Assessment of Local Tumor Progression After Image-Guided Thermal Ablation for Renal Cell Carcinoma

Focal enhancement typically suggests local tumor progression (LTP) after renal cell carcinoma is percutaneously ablated. However, evaluating findings that are false positive or negative of LTP is less familiar to radiologists who have little experience with renal ablation. Various imaging features are encountered during and after thermal ablation. Ablation procedures and previous follow-up imaging should be reviewed before determining if there is LTP. Previous studies have focused on detecting the presence or absence of focal enhancement within the ablation zone. Therefore, various diagnostic pitfalls can be experienced using computed tomography or magnetic resonance imaging examinations. This review aimed to assess how to read images during or after ablation procedures, recognize imaging features of LTP and determine factors that influence LTP.

Safety, efficacy, and mid-term oncological outcomes of computed tomography-guided cryoablation of T1 renal cancer

BACKGROUND

Cryoablation is a promising minimally invasive, nephron-sparing treatment of small renal carcinoma (RCC) in co-morbid patients.

PURPOSE

To assess the safety, efficacy, and cancer-specific outcomes of computed tomography (CT)-guided cryoablation of stage T1 (RCC).

MATERIAL AND METHODS

A retrospective evaluation of 122 consecutive patients with 128 tumors treated with cryoablation during 2016-2017. All patients had biopsy-verified T1 RCC.

RESULTS

Median age was 69 years (IQR=59-76); 69% were male. Median tumor size was 26 mm (± 20-33); 9% were stage T1b. Mean follow-up time was 36.3±12.0 months. In total, 14 (11%) procedures led to complications, of which 4 (3%) were intraoperative, 5 (4%) appeared ≤30 days and 5 (4%) >30 days after treatment. Major complications arose after 4 (3%) procedures. Statistically significant associations were found between major complications and stage T1b (P = 0.039), RENAL score (P = 0.010), and number of needles used in cryoablation (P = 0.004). Residual tumor was detected after 4 (3%) procedures and 5 (4%) tumors had local tumor progression. Of 122 patients, 3 (2%) advanced to metastatic disease. Significant statistical associations were found between local tumor progression and T1b stage tumors and number of needles used in cryoablation (P = 0.05 and P = 0.004, respectively). For patients with T1a tumors, the one- and three-year disease-free survival was 98% and 95%, respectively, and for T1b 100% after one year and 75% after three years.

CONCLUSIONS

This study showed that cryoablation is a safe and effective treatment of stage T1 RCC and suggests that in selecting candidates for cryoablation of RCC, the tumor characteristics are more critical than patients' baseline health status.

Cryptococcus granuloma mimicking local progressed tumor after cryoablation of renal cell carcinoma: A case report

Infectious granulomas arising in the kidney are rare. However, there are few reports regarding renal granulomas, such as xanthogranulomatous pyelonephritis, sarcoidosis, malakoplakia, and tuberculosis. Here, we report a case of cryptococcal granuloma resembling a locally progressed tumor after percutaneous cryotherapy for renal cell carcinoma. A male patient in his 80s with rheumatoid arthritis underwent computed tomography (CT)-guided cryoablation for biopsy-proven papillary renal cell carcinoma. Follow-up contrast-enhanced CT imaging obtained 4 months after ablation confirmed an enhanced mass on the edge of the ablation zone. There were no symptoms related to the mass. This mass was radiologically diagnosed as local tumor progression and treated with repeated cryoablation. Percutaneous biopsy of the mass was performed immediately after the second cryoablation, and the mass was pathologically diagnosed as granuloma related to Cryptococcus infection. The patient was administered antifungal fluconazole for 1 year with a good outcome.

Split-bolus CT urography after microwave ablation of renal cell carcinoma improves image quality and reduces radiation exposure

OBJECTIVE

To compare image quality and radiation dose between single-bolus 2-phase and split-bolus 1-phase CT Urography (CTU) performed immediately after microwave ablation (MWA) of clinically localized T1 (cT1) RCC.

METHODS

Forty-two consecutive patients (30 M, mean age 67.5 ± 9.0) with cT1 RCC were treated with MWA from 7/2013 to 12/2013 at two academic quaternary-care institutions. Renal parenchymal enhancement, collecting system opacification and distention and size-specific dose estimate (SSDE) were quantified and image quality subjectively assessed on single-bolus 2-phase versus split-bolus 1-phase CTU. Kruskal-Wallis and Pearson's Chi-squared tests were performed to assess differences in continuous and categorical variables, respectively. Two-sample T test with equal variances was used to determine differences in quantitative and qualitative image data.

RESULTS

Median tumor diameter was larger [2.9 cm (IQR 1.7-5.3) vs 3.6 cm (IQR 1.7-5.7), p = 0.01] in the split-bolus cohort. Mean abdominal girth (p = 0.20) was similar. Number of antennas used and unenhanced CTs obtained before and during MWA were similar (p = 0.11-0.32). Renal pelvis opacification (2.5 vs 3.5, p < 0.001) and distention (4 mm vs 8 mm, p < 0.001) were improved and renal enhancement (Right: 127 HU vs 177 HU, p = 0.001; Left: 124 HU vs 185 HU, p < 0.001) was higher for the split-bolus CTU. Image quality was superior for split-bolus CTU (3.2 vs 4.0, p = 0.004). Mean SSDE for the split-bolus CTU was significantly lower [163.9 mGy (SD ± 73.9) vs 36.3 mGy (SD ± 7.7), p < 0.001].

CONCLUSION

Split-bolus CTU immediately after MWA of cT1 RCC offers higher image quality, improved opacification/distention of the collecting system and renal parenchymal enhancement at a lower radiation dose.

ACR Appropriateness Criteria® Post-Treatment Follow-up and Active Surveillance of Clinically Localized Renal Cell Carcinoma: 2021 Update

Renal cell carcinoma (RCC) accounts for most malignant renal tumors and is considered the most lethal of all urologic cancers. For follow-up of patients with treated or untreated RCC and those with neoplasms suspected to represent RCC, radiologic imaging is the most valuable component of surveillance, as most relapses and cases of disease progression are identified when patients are asymptomatic. Understanding the strengths and limitations of the various imaging modalities for the detection of disease, recurrence, or progression is essential when planning follow-up regimens. This document addresses the appropriate imaging examinations for asymptomatic patients who have been treated for RCC with radical or partial nephrectomy or ablative therapies. It also discusses the appropriate imaging examinations for asymptomatic patients with localized biopsy-proven or suspected RCC undergoing active surveillance. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer-reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

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.

Cross-sectional imaging assessment of renal masses with emphasis on MRI

Magnetic resonance imaging (MRI) is a useful complementary imaging tool for the diagnosis and characterization of renal masses, as it provides both morphologic and functional information. A core MRI protocol for renal imaging should include a T1-weighted sequence with in- and opposed-phase images (or, alternatively with DIXON technique), T2-weighted and diffusion-weighted images as well as a dynamic contrast-enhanced sequence with subtraction images, followed by a delayed post-contrast T1-weighted sequence. The main advantages of MRI over computed tomography include increased sensitivity for contrast enhancement, less sensitivity for detection of calcifications, absence of pseudoenhancement, and lack of radiation exposure. MRI may be applied for renal cystic lesion characterization, differentiation of renal cell carcinoma (RCC) from benign solid renal tumors, RCC histologic grading, staging, post-treatment follow-up, and active surveillance of patients with treated or untreated RCC.

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.

Contrast-enhanced ultrasound after successful cryoablation of benign and malignant renal tumours: how long does tumour enhancement persist?

INTRODUCTION

To investigate how long successfully ablated tumours take to become completely avascular at CEUS after cryoablation.

METHODS

Ninety-five patients had percutaneous cryoablation of 103 renal tumours investigated at CEUS on post-operative day one. If the lesion was avascular, a contrast-CT/MR was scheduled six months after the procedure, while CEUS was repeated if the lesion still displayed enhancement, until the disappearance of intralesional vascularity. Technical success was defined when the tumour was covered completely by the ablation zone. Technique efficacy was assessed at six months of follow-up.

RESULTS

Technical efficacy was obtained for 101/103 cryoablations, 56% of which (57/101) were avascular on post-operative day one. After one week, two weeks, one month 83%, 91% and 100% of these 101 lesions, respectively, were avascular. Two tumours were unsuccessfully treated. They displayed persistent intralesional vascularity at CEUS one month after the procedure.

CONCLUSIONS

After cryoablation, obtaining CEUS before one month may be misleading. When technical efficacy is obtained, disappearance of intralesional enhancement is observed within two weeks in the majority of cases (91%), but can persist until one month. Identification of tumour enhancement after one month may be concerning for residual viable tumour.

Mimics and Pitfalls in Renal Imaging

There are several potential pitfalls that radiologists face when interpreting images of the kidneys. Some result from image acquisition and can arise from the imaging equipment or imaging technique, whereas others are patient related. Another category of pitfalls relates to image interpretation. Some difficulties stem from methods to detect enhancement after contrast administration, whereas others are benign entities that can mimic a renal tumor. Finally, interpretation and diagnosis of fat-containing renal masses may be tricky due to the complexities discerning the pattern of fat within a mass and how that translates to an accurate diagnosis.

Cryoablation: A promising non-operative therapy for low-risk breast cancer

BACKGROUND

The aim of this study was to evaluate the feasibility of cryoablation for early-stage low-risk breast cancer without tumor resection.

METHODS

Women diagnosed with ER+, PR+, and HER2-infiltrating ductal carcinomas ≤1.5 cm were treated with cryoablation. The non-surgical procedure used a Visica® 2 Treatment System with ultrasound guidance for ablation of the tumor with a 1 cm margin. Patients were monitored at 6-month intervals by MRI, mammogram, and ultrasound.

RESULTS

Twelve patients with unifocal breast cancer were treated with cryoablation for local control without follow-up tumor resection. All patients received adjuvant endocrine therapy, and none had radiation. The median follow-up was 28.5 (range = 4-41) months with 11 patients having at least one six-month follow-up. All imaging modalities showed complete ablation of target zone 11/11 (100%). Four patients (33.3%) have been followed up for ≥ 2 years with no local failure or residual disease.

CONCLUSION

Cryoablation of early-stage low-risk (ER+, PR+, and HER2-) breast cancer is a safe alternative to surgery.

Percutaneous Image-guided Thermal Ablation for Renal Cell Carcinoma

Nephrectomy is the gold standard for the treatment of renal cell carcinoma (RCC). However, some patients are not suitable candidates for nephrectomy because of high surgical risk, reduced renal function, or the presence of multiple renal tumors. Percutaneous image-guided thermal ablation, including cryoablation and radiofrequency ablation, is a minimally invasive and highly effective treatment and can be used to treat RCC in patients who are not good candidates for surgery. This article will review percutaneous image-guided thermal ablation for RCC, covering treatment indications, ablation modalities and techniques, oncologic outcomes, and possible complications. In addition, the characteristics of each ablation modality and its comparison with nephrectomy are also presented.

MRI Findings After Cryoablation of Primary Breast Cancer Without Surgical Resection

RATIONALE AND OBJECTIVES

To retrospectively evaluate findings on serial magnetic resonance imaging (MRI) after cryoablation for breast cancer lesions without subsequent surgical resection.

MATERIALS AND METHODS

This study was approved by the Institutional Review Board and the requirement to obtain informed consent waived. Ductal carcinoma in situ or invasive carcinoma ≤15 mm, nuclear grade 1 or 2, estrogen receptor positive/human epidermal growth factor 2 negative without lymph node metastasis were treated with cryoablation without subsequent excision. Two observers independently reviewed the first two postcryoablation MRIs for shape (none, focus-to-mass, or nonmass enhancement) and suspicion of residual disease (positive or negative). Fisher's exact or the Mann-Whitney U test was used to assess significance. Interobserver agreement on findings was evaluated by calculating κ values.

RESULTS

Fifty-four patients were enrolled. The first and second postcryoablation MRIs were performed 22-171 days and 82-487 days after cryoablation, respectively. Interobserver agreement ranged from fair to moderate (κ = 0.356-0.434). Observer 1 or 2 identified suspicious areas on the first postcryoablation MRI in seven cases (13.0%). These were significantly associated with focus-to-mass shape (vs non-focus-to-mass: nonmass enhancement or none) and residual disease or recurrence suspected by both observers (p < 0.001). There were no cases of both observers identifying suspicious findings on the second postcryoablation MRI.

CONCLUSION

Suspicious findings can be detected within the treated area at the first postcryoablation MRI. These can resolve during subsequent adjuvant therapies and follow-up.

Bioluminescence Image as a Quantitative Imaging Biomarker for Preclinical Evaluation of Cryoablation in a Murine Model

PURPOSE

To employ bioluminescence imaging (BLI) as a quantitative imaging biomarker to assess preclinical evaluation of cryoablation in a murine model.

MATERIALS AND METHODS

In vitro, Colon26-Luc (C26-Luc) cells were seeded at 6 different concentrations in 35-mm dishes. These were divided into 6 groups: group 0 (G0), a control group without treatment; and groups 1-5 (G1-G5) according to the number of freeze-thaw cycles, with each cycle consisting of freezing at -80°C for 10 min followed by thawing at room temperature for 5 minutes. BLI and flow-cytometric analysis were performed after cryotherapy. In vivo, 20 tumor-bearing mice with C26-Luc cells were divided into 4 groups: group 0 (G0), a control group; and groups 1-3 (G1-G3) according to the number of freeze-thaw cycles. Each cryoablation procedure was performed for 30 seconds with liquid nitrogen (-170°C) applied with cotton-tipped applicators. BLI was acquired at 6 hours and 1, 3, and 7 days after treatments.

RESULTS

In vitro, BLI signal showed a negative correlation with the number of freeze-thaw cycles (r = -0.86, P = .02). In vivo, there was no difference in tumor volume at 1 day after cryoablation among all groups, but the BLI signals were significantly different between G0 and G2/G3 (P = .03 and P = .02, respectively) and between G1 and G3 (P = .04). BLI signals reflected tumor growth speed and survival ratio.

CONCLUSIONS

This study demonstrates the direct validation of BLI as a quantitative tool for the early assessment of therapeutic effects of cryoablation.

Cryotherapy of Renal Lesions: Enhancement on Contrast-Enhanced Sonography on Postoperative Day 1 Does Not Imply Viable Tissue Persistence

OBJECTIVES

To investigate whether persistent enhancement detected on contrast-enhanced sonography at postoperative day 1 (early contrast-enhanced sonography) after cryoablation of renal tumors implies the presence of residual viable tumor tissue, defined as residual enhancing tissue on reference imaging (computed tomography or magnetic resonance imaging) performed 6 months after the procedure.

METHODS

Seventy-four patients with percutaneous cryoablation of renal tumors had early contrast-enhanced sonography from November 2011 to August 2015. Two independent readers evaluated early contrast-enhanced sonographic findings and contrast-enhanced sonographic investigations performed 1 month after cryoablation of lesions that displayed enhancement on early contrast-enhanced sonography. They scored intralesional enhancement in 4 groups: no enhancement, few intralesional vessels, focal enhancing areas, and diffuse enhancement. Inter-reader agreement in evaluating lesion vascularity on early contrast-enhanced sonography was assessed with weighted κ statistics. Computed tomography or magnetic resonance imaging performed 6 months after the treatment was the reference procedure for assessing the absence or presence of residual disease.

RESULTS

Inter-reader agreement in assessing intratumoral vascularization on early contrast-enhanced sonography was very good (κ = 0.90). Enhancement was absent for both readers in 33 of 74 cases; only a few intralesional vessels were visible in 21; whereas diffuse or focal enhancement was present in 13. In the remaining 7 patients, there were differences. Four lesions with focal enhancement on early contrast-enhanced sonography and 1 that was considered avascular had residual tumors on reference imaging. Ablation was successful in the remaining 69 of 74 patients (93%).

CONCLUSIONS

After cryoablation, intratumoral enhancement on early contrast-enhanced sonography does not imply tumor cell viability.

Percutaneous image-guided cryoablation: current applications and results in the oncologic field

Percutaneous imaging-guided cryoablation (PICA) is a recently developed technique, which applies extreme hypothermia to destroy tumours under close imaging surveillance. It is minimally invasive, safe, repeatable, and does not interrupt or compromise other oncologic therapies. It presents several advantages over more established heat-based thermal ablation techniques (e.g. radiofrequency ablation; RFA) including intrinsic analgesic properties, superior monitoring capability on multi-modal imaging, ability to treat larger tumours, and preservation of tissue collagenous architecture. There has been a recent large increase in reports evaluating the utility of PICA in a wide range of patients and tumours, but systematic analysis of the literature is challenging due to the rapid pace of change and predominance of extensively heterogeneous level III studies. The precise onco-therapeutic role of PICA has not been established. This narrative review outlines the available evidence for PICA in a range of tumours. Current indications include curative therapy of small T1a renal tumours; curative/palliative therapy of small primary/secondary lung tumours where RFA is unsuitable; palliation of painful bone metastases; and urologic treatment of organ-confined prostate cancer. There is growing evidence to support its use for small hepatic tumours, and encouraging results have been obtained for breast tumours, extra-abdominal desmoid tumours, and management of higher-stage tumours and oligometastatic disease. However, the overall evidence base is weak, effectively restricting PICA to cases where standard therapy and RFA are unsuitable. As the technique and evidence continue to mature, the benefits of this emerging technique will hopefully become more widely available to cancer patients in the future.