Active surveillance of small renal masses

Multicenter study of active surveillance for small renal masses: Real world practice pattern

INTRODUCTION

Active surveillance (AS) is a safe strategy for small renal masses (SRM) suspicious of renal cell carcinoma. In this study we analyze real world outcomes of active surveillance SRM from 5 tertiary Spanish centers, assessing clinical, radiological, and pathological characteristics, as well as therapeutic options.

METHODS

A multicenter retrospective review was conducted including patients on AS from January 2012 to September 2024. We analyzed the indication for AS, initial lesion size, growth rate (GR), and progression on active surveillance. Cox regression analysis was performed to identify predictor of deferred intervention (DI).

RESULTS

A total of 384 patients with renal tumors were included in AS, with an initial mean tumor size of 20.5mm. With a mean follow-up period of 43 months, the average GR across the cohort was 1.4 mm/y. About 15% of patients (n = 59) received active treatment (partial nephrectomy 56%, radical nephrectomy 16%, and radiofrequency 28%). Age, tumor size and tumor growth were factors correlated with delayed intervention, and only initial tumor size was correlated with GR. Pathological analysis after active treatment showed high grade clear cell carcinoma in 43.5% of cases with a GR of > 5 mm/y, as compared to 19.4% of oncocytomas in slow growing lesions. No disease progression nor cancer-specific deaths were observed in our series.

CONCLUSIONS

In our multicenter cohort, AS is a valid option for SRMs without affecting oncological outcomes, with clinical factors such as age, tumor size, GR and initial biopsy influencing decisions on intervention.

Bispecific antibodies as powerful immunotherapeutic agents for urological cancers: Recent innovations based on preclinical and clinical evidence

Conventional immunotherapy has emerged as a key option for cancer treatment. However, its efficacy has been limited in urological cancers, especially prostate cancer, because of the immunosuppressive tumor microenvironment (TME), difficulty in drug delivery, aberrant immune response, and damage to normal cells. Bispecific antibodies (BsAbs) are engineered proteins with two different antigen-binding domains, designed using different technologies and in various formats. BsAb-based tumor immunotherapy has yielded optimistic results in preclinical and clinical investigations of many tumor types, including urological cancers. However, a series of challenges, including tumor heterogeneity, TME, Ab immunogenicity, adverse effects, serum half-life, low response rates, and drug resistance, hamper the application of BsAbs. In this review, we provide insights into the most common BsAb platforms with different mechanisms of action, which are under preclinical and clinical research, along with ways to overcome the challenges in BsAb administration for treating urological cancer.

Diagnostic Value of Clear Cell Likelihood Score v1.0 and v2.0 for Common Subtypes of Small Renal Masses: A Multicenter Comparative Study

BACKGROUND

Clear cell likelihood score (ccLS) is reliable for diagnosing small renal masses (SRMs). However, the diagnostic value of Clear cell likelihood score version 1.0 (ccLS v1.0) and v2.0 for common subtypes of SRMs might be a potential score extension.

PURPOSE

To compare the diagnostic performance and interobserver agreement of ccLS v1.0 and v2.0 for characterizing five common subtypes of SRMs.

STUDY TYPE

Retrospective.

POPULATION

797 patients (563 males, 234 females; mean age, 53 ± 12 years) with 867 histologically proven renal masses.

FIELD STRENGTH/SEQUENCES

3.0 and 1.5 T/T2 weighted imaging, T1 weighted imaging, diffusion-weighted imaging, a dual-echo chemical shift (in- and opposed-phase) T1 weighted imaging, multiphase dynamic contrast-enhanced imaging.

ASSESSMENT

Six abdominal radiologists were trained in the ccLS algorithm and independently scored each SRM using ccLS v1.0 and v2.0, respectively. All SRMs had definite pathological results. The pooled area under curve (AUC), accuracy, sensitivity, and specificity were calculated to evaluate the diagnostic performance of ccLS v1.0 and v2.0 for characterizing common subtypes of SRMs. The average κ values were calculated to evaluate the interobserver agreement of the two scoring versions.

STATISTICAL TESTS

Random-effects logistic regression; Receiver operating characteristic analysis; DeLong test; Weighted Kappa test; Z test. The statistical significance level was P < 0.05.

RESULTS

The pooled AUCs of clear cell likelihood score version 2.0 (ccLS v2.0) were statistically superior to those of ccLS v1.0 for diagnosing clear cell renal cell carcinoma (ccRCC) (0.907 vs. 0.851), papillary renal cell carcinoma (pRCC) (0.926 vs. 0.888), renal oncocytoma (RO) (0.745 vs. 0.679), and angiomyolipoma without visible fat (AMLwvf) (0.826 vs. 0.766). Interobserver agreement for SRMs between ccLS v1.0 and v2.0 is comparable and was not statistically significant (P = 0.993).

CONCLUSION

The diagnostic performance of ccLS v2.0 surpasses that of ccLS v1.0 for characterizing ccRCC, pRCC, RO, and AMLwvf. Especially, the standardized algorithm has optimal performance for ccRCC and pRCC. ccLS has potential as a supportive clinical tool.

EVIDENCE LEVEL

4.

TECHNICAL EFFICACY

Stage 2.

Clinical value of contrast-enhanced ultrasound combined with quantitative analysis in Bosniak ≥ II cystic renal masses

OBJECTIVE

The 2019 Bosniak classification has improved the precise and detailed quantitative evaluation criteria, making the diagnosis of cystic renal masses (CRMs) more accurate and objective. This study addresses the clinical value of quantitative analysis and aims to investigate the feasibility of combining contrast-enhanced ultrasound (CEUS) with quantitative analysis for diagnosing Bosniak ≥ II CRMs.

METHODS

We retrospectively obtained 58 CRMs with confirmed pathology, which underwent CEUS and Contrast-enhanced computer tomography (CECT) evaluations according to Bosniak classification between January 2013 and August 2024. These lesions were divided into benign and malignant groups, followed by a quantitative analysis of the morphological details detected by CEUS. All morphological parameters were compared, and the diagnostic efficiencies were evaluated using receiver operating characteristics (ROC) curves, logistic regression (LR) analysis, and diagnostic curve analysis (DCA). Additionally, a cohort of 72 lesions was monitored for a period of ≥ 3 years, and changes in Bosniak classification were analyzed by categorizing them into stable, upgraded, and downgraded categories.

RESULTS

The analysis revealed no statistically significant difference between CEUS and CECT in our cohort's malignancy predictive rates across different Bosniak grades (p = 0.640). All morphological quantitative parameters showed statistically significant differences between the two groups (p < 0.001). ROC curve analysis revealed that the sum of enhanced wall thickness and enhanced septum thickness among quantitative parameters had the highest AUC value (AUC: 0.9226). Both LR models demonstrated superior clinical diagnostic performance with similar level of accuracy between qualitative and quantitative analysis, as evidenced by ROC (AUC: 0.9470, 0.9619, respectively) and DCA analyses. None of the lesions in the follow-up cohort were upgraded, suggesting that CRMs are relatively stable tumors with a low malignant potential.

CONCLUSION

This retrospective study demonstrated that CEUS combined with Bosniak classification and quantitative analysis could enhance diagnostic confidence in differentiating Bosniak ≥ II CRMs and could serve as a viable alternative to CECT in specific cases.

Propensity score-matched analysis comparing robot-assisted partial nephrectomy and image-guided percutaneous cryoablation for cT1 renal cell carcinoma

OBJECTIVES

This study aimed to compare the clinical outcomes of robot-assisted partial nephrectomy (RAPN) and image-guided percutaneous cryoablation (IG-PCA) for clinical T1 renal cell carcinoma.

MATERIALS AND METHODS

We conducted a retrospective analysis of 679 patients with clinical T1 renal cell carcinoma treated with RAPN or IG-PCA between 2012 and 2021. Propensity scores were calculated via logistic analysis to adjust for imbalances in baseline characteristics. We compared oncological and functional outcomes between the 2 treatment groups.

RESULTS

Following the matching process, 108 patients were included in each group. No patient in the RAPN group developed local recurrence. In the IG-PCA group, three patients experienced local tumor progression. The patients underwent salvage thermal ablations by the secondary technique; 2 underwent IG-PCA and 1 underwent microwave ablation, resulting in a local control rate of 100%. The Kaplan-Meier analysis showed no statistically significant differences between the groups in terms of 5-year recurrence-free survival, metastasis-free survival, and overall survival (log-rank test; P = 0.11, P = 0.64, and P = 0.17, respectively). No significant differences were observed in the 2 treatments in major and overall complication rates (P = 0.75 and P = 0.82, respectively). Both groups showed similar rates of less than 10% estimated glomerular filtration rate decline at 12 months post-treatment and 5-year renal function preservation rates (P = 0.88 and P = 0.38, respectively).

CONCLUSIONS

IG-PCA demonstrated oncological outcomes comparable to those of RAPN. RAPN addressed the disadvantages of conventional procedures and allowed for safety outcomes comparable to IG-PCA.

[Small renal mass: which criteria are decisive for a tumor board?]

Small renal masses (SRM) are a heterogeneous group of tumors with varying metastatic potential. The increasing use and improvement in the quality of abdominal imaging have led to an increasingly earlier diagnosis of incidental SRM, which are asymptomatic and confined to the organ. Despite these advances in imaging and the growing use of renal tumor biopsies, preoperative diagnosis of malignancy remains difficult. The treatment of SRM has shifted away from radical nephrectomy and now primarily includes organ-sparing surgery or active surveillance. The optimal strategy for treating SRM is continuously evolving as studies from prospective data registries can identify factors that influence both short- and long-term patient outcomes. Recent research on biomarkers, imaging techniques, and machine learning offer promising approaches to a deeper understanding of tumor biology and treatment options for this patient population.

Diagnostic Value of Contrast-Enhanced Ultrasound in Differentiating Malignant from Benign Small Renal Masses After CT/MRI

Background: The aim of this study was to assess the diagnostic performance of contrast-enhanced ultrasound (CEUS) in characterizing small renal masses (SRMs) measuring less than 3 cm and in distinguishing between malignant and benign SRMs. Methods: A retrospective study was conducted between January 2022 and January 2023 at the Radiology Department of (Anonymized data), with a total of 43 patients assessed via CT and MRI scans, which were subsequently studied by experienced radiologists who were blinded to the pathology results. The CEUS findings were then compared with histopathological examination outcomes or follow-up imaging results. Results: The study results revealed a notably high level of diagnostic accuracy, with sensitivity at 0.875, specificity at 0.94, positive predictive value at 0.95, and negative predictive value at 0.86 for characterizing SRMs. Spearman rank correlation analysis substantiated a robust positive linear correlation between the CEUS findings and biopsy results (r = 0.972). Conclusions: These findings underscore the potential utility of CEUS as a valuable tool for discriminating between malignant and benign SRMs, carrying significant implications for clinical decision-making and leading to improved patient outcomes. However, larger validation studies are imperative to establish its role in routine clinical practice and to address potential limitations.

Renal Oncocytoma: A Systematic Review of Its Metastatic Features

Oncocytomas are referred to as benign kidney neoplasms. They primarily affect adults, with patients over 70 years old being the most affected. Renal oncocytomas (ROs) are frequently detected by excision, biopsy, or scan. Hematuria, flank pain, and a palpable mass are the traditional trio of symptoms. Oncocytomas appear as well-circumscribed, tan or mahogany-coloured masses with a central scar that is stellate. Histological features include well-circumscribed lesions, bland cytology, eosinophilic cytoplasm, regular nuclei with prominent central nucleoli, and nested architecture. ROs are rarely linked to an aggressive clinical course and have an excellent prognosis. There is proof that the disease can spread to the liver and bones. Some literature has also reported oncocytoma metastases to the lung and liver. This systematic review of the literature examines and evaluates the malignant potential of oncocytoma. The purpose of the study was to determine whether ROs can be diagnosed as a benign condition or if malignancy needs to be considered and investigated. Seventeen studies were analysed which had a total of 412 ROs. Four patients (one percent) died as a result of their illness. There was evidence of disease progression in every patient who passed away from their illness. Six patients (1.5%) experienced disease progression in total. Three hundred and seventeen patients (80%) underwent radical nephrectomy, while 81 patients (20%) underwent partial nephrectomy. Liver, bone, lung, lymphadenopathy, and local recurrence were among the metastasis sites. Perinephric fat invasion, renal sinus fat invasion, renal capsular invasion, and vascular invasion are characteristics of metastatic behavior that have been found. Despite this, the small number of patients who experienced disease progression and/or death as a result of ROs implies that aggressive malignant behavior is not always correlated with the presence of metastatic features or disease. Oncocytomas should be viewed as having a low potential for malignancy rather than as benign. Individuals who exhibit aggressive characteristics, such as vascular invasion and/or perinephric fat invasion, have an atypically good prognosis. Despite advancements in imaging and immunochemical techniques, it is indisputable that ROs, which were first classified as renal tumours in 1976, continue to pose a diagnostic challenge for multidisciplinary teams. There is considerable variation in practice across the globe due to difficulties in confirming ROs, especially when it comes to metastatic disease. There is even more variation in the management of follow-up care that follows. This will remain the MDT's current state until randomised controlled trials, long-term results, and a better comprehension of the behavior of this tumour are obtained.

Scientific Status Quo of Small Renal Lesions: Diagnostic Assessment and Radiomics

Background: Small renal masses (SRMs) are defined as contrast-enhanced renal lesions less than or equal to 4 cm in maximal diameter, which can be compatible with stage T1a renal cell carcinomas (RCCs). Currently, 50-61% of all renal tumors are found incidentally. Methods: The characteristics of the lesion influence the choice of the type of management, which include several methods SRM of management, including nephrectomy, partial nephrectomy, ablation, observation, and also stereotactic body radiotherapy. Typical imaging methods available for differentiating benign from malignant renal lesions include ultrasound (US), contrast-enhanced ultrasound (CEUS), computed tomography (CT), and magnetic resonance imaging (MRI). Results: Although ultrasound is the first imaging technique used to detect small renal lesions, it has several limitations. CT is the main and most widely used imaging technique for SRM characterization. The main advantages of MRI compared to CT are the better contrast resolution and tissue characterization, the use of functional imaging sequences, the possibility of performing the examination in patients allergic to iodine-containing contrast medium, and the absence of exposure to ionizing radiation. For a correct evaluation during imaging follow-up, it is necessary to use a reliable method for the assessment of renal lesions, represented by the Bosniak classification system. This classification was initially developed based on contrast-enhanced CT imaging findings, and the 2019 revision proposed the inclusion of MRI features; however, the latest classification has not yet received widespread validation. Conclusions: The use of radiomics in the evaluation of renal masses is an emerging and increasingly central field with several applications such as characterizing renal masses, distinguishing RCC subtypes, monitoring response to targeted therapeutic agents, and prognosis in a metastatic context.

Clinical Evaluation of Cystic Renal Masses With Bosniak Classification by Contrast-Enhanced Ultrasound and Contrast-Enhanced Computer Tomography

OBJECTIVES

The study aims to compare retrospectively three clinically applied methods for the diagnostic performance of cystic renal masses (CRMs) by contrast-enhanced ultrasound (CEUS) and contrast-enhanced computer tomography (CECT) with Bosniak classification system.

METHODS

A total of 52 cases of Bosniak II-IV CRMs in 49 consecutive patients were diagnosed from January 2013 to July 2022 and their data were analyzed. All patients had been subjected to CEUS and CECT simultaneously. Pathological diagnoses and masses stability were used as standard references to determine whether lesions were malignant or benign. Then 49 CRMs only with pathologic results were classified into group 1 and 2.

RESULTS

A total of 52 CRMs in 49 enrolled patients were classified into 8 category II, 16 category IIF, 15 category III, and 13 category IV by CEUS (EFSUMB 2020), 10 category II, 13 category IIF, 16 category III, and 13 category IV by CEUS (V2019), while 15 category II, 9 category IIF, 13 category III, and 15 category IV by CECT (V2019). Pathological results and masses stability longer than 5 years follow-up performed substantially for CEUS (EFSUMB 2020), CEUS (V2019), and CECT (V2019) (kappa values were 0.696, 0.735, and 0.696, respectively). Among 49 pathologic approving CRMs, wall/septation thickness ≥4 mm, wall/septation thickness, presence of enhancing nodule and the diameter were found to be statistically significant for malignancy. Twenty-two malignant masses were correctly diagnosed by CEUS (V2019), while 21 malignant masses were both correctly diagnosed by CEUS (EFSUMB 2020) and CECT (V2019), and 1 mass was misdiagnosed.

CONCLUSIONS

Bosniak classification of EFSUMB 2020 version might be as accurate as version 2019 CEUS and version 2019 CECT in diagnosing CRMs, and CEUS is found to have an excellent safety profile in dealing with clinical works.

Impact of diabetes and chronic kidney disease on active surveillance outcomes for small renal masses: A cohort study

Introduction

The American Cancer Society estimates 79,000 individuals will be diagnosed with kidney cancer in 2022, most of which are initially found as small renal masses (SRMs). Proper management of SRM patients includes careful evaluation of risk factors such as medical comorbidities and renal function. To investigate the importance of these risk factors, we examined their effect on crossover to delayed intervention (DI) and overall survival (OS) in patients undergoing active surveillance (AS) for SRMs.

Methods

This is an Institutional Review Board-approved retrospective analysis of AS patients presented at kidney tumor conferences with SRMs between 2007 and 2017. Univariable and multivariable logistic regression analyses were performed to determine how factors including estimated glomerular filtration rate (eGFR), diabetes, and chronic kidney disease are associated with DI and OS.

Results

A total of 111 cases were reviewed. In general, AS patients were elderly and had significant comorbidities. On univariate analysis, intervention was more likely to occur in patients with a younger age (P = 0.01), better kidney function (P = 0.01), and higher tumor growth rates (GRs) (P = 0.02). Higher eGFR was associated with better survival (P = 0.03), while higher tumor GRs (P = 0.014), greater Charlson Comorbidity Index (P = 0.01), and larger tumors (P = 0.01) were associated with worse OS. Of the comorbidities, diabetes was found to be an independent predictor of worse OS (P = 0.01).

Conclusions

Patient-level factors - such as diabetes and eGFR - are associated with the rate of DI and OS among SRM patients. Consideration of these factors may facilitate better AS protocols and improve patient outcomes for those with SRMs.

Growth Kinetics of Pancreatic Neuroendocrine Neoplasms by Histopathologic Grade

OBJECTIVES

The aims of the study are to describe the growth kinetics of pathologically proven, treatment-naive pancreatic neuroendocrine neoplasms (panNENs) at imaging surveillance and to determine their association with histopathologic grade and Ki-67.

METHODS

This study included 100 panNENs from 95 patients who received pancreas protocol computed tomography or magnetic resonance imaging from January 2005 to July 2022. All masses were treatment-naive, had histopathologic correlation, and were imaged with at least 2 computed tomography or magnetic resonance imaging at least 90 days apart. Growth kinetics was assessed using linear and specific growth rate, stratified by grade and Ki-67. Masses were also assessed qualitatively to determine other possible imaging predictors of grade.

RESULTS

There were 76 grade 1 masses, 17 grade 2 masses, and 7 grade 3 masses. Median (interquartile range) linear growth rates were 0.06 cm/y (0-0.20), 0.40 cm/y (0.22-1.06), and 2.70 cm/y (0.41-3.89) for grade 1, 2, and 3 masses, respectively (P < 0.001). Linear growth rate correlated with Ki-67 with r2 of 0.623 (P < 0.001). At multivariate analyses, linear growth rate was the only imaging feature significantly associated with grade (P = 0.009).

CONCLUSIONS

Growth kinetics correlate with Ki-67 and grade. Grade 1 panNENs grow slowly versus grade 2-3 panNENs.

Downstaging and Pathological Complete Response of Locally Recurrent Sarcomatoid Renal Cell Carcinoma under Pembrolizumab and Lenvatinib: A Case Report and Review of Literature

The advent of immune checkpoint inhibition opened new perspectives for patients with recurrent or metastasized renal cell carcinoma. In case of recurrent disease, surgical resection remains the most promising therapeutic option. Surgical resection is associated with improved overall survival and demonstrated curative potential given complete resection of metastases can be performed. This report presents the case of a patient with local recurrence of dedifferentiated sarcomatoid renal cell carcinoma approximately 1 year after initial open lumbar nephrectomy. After initial evaluation, surgical removal was deemed infeasible and an induction therapy with pembrolizumab and lenvatinib was initiated. After 3 months, corresponding to 5 cycles of pembrolizumab, the tumor showed a partial response on imaging control and was successfully resected en bloc. Histopathological examination of the specimen revealed no evidence of viable neoplastic cells. This is the first report describing a complete pathological response of a locally recurrent dedifferentiated sarcomatoid renal cell carcinoma after treatment with pembrolizumab and lenvatinib. Overall, the combination therapy was well tolerated with a maximum Common Terminology Criteria for Adverse Events Level of Two. These findings underline the potential of multimodal therapeutic strategies for recurrent renal cell carcinoma, such as induction therapies to downstage initially nonresectable masses, and highlight the need for prospective studies to allow for evidence-based treatment plans.

Cost-effectiveness of Contrast-Enhanced Ultrasound for Diagnosis and Active Surveillance of Complex Cystic Renal Lesions

Purpose

To determine the cost-effectiveness of Contrast-Enhanced Ultrasound (ceUS) for the active surveillance of complex renal masses compared to the more established imaging modalities of CT and MRI.

Methods

A decision-analytic Markov state microsimulation model was constructed in TreeAge Pro. We simulated independent cohorts of 100,000 60-year-old individuals with either a Bosniak IIF or Bosniak III complex renal mass who were followed for 10 years or until death. The model compared three imaging strategies: (1) ceUS, (2) contrast-enhanced magnetic-resonance imaging (ceMRI), and (3) contrast-enhanced computed tomography (ceCT) for active surveillance of a complex renal mass.

Results

For 60-year-old patients with either Bosniak IIF or III renal masses, ceUS was the most cost-effective strategy even after varying rates of active surveillance from 10-100%.

Conclusion

ceUS is a viable and cost-effective option in the active surveillance of Bosniak class IIF and III renal cysts. Even after varying the rates of active surveillance usage, ceUS was robust and remained the most dominant strategy. For patients who have impaired kidney functions, ceUS is can be a safer alternative than non-contrast enhanced CT or MRI in the management of patients with Bosniak III renal cysts.

Urine Molecular Biomarkers for Detection and Follow-Up of Small Renal Masses

Active surveillance (AS) is the best strategy for small renal masses (SRMs) management; however, reliable methods for early detection and disease aggressiveness prediction are urgently needed. The aim of the present study was to validate DNA methylation biomarkers for non-invasive SRM detection and prognosis. The levels of methylated genes TFAP2B, TAC1, PCDH8, ZNF677, FLRT2, and FBN2 were evaluated in 165 serial urine samples prospectively collected from 39 patients diagnosed with SRM, specifically renal cell carcinoma (RCC), before and during the AS via quantitative methylation-specific polymerase chain reaction. Voided urine samples from 92 asymptomatic volunteers were used as the control. Significantly higher methylated TFAP2B, TAC1, PCDH8, ZNF677, and FLRT2 levels and/or frequencies were detected in SRM patients' urine samples as compared to the control. The highest diagnostic power (AUC = 0.74) was observed for the four biomarkers panel with 92% sensitivity and 52% specificity. Methylated PCDH8 level positively correlated with SRM size at diagnosis, while TFAP2B had the opposite effect and was related to SRM progression. To sum up, SRMs contribute significantly to the amount of methylated DNA detectable in urine, which might be used for very early RCC detection. Moreover, PCDH8 and TFAP2B methylation have the potential to be prognostic biomarkers for SRMs.

Contrast-enhanced ultrasound (CEUS) of benign and malignant renal tumors: Distinguishing CEUS features differ with tumor size

BACKGROUND

Contrast-enhanced ultrasound (CEUS) is now a guideline-recommended strategy for diagnosing renal lesions. Tumor size is related to the risk of the treatment and prognosis in renal tumors. Thus, we aim to analyze the CEUS features of solid renal tumors in relation to tumor size.

METHODS

The CEUS appearance of 156 pathologically diagnosed solid renal tumors were retrospectively analyzed. Three groups were stratified according to the tumor size (≤2 cm [group I], 2.1-4 cm [group II] and 4.1-7 cm [group III]). For each group, the features of wash-in type, enhancement degree, enhancement homogeneity, and the presence of a pseudocapsule sign were compared between benign and malignant tumors.

RESULTS

All 156 included lesions were detected by CEUS. The proportion of benign tumors in three size groups was 37.1%, 19.4%, and 20.4%, respectively. The proportion of malignant tumors was highest (80.6%) in group II, followed by group III (79.6%) and group I (62.9%). In group I, malignant and benign tumors differed significantly in the presence of a pseudocapsule sign (p = 0.015) and homogeneity (p = 0.007). In group II, the degree of enhancement differed (p = 0.02) between tumor types. In group III, the two tumor types differed in both the wash-in pattern (p = 0.015) and enhancement degree (p = 0.024). The weighted and Cohen's kappa values for the concordance between inter-observer agreement ranged from 0.31 (95% CI: 0.36-0.57) to 0.90 (95% CI: 0.77-1.00).

CONCLUSIONS

CEUS features of malignant and benign renal tumors change along with the tumor size. The use of CEUS features in the diagnosis of benign and malignant tumors requires consideration of tumor size.

Growth Kinetics and Progression Rate of Bosniak Classification Version 2019 Class III and IV Cystic Renal Masses on Imaging Surveillance

BACKGROUND. Active surveillance is increasingly used as first-line management for localized renal masses. Triggers for intervention primarily reflect growth kinetics, which have been poorly investigated for cystic masses defined by the Bosniak classification version 2019 (v2019). OBJECTIVE. The purpose of this study was to determine growth kinetics and incidence rates of progression of class III and IV cystic renal masses, as defined by the Bosniak classification v2019. METHODS. This retrospective study included 105 patients (68 men, 37 women; median age, 67 years) with 112 Bosniak v2019 class III or IV cystic renal masses on baseline renal mass protocol CT or MRI examinations performed from January 2005 to September 2021. Mass dimensions were measured. Progression was defined as any of the following: linear growth rate (LGR) of 5 mm/y or greater (representing the clinical guideline threshold for intervention), volume doubling time less than 1 year, T category increase, or N1 or M1 disease. Class III and IV masses were compared. Time to progression was estimated using Kaplan-Meier curve analysis. RESULTS. At baseline, 58 masses were class III and 54 were class IV. Median follow-up was 403 days. Median LGR for class III masses was 0.0 mm/y (interquartile range [IQR], -1.3 to 1.8 mm/y) and for class IV masses was 2.3 mm/y (IQR, 0.0-5.7 mm/y) (p < .001). LGR was at least 5 mm/y in four (7%) class III masses and 15 (28%) class IV masses (p = .005). Two patients, both with class IV masses, developed distant metastases. Incidence rate of progression for class III masses was 11.0 (95% CI, 4.5-22.8) and for class IV masses 73.6 (95% CI, 47.8-108.7) per 100,000 person-days of follow-up. Median time to progression was undefined for class III masses given the small number of progression events and 710 days for class IV masses. Hazard ratio of progression for class IV relative to class III masses was 5.1 (95% CI, 2.5-10.8; p < .001). CONCLUSION. During active surveillance of cystic masses evaluated using the Bosniak classification v2019, class IV masses grew faster and were more likely to progress than class III masses. CLINICAL IMPACT. In comparison with current active surveillance guidelines that treat class III and IV masses similarly, future iterations may incorporate relatively more intensive surveillance for class IV masses.

Using Peritumor and Intratumor Vascularity on Preoperative Imaging to Predict Fuhrman Grade Histology of Renal Tumors

Objective To investigate if peri-tumor and/or intra-tumor vasculature is associated with high grade tumor histology for renal cell carcinoma. Methods A retrospective review at a tertiary care facility was performed of patients who underwent radical nephrectomy or partial nephrectomy for a renal tumor between January 2015 to December 2020. Data of tumor characteristics was collected from final pathology reports. A single radiologist specializing in genitourinary imaging reviewed all pre-operative cross-sectional imaging for peri-tumor vessels and intra-tumor vessels. Single and multivariable logistic regression was utilized to identify variables associated with high grade tumor histology. Results The average tumor size on final pathology was 6.4 cm (Range 3.0-17.0 cm). Ninety-two patients (56.1%) had either an enlarged peri-tumor vessel (n=72), an intra-tumor vessel (n=3), or both a peri-tumor vessel and an intra-tumor vessel (n=17). Of the 92 patients with either a peri-tumor vessel or both a peri-tumor vessel and intra-tumor vessel, 60.9% of these patients had high Fuhrman grade histology on final pathology (60.9% vs 39.1%, p<0.001). Pathologic stage T1a tumors with an enlarged peri-tumor vessel on pre-operative imaging were associated with high Fuhrman grade histology (58.3% vs 41.7%, p=0.015). Across all stages, the presence of an enlarged peritumor vessel was significantly associated with high Fuhrman grade (OR: 2.37, 95% CI 1.17 - 4.9, p = 0.01). Conclusion Findings suggest that vessels surrounding small renal tumors and large renal tumors is associated with high tumor grade (FG > 3). Further research is needed to support the association of peri-tumor vessels with high tumor grade.

Deep Learning-based Deformable Registration of Dynamic Contrast-Enhanced MR Images of the Kidney

Respiratory motion is a major contributor to bias in quantitative analysis of magnetic resonance imaging (MRI) acquisitions. Deformable registration of three-dimensional (3D) dynamic contrast-enhanced (DCE) MRI data improves estimation of kidney kinetic parameters. In this study, we proposed a deep learning approach with two steps: a convolutional neural network (CNN) based affine registration network, followed by a U-Net trained for deformable registration between two MR images. The proposed registration method was applied successively across consecutive dynamic phases of the 3D DCE-MRI dataset to reduce motion effects in the different kidney compartments (i.e., cortex, medulla). Successful reduction in the motion effects caused by patient respiration during image acquisition allows for improved kinetic analysis of the kidney. Original and registered images were analyzed and compared using dynamic intensity curves of the kidney compartments, target registration error of anatomical markers, image subtraction, and simple visual assessment. The proposed deep learning-based approach to correct motion effects in abdominal 3D DCE-MRI data can be applied to various kidney MR imaging applications.

Multimodality imaging review of focal renal lesions

Background

Focal lesions of the kidney comprise a spectrum of entities that can be broadly classified as malignant tumors, benign tumors, and non-neoplastic lesions. Malignant tumors include renal cell carcinoma subtypes, urothelial carcinoma, lymphoma, post-transplant lymphoproliferative disease, metastases to the kidney, and rare malignant lesions. Benign tumors include angiomyolipoma (fat-rich and fat-poor) and oncocytoma. Non-neoplastic lesions include infective, inflammatory, and vascular entities. Anatomical variants can also mimic focal masses.

Main body of the abstract

A range of imaging modalities are available to facilitate characterization; ultrasound (US), contrast-enhanced ultrasound (CEUS), computed tomography (CT), magnetic resonance (MR) imaging, and positron emission tomography (PET), each with their own strengths and limitations. Renal lesions are being detected with increasing frequency due to escalating imaging volumes. Accurate diagnosis is central to guiding clinical management and determining prognosis. Certain lesions require intervention, whereas others may be managed conservatively or deemed clinically insignificant. Challenging cases often benefit from a multimodality imaging approach combining the morphology, enhancement and metabolic features.

Short conclusion

Knowledge of the relevant clinical details and key imaging features is crucial for accurate characterization and differentiation of renal lesions.

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 differentiation of fat-poor angiomyolipomas from papillary renal cell carcinomas: development of a predictive model

PURPOSE

To identify specific contrast-enhanced CT (CECT) findings and develop a predictive model with logistic regression to differentiate fat-poor angiomyolipomas (fpAML) from papillary renal cell carcinomas (pRCC).

METHODS

This is a single-institution retrospective study that assess CT features of histologically proven 67 pRCC and 13 fpAML. CECT variables were studied by means of univariate logistic regression. Variables included patients' demographics, tumor attenuation (unenhanced and at arterial, venous and excretory post-contrast phases), type of enhancement, morphological features (axial long and short diameters, long-short axis ratio (LSR) and tumor to kidney angle interface) and presence of visible calcifications or vessels. Those variables with a p ≤ 0.05 underwent standard stepwise logistic regression to find predictive combinations of clinical variables. Best models were evaluated by AUROC curves and were subjected to Leave-one-out cross validation to assess their robustness.

RESULTS

Odds ratio (OR) between pRCC and fpAML was statistically significant for patient's gender, tumor attenuation in arterial, venous and excretory phases, tumor's long diameter, short diameter, LSR, type of enhancement, presence of intratumoral vessels and tumor-kidney angle interface. The best predictive model resulted in an area under the curve (AUC) of 0.971 and included gender, tumor-kidney angle interface and venous attenuation with the following equation: Log(p/1 - p) = - 2.834 + 4.052 * gender +  - 0.066 * AngleInterface + 0.074 * VenousphaseHU.

CONCLUSIONS

The combination of patients' gender, tumor to kidney angle interface and venous enhancement helps to distinguish fpAML from pRCC.

Clinical and radiological findings for small renal masses under active surveillance

OBJECTIVE

To analyze the experience performing active surveillance (AS) of small renal masses (SRMs) in our center and to correlate the evolution of SRMs under AS with clinical and radiological findings.

METHODS

Patients on AS between January 2012 until May 2020 for SRMs in our center have been included. Growth rate (GR) per year was analyzed and correlated with radiographic features. Patients with growth kinetics higher than 5mm/year during follow up were offered active treatment.

RESULTS

73 patients were included in AS: the mean age was 75.7 years, a mean initial tumour size of 21.2 mm, and a mean growth rate of 2.05 mm/year. Around 60 % had an ASA score of 3. The tumor size did not change over time in 43% of cases; in 4% we noticed a regression in size and in 52% of cases growth during follow-up (38% 1-5mm/year and 14% more than 5 mm/year). Delayed active treatment was indicated in 16 (21%) of cases. Treatment applied was as following: 2 radiofrequency ablations, 6 radical and 8 partial nephrectomies. A weak correlation was found between initial size and growth rate (r = 0.38, P = 0.02). No significant association was detected regarding any of the analyzed radiological findings and GR. With a mean follow up time of 33 months none of the patients presented metastatic progression.

CONCLUSION

Active surveillance is a feasible option for management of SRMs in selected patients without jeopardizing oncological safety. In our series, no clinical or radiological characteristics for predicting tumour growth were found.

A MEST up classification? Review of the re-classification of mixed epithelial and stromal tumor and adult cystic nephroma for the abdominal radiologist

Mixed epithelial and stromal tumor (MEST) and the tumor formerly known as adult cystic nephroma (ACN) are uncommon renal tumors that have historically been described as separate entities in terms of histologic and imaging findings. However, these entities share many epidemiologic, radiologic, and pathologic features. While recent surgical and pathological literature has supported classifying MEST and ACN within the same tumor family, most radiologists and radiology texts continue to describe MEST and ACN as separate entities.

Imaging Characterization of Renal Masses

The detection of a renal mass is a relatively frequent occurrence in the daily practice of any Radiology Department. The diagnostic approaches depend on whether the lesion is cystic or solid. Cystic lesions can be managed using the Bosniak classification, while management of solid lesions depends on whether the lesion is well-defined or infiltrative. The approach to well-defined lesions focuses mainly on the differentiation between renal cancer and benign tumors such as angiomyolipoma (AML) and oncocytoma. Differential diagnosis of infiltrative lesions is wider, including primary and secondary malignancies and inflammatory disease, and knowledge of the patient history is essential. Radiologists may establish a possible differential diagnosis based on the imaging features of the renal masses and the clinical history. The aim of this review is to present the contribution of the different imaging techniques and image guided biopsies in the diagnostic management of cystic and solid renal lesions.