levels (anatomic, metabolic, molecular, histologic, and other levels).

Minimally invasive treatment of small renal tumors: trends in renal cancer diagnosis and management

Renal cell carcinoma is a common malignancy causing significant mortality. In recent years abdominal imaging, often for alternate symptomatology, has led the trend toward the detection and confirmation of smaller renal tumors. This has permitted the greater use of localized and nephron-sparing techniques including partial nephrectomy and image-guided ablation. This article aims to review the current role of image-guided biopsy and ablation in the management of small renal tumors. The natural history of renal cell carcinoma, the role of renal biopsy, the principles and procedural considerations of thermal energy ablation, and the oncological outcomes of these minimally invasive treatments are discussed and illustrated with cases from the authors' institution. Image-guided ablation, in particular, has changed the treatment paradigm and, by virtue of its increasingly evident efficacy and low morbidity, now favors the treatment of smaller tumors in patients previously unfit for surgery.

Imaging renal cell carcinoma with ultrasonography, CT and MRI

The increased use of abdominal imaging techniques for a variety of indications has contributed to more-frequent detection of renal cell carcinoma (RCC). Ultrasonography has been used to characterize the solid versus cystic nature of renal masses. This modality has limitations, however, in further characterization of solid tumors and in staging of malignancy, although contrast-enhanced ultrasonography has shown promise. Cross-sectional imaging with multiplanar reconstruction capability via CT or MRI has become the standard-bearer in the diagnosis, staging and surveillance of renal cancers. The use of specific protocols and the exploitation of different imaging characteristics of RCC subtypes, including variations in contrast agent timing, MRI weighting and digital subtraction, have contributed to this diagnostic capability. Cystic renal masses are a special case, evaluation of which can require multiple imaging modalities. Rigorous evaluation of these lesions can provide information that is crucial to prediction of the likelihood of malignancy. Such imaging is not without risk, however, as radiation from frequent CT imaging has been implicated in the development of secondary malignancies, and contrast agents for CT and MRI can pose risks, particularly in patients with compromised renal function.

Evolving role of magnetic resonance imaging in renal cancer imaging

MRI is an imaging modality that is used in the evaluation and treatment of renal cancer. Although less frequently used than CT, MRI is useful in several aspects of renal cancer evaluation and may have some advantages. MRI has shown promising results for renal cancer staging (especially determination of vascular invasion by tumor), in differentiating malignant from benign complex cystic renal lesions, and in the treatment and follow-up of minimally invasive ablative therapies for renal cancer. In addition, new research shows promise for novel applications of MRI. Herein we review the evolving of MRI in renal cancer imaging.

Radiofrequency ablation of renal tumours: diagnostic accuracy of contrast-enhanced ultrasound for early detection of residual tumour

OBJECTIVE

To evaluate the diagnostic accuracy of contrast-enhanced ultrasound (CEUS) in the early detection of residual tumour after radiofrequency ablation (RFA) of renal tumours.

METHODS

Patients referred to our institution for RFA of renal tumours prospectively underwent CEUS and computed tomography (CT) or magnetic resonance imaging (MRI) before, within 1 day and 6 weeks after treatment. Identification of residual tumour was assessed by three blinded radiologists. Reference standard was CT/MRI performed at least 1 year after RFA.

RESULTS

A total of 66 renal tumours in 43 patients (median age 62 years; range 44-71.5) were studied. Inter-reader agreement (kappa value) was 0.84 for CEUS. Prevalence of residual disease was 19%. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV), respectively, were as follows: 64% [confidence interval (CI) 39-84], 98% [CI 91-100], 82% [CI 52-95] and 92% [CI 83-97] on 24-h CEUS; 79% [CI 52-92], 100% [CI 94-100], 100% [CI 74-100] and 95% [CI 87-100] on 6-week CEUS; 79% [CI 52-92], 95% [CI 86-98], 79% [CI 52-92] and 95% [CI 86-98] on 24-h CT/MRI; and 100% [CI 72-100], 98% [CI 90-100], 91% [CI 62-98] and 100% [CI 93-100] on 6-week CT/MRI.

CONCLUSION

CEUS has high specificity for the early diagnosis of residual tumour after renal RFA.

MR imaging-guided interventions in the genitourinary tract: an evolving concept

MR imaging-guided interventions are well established in routine patient care in many parts of the world. There are many approaches, depending on magnet design and clinical need, based on MR imaging providing excellent inherent tissue contrast without ionizing radiation risk for patients. MR imaging-guided minimally invasive therapeutic procedures have advantages over conventional surgical procedures. In the genitourinary tract, MR imaging guidance has a role in tumor detection, localization, and staging and can provide accurate image guidance for minimally invasive procedures. The advent of molecular and metabolic imaging and use of higher strength magnets likely will improve diagnostic accuracy and allow targeted therapy to maximize disease control and minimize side effects.

RECIST revised: implications for the radiologist. A review article on the modified RECIST guideline

The purpose of this review article is to familiarize radiologists with the recently revised Response Evaluation Criteria in Solid Tumours (RECIST), used in many anticancer drug trials to assess response and progression rate. The most important modifications are: a reduction in the maximum number of target lesions from ten to five, with a maximum of two per organ, with a longest diameter of at least 10 mm; in lymph nodes (LNs) the short axis rather than the long axis should be measured, with normal LN measuring <10 mm, non-target LN ≥10 mm but <15 mm and target LN ≥15 mm; osteolytic lesions with a soft tissue component and cystic tumours may serve as target lesions; an additional requirement for progressive disease (PD) of target lesions is not only a ≥20% increase in the sum of the longest diameter (SLD) from the nadir but also a ≥5 mm absolute increase in the SLD (the other response categories of target lesion are unchanged); PD of non-target lesions can only be applied if the increase in non-target lesions is representative of change in overall tumour burden; detailed imaging guidelines. Alternative response criteria in patients with hepatocellular carcinoma and gastrointestinal stromal tumours are discussed.

Perfusion-CT monitoring of cryo-ablated renal cells tumors

Background

No single and thoroughly validated imaging method in monitoring of cryoablated renal cell carcinoma (RCC) is available. The purpose of our study was to determine the feasibility of dynamic contrast-enhanced perfusion CT (pCT) in evaluating the hemodynamic response of RCC.

Methods

15 patients (14 male, 1 female; age range, 43-81 years; mean age, 62 years) with cryoablated RCC via a transperitoneal approach, underwent to pCT 6-8 months after cryo-therapy. pCT was performed for 65 seconds after intravenous injection of contrast medium (80 mL, 370 mg iodine per millilitre, 4 mL/sec). Perfusion parameters (Time/Density curve; Blood flow, BF; Blood Volume, BV; Mean Transit Time, MTT; Permeability-Surface Area Product, PS) were sampled in the cryoablated tumor area and in ipsilateral renal cortex using deconvolution-based method. A tumor was considered to be not responsive to treatment by CT evidence of pathological contrast enhancement in the cryoablated area or renal mass persistence compared with the preoperative CT control. Written informed consent was obtained from all participants before the study.

Results

After cryotherapy, successfully ablated tumor (n = 13) showed decrease in BV (5,39 +/- 1,28 mL/100 g), BF (69,92 +/- 20,12 mL/100 g/min) and PS (16,66 +/- 5,67 mL/100 g/min) value and increased value of MTT (25,35 +/- 4,3 sec) compared with those of normal renal cortex (BV: 117,86 +/- 31,87 mL/100 g/min; BF: 392,39 +/- 117,32 mL/100 g/min; MTT: 18,02 +/- 3,6 sec; PS: 81,68 +/- 22,75 mL/100 g/min). In one patient, assessment of perfusion parameters was not feasible for breathing artifacts. One tumor showed poor response to treatment by the evidence of nodular contrast enhancement in the region encompassing the original lesion. Two typical enhancement patterns were obtained comparing the Time-Density curves of responsive and not responsive ablated tumors.

Conclusion

Perfusion CT seems to be a feasible and promising technique in monitoring the effects of cryoablation therapy.