Partial Nephrectomy for Presumed Renal-Cell Carcinoma: Incidence, Predictors, and Perioperative Outcomes of Benign Lesions

Can multiparametric MRI clear cell likelihood scores differentiate fat-Poor AML from CcRCC in subcentimeter lesions?

OBJECTIVE

To investigate the potential of multiparametric MRI clear cell likelihood scores (ccLS) for differentiating between fat-poor angiomyolipoma (AML) and clear cell renal cell carcinoma (ccRCC) in subcentimeter Lesions (1 cm or smaller).

MATERIALS AND METHODS

This retrospective study included consecutive patients with subcentimeter renal masses who underwent multiparametric MRI between September 2009 and September 2022 across three hospitals. Clinical and MRI findings were analyzed to differentiate between fat-poor AML and ccRCC. Lesions were categorized using the ccLS and receiver operating characteristic curve analysis was performed to assess ccLS performance.

RESULTS

Thirty-eight patients (mean age: 52 years ± 12; 19 women) with 39 lesions were included. Of the 39 lesions [mean size: 9.1 mm ± 1.0 (range, 6.0-10.0 mm)], 20 (51%) were ccRCC and 19 (49%) were fat-poor AML. Compared to the ccRCC, subcentimeter fat-poor AMLs were more likely to show hypointensity on T2WI (P < 0.001), homogeneous enhancement (P = 0.010), the presence of microscopic fat (P = 0.036), and the absence of a pseudocapsule (P = 0.020). The diagnostic percentage of fat-poor AML was 47% for a ccLS of 1 or 2, and ccRCC accounted for 75% in the ccLS 4 or 5 category. The AUC for discrimination was 0.846 (95% CI: 0.695-0.941, P < 0.001), with a sensitivity of 75.00% (95% CI: 50.9-91.3) and a specificity of 89.47% (95% CI: 66.9-98.7).

CONCLUSION

Multiparametric MRI clear cell likelihood scores can potentially be used to differentiate between fat-poor AML and ccRCC in lesions 1 cm or smaller.

A National Study of the Rate of Benign Pathology After Partial Nephrectomy for T1 Renal Cell Carcinoma: Should We Be Satisfied?

Objectives: To determine the rate of benign pathology in cT1 tumors following partial nephrectomy in the Netherlands, thereby evaluating the rate of overtreatment. Methods: Data were collected from a nationwide database containing histopathology of resected renal tissue from 2014 to 2022. Patients who underwent partial nephrectomy for suspected RCC staged T1a-b were extracted for analysis. Data are shown in percentages, and multivariable logistic regression was performed to determine predictive factors for benign pathology. Results: 3409 cases were analyzed, of which 403 (12%) were benign and 3006 (88%) malignant. Subtype analysis showed 2126 (62%) cases of clear-cell RCC, followed by 604 (18%) of papillary RCC and 344 (10%) oncocytomas. Mean age was 63 years among patients with malignant pathology versus 65 years for patients with benign lesions (p < 0.001). Mean tumor size was 3.2 cm for malignant pathology and 2.9 cm for benign (p < 0.001). The rates of benign and malignant pathology did not change between 2014 and 2022 (p = 0.377). Multivariable regression showed age ≥ 65 years (65-79 years [OR 1.881, p = 0.002], ≥ 80 years [OR 3.642, p < 0.001]) and tumor size (OR 0.793, p < 0.001) as predictors for benign pathology. The main limitation of this study is that we do not know the biopsy rate of our cohort. Conclusion: This study reports a low rate of 12% benign pathology after partial nephrectomy in the Netherlands. It remains debatable whether these rates are acceptable, or if renal tumor biopsies should be utilized more frequently to reduce overtreatment.

Frequency of benign tumors after partial nephrectomy and the association between malignant tumor findings and preoperative clinical parameters

BACKGROUND

Partial nephrectomy (PN) has become the dominant treatment modality for cT1 renal tumor lesions. Tumors suspected of malignant potential are indicated for surgery, but some are histologically classified as benign lesions after surgery. This study aims to analyze the number of benign findings after PN according to definitive histology and to evaluate whether there is an association between malignant tumor findings and individual factors.

METHODS

The retrospective study included 555 patients who underwent open or robotic-assisted PN for a tumor in our clinic from January 2013 to December 2020. The cohort was divided into groups according to definitive tumor histology (malignant tumors vs. benign lesions). The association of factors (age, sex, tumor size, R.E.N.A.L.) with the malignant potential of the tumor was further evaluated.

RESULTS

In total, 462 tumors were malignant (83%) and 93 benign (17%). Of the malignant tumors, 66% were clear-cell RCC (renal cell carcinoma), 12% papillary RCC, and 6% chromophobe RCC. The most common benign tumor was oncocytoma in 10% of patients, angiomyolipoma in 2%, and papillary adenoma in 1%. In univariate analysis, there was a higher risk of malignant tumor in males (OR 2.13, 95% CI 1.36-3.36, p = 0.001), a higher risk of malignancy in tumors larger than 20 mm (OR 2.32, 95% CI 1.43-3.74, p < 0.001), and a higher risk of malignancy in tumors evaluated by R.E.N.A.L. as tumors of intermediate or high complexity (OR 2.8, 95% CI 1.76-4.47, p < 0.001). In contrast, there was no association between older age and the risk of malignant renal tumor (p = 0.878).

CONCLUSIONS

In this group, 17% of tumors had benign histology. Male sex, tumor size greater than 20 mm, and intermediate or high R.E.N.A.L. complexity were statistically significant predictors of malignant tumor findings.

Deep Learning Assessment of Small Renal Masses at Contrast-enhanced Multiphase CT

Background Accurate characterization of suspicious small renal masses is crucial for optimized management. Deep learning (DL) algorithms may assist with this effort. Purpose To develop and validate a DL algorithm for identifying benign small renal masses at contrast-enhanced multiphase CT. Materials and Methods Surgically resected renal masses measuring 3 cm or less in diameter at contrast-enhanced CT were included. The DL algorithm was developed by using retrospective data from one hospital between 2009 and 2021, with patients randomly allocated in a training and internal test set ratio of 8:2. Between 2013 and 2021, external testing was performed on data from five independent hospitals. A prospective test set was obtained between 2021 and 2022 from one hospital. Algorithm performance was evaluated by using the area under the receiver operating characteristic curve (AUC) and compared with the results of seven clinicians using the DeLong test. Results A total of 1703 patients (mean age, 56 years ± 12 [SD]; 619 female) with a single renal mass per patient were evaluated. The retrospective data set included 1063 lesions (874 in training set, 189 internal test set); the multicenter external test set included 537 lesions (12.3%, 66 benign) with 89 subcentimeter (≤1 cm) lesions (16.6%); and the prospective test set included 103 lesions (13.6%, 14 benign) with 20 (19.4%) subcentimeter lesions. The DL algorithm performance was comparable with that of urological radiologists: for the external test set, AUC was 0.80 (95% CI: 0.75, 0.85) versus 0.84 (95% CI: 0.78, 0.88) (P = .61); for the prospective test set, AUC was 0.87 (95% CI: 0.79, 0.93) versus 0.92 (95% CI: 0.86, 0.96) (P = .70). For subcentimeter lesions in the external test set, the algorithm and urological radiologists had similar AUC of 0.74 (95% CI: 0.63, 0.83) and 0.81 (95% CI: 0.68, 0.92) (P = .78), respectively. Conclusion The multiphase CT-based DL algorithm showed comparable performance with that of radiologists for identifying benign small renal masses, including lesions of 1 cm or less. Published under a CC BY 4.0 license. Supplemental material is available for this article.

Rate of benign histology after resection of suspected renal cell carcinoma: multicenter comparison between Korea and the United States

BACKGROUND

In the United States, the rate of benign histology among resected renal tumors suspected to be malignant is increasing. We evaluated the rates in the Republic of Korea and assessed the racial effect using recent multi-institutional Korean-United States data.

METHODS

We conducted a multi-institutional retrospective study of 11,529 patients (8,812 from The Republic of Korea and 2,717 from the United States) and compared the rates of benign histology between the two countries. To evaluate the racial effect, we divided the patients into Korean, Asian in the US, and Non-Asian in the US.

RESULTS

The rates of benign histology and small renal masses in Korean patients were significantly lower than that in United States patients (6.3% vs. 14.3%, p < 0.001) and (≤ 4 cm, 7.6% vs. 19.5%, p < 0.001), respectively. Women, incidentaloma, partial nephrectomy, minimally invasive surgery, and recent surgery were associated with a higher rate of benign histology than others.

CONCLUSIONS

In Korea, the rate of benign histology among resected renal tumors was significantly lower than that in the United States. This disparity could be caused by environmental or cultural differences rather than racial differences. Our findings suggest that re-evaluating current context-specific standards of care is necessary to avoid overtreatment.

Pre-operative Serum Albumin as a Potential Predictor of Benign Lesions in Renal Masses

BACKGROUND/AIM

We investigated pre-operative factors for predicting whether renal masses are benign in order to facilitate the selection of optimal candidates for pre-operative biopsy.

PATIENTS AND METHODS

We evaluated 278 patients with renal masses suspected to be clinically T1 or T2 renal cell carcinoma. All patients had undergone a partial or radical nephrectomy. Pre-operative parameters, including patient characteristics, tumor size, and blood tests, were utilized to predict which lesions were benign.

RESULTS

Twenty-five lesions (9.0%) were benign. Multivariate analysis showed that female sex [odds ratio (OR)=2.92, p=0.016], serum albumin ≥4.3 g/dl (OR=3.50, p=0.013), and tumor size <23 mm (OR=3.96, p=0.002) were significant independent factors for benign renal masses. The incidence of benign lesions in cases with all three factors (female sex, higher serum albumin, and smaller tumor size) was 4 of 16 (25.0%), which was significantly higher (p=0.037) than that in all cases (25/278; 9.0%).

CONCLUSION

Relatively high pre-operative serum albumin levels may be a predictor of benign lesions when associated with female sex and smaller tumor size.

Apparent Diffusion Coefficient Map-Based Texture Analysis for the Differentiation of Chromophobe Renal Cell Carcinoma from Renal Oncocytoma

Preoperative imaging differentiation between ChRCC and RO is difficult with conventional subjective evaluation, and the development of quantitative analysis is a clinical challenge. Forty-nine patients underwent partial or radical nephrectomy preceded by MRI and followed by pathological diagnosis with ChRCC or RO (ChRCC: n = 41, RO: n = 8). The whole-lesion volume of interest was set on apparent diffusion coefficient (ADC) maps of 1.5T-MRI. The importance of selected texture features (TFs) was evaluated, and diagnostic models were created using random forest (RF) analysis. The Mean Decrease Gini as calculated through RF analysis was the highest for mean_ADC_value. ChRCC had a significantly lower mean_ADC_value than RO (1.26 vs. 1.79 × 10−3 mm2/s, p < 0.0001). Feature selection by the Boruta method identified the first-quartile ADC value and GLZLM_HGZE as important features. ROC curve analysis showed that there was no significant difference in the classification performances between the mean_ADC_value-only model and the Boruta model (AUC: 0.954 vs. 0.969, p = 0.236). The mean ADC value had good predictive ability for the distinction between ChRCC and RO, comparable to that of the combination of TFs optimized for the evaluated cohort. The mean ADC value may be useful in distinguishing between ChRCC and RO.

An Ultrasonic-Based Radiomics Nomogram for Distinguishing Between Benign and Malignant Solid Renal Masses

Objectives

This study was conducted in order to develop and validate an ultrasonic-based radiomics nomogram for diagnosing solid renal masses.

Methods

Six hundred renal solid masses with benign renal lesions (n = 204) and malignant renal tumors (n = 396) were divided into a training set (n = 480) and a validation set (n = 120). Radiomics features were extracted from ultrasound (US) images preoperatively and then a radiomics score (RadScore) was calculated. By integrating the RadScore and independent clinical factors, a radiomics nomogram was constructed. The diagnostic performance of junior physician, senior physician, RadScore, and radiomics nomogram in identifying benign from malignant solid renal masses was evaluated based on the area under the receiver operating characteristic curve (ROC) in both the training and validation sets. The clinical usefulness of the nomogram was assessed using decision curve analysis (DCA).

Results

The radiomics signature model showed satisfactory discrimination in the training set [area under the ROC (AUC), 0.887; 95% confidence interval (CI), 0.860–0.915] and the validation set (AUC, 0.874; 95% CI, 0.816–0.932). The radiomics nomogram also demonstrated good calibration and discrimination in the training set (AUC, 0.911; 95% CI, 0.886–0.936) and the validation set (AUC, 0.861; 95% CI, 0.802–0.921). In addition, the radiomics nomogram model showed higher accuracy in discriminating benign and malignant renal masses compared with the evaluations by junior physician (DeLong p = 0.004), and the model also showed significantly higher specificity than the senior and junior physicians (0.93 vs. 0.57 vs. 0.46).

Conclusions

The ultrasonic-based radiomics nomogram shows favorable predictive efficacy in differentiating solid renal masses.

Simultaneous robotic partial nephrectomy for bilateral renal masses

PURPOSE

There is currently no consensus regarding the optimal treatment strategy for patients presenting with synchronous bilateral renal masses. The decision to perform bilateral procedures on the same intervention or in staged procedures is debated. The aim of this manuscript is to analyse the outcomes of simultaneous robot-assisted partial nephrectomy (RAPN) in a series of patients with bilateral renal masses treated at five Italian robotic institutions.

METHODS

Data from a prospectively maintained multi-institutional database on patients subjected to simultaneous RAPN between November 2011 and July 2019 were reviewed. RAPNs were performed with da Vinci Si or Xi surgical system by expert robotic surgeons. Baseline demographics and clinical features, peri- and post-operative data were collected.

RESULTS

Overall, 27 patients underwent simultaneous bilateral RAPN, and 54 RAPNs were performed without need of conversion; median operative time was 250 minutes, median estimated blood loss was 200 mL. Renal artery clamping was needed for 27 (50%) RAPNs with a median warm ischemia time of 15 minutes and no case of acute kidney injury. Complications were reported in 7 (25.9%) patients, mainly represented by Clavien 2 events (6 blood transfusions). Positive surgical margins were assessed in 2 (3.7%) of the renal cell carcinoma. At the median follow-up of 30 months, recurrence-free survival was 100%.

CONCLUSION

Our data showed that, in selected patients and expert hands, simultaneous bilateral RAPNs could be a safe and feasible procedure with promising results for the treatment of bilateral synchronous renal masses.

Renal Mass Biopsy

Kidney cancer accounts for 2% of cancer related deaths. Historically, a patient with a solid renal mass would undergo surgery without biopsy given the previously low diagnostic yield of biopsy and the fear of tumor seeding. This led to a high rate of resection for benign masses. With the rising incidence of renal masses discovered on imaging, improvements in biopsy technique and advancements in pathologic evaluation of biopsy samples of renal masses, renal mass biopsy now plays an important role in selected patients with renal masses. Coaxial core needle biopsy is the preferred technique with a low rate of complications and a high diagnostic yield. This article will discuss indications, methods, utility, limitations and complications of renal mass biopsy.

Predictive value of contrast-enhanced ultrasound combined with conventional ultrasound in solid renal parenchymal lesions

OBJECTIVE

This study aimed to develop a model to predict the risk of malignancy in solid renal parenchymal lesions based on the imaging features of combined conventional and contrast-enhanced ultrasound (CEUS).

METHODS

A retrospective review was performed among patients with focal solid renal parenchymal lesions on ultrasound images. Ultrasound features were characterized by two experienced radiologists independently. A multiple logistic regression analysis was performed to determine the most relevant features and to estimate the risk of malignancy. Scoring and counting methods were developed based on the most relevant features. The diagnostic performance was evaluated by the sensitivity, specificity, positive predictive value, negative predictive value and area under the receiver operating characteristic curve (AUC).

RESULTS

A total of 519 renal lesions were included in this study. The conventional ultrasound features of diameter, echogenicity, hypoechoic rim and the CEUS feature of heterogeneity were identified as the most relevant features for prediction of malignancy. The sensitivity and specificity for the logistic regression model, the scoring method and the counting method were 95.3 and 93.4%, 93.8 and 87.8%, 88.8 and 93.9%, respectively. The logistic model had the best performance for diagnosing malignant renal lesions with AUC of 0.978, compared with the scoring method and the counting method with AUCs of 0.958 and 0.965.

CONCLUSION

The combination of contrast-enhanced ultrasound with conventional ultrasound improved the diagnostic performance of solid renal lesions based on the logistic regression model.

ADVANCES IN KNOWLEDGE

In this study, we revealed that the combination of CEUS and conventional ultrasound provided higher accuracy for diagnosing malignant renal tumors.

Deep learning for end-to-end kidney cancer diagnosis on multi-phase abdominal computed tomography

In 2020, it is estimated that 73,750 kidney cancer cases were diagnosed, and 14,830 people died from cancer in the United States. Preoperative multi-phase abdominal computed tomography (CT) is often used for detecting lesions and classifying histologic subtypes of renal tumor to avoid unnecessary biopsy or surgery. However, there exists inter-observer variability due to subtle differences in the imaging features of tumor subtypes, which makes decisions on treatment challenging. While deep learning has been recently applied to the automated diagnosis of renal tumor, classification of a wide range of subtype classes has not been sufficiently studied yet. In this paper, we propose an end-to-end deep learning model for the differential diagnosis of five major histologic subtypes of renal tumors including both benign and malignant tumors on multi-phase CT. Our model is a unified framework to simultaneously identify lesions and classify subtypes for the diagnosis without manual intervention. We trained and tested the model using CT data from 308 patients who underwent nephrectomy for renal tumors. The model achieved an area under the curve (AUC) of 0.889, and outperformed radiologists for most subtypes. We further validated the model on an independent dataset of 184 patients from The Cancer Imaging Archive (TCIA). The AUC for this dataset was 0.855, and the model performed comparably to the radiologists. These results indicate that our model can achieve similar or better diagnostic performance than radiologists in differentiating a wide range of renal tumors on multi-phase CT.

Radiomics in Renal Cell Carcinoma-A Systematic Review and Meta-Analysis

Simple Summary

Radiomics may answer questions where the conventional interpretation of medical imaging has limitations. The aim of our systematic review and meta-analysis was to assess the (current) status of evidence in the application of radiomics in the field of renal masses. We focused on its role in diagnosis, sub-entity discrimination and treatment response assessment in renal cell carcinoma (RCC) and benign renal masses. Our quantitative synthesis showed promising results in discrimination of tumor dignity, nevertheless, the value added to human assessment remains unclear and should be the focus of future research. Furthermore, the benefit regarding treatment response assessment remains unclear as well, since the existing studies are investigating already abandoned systemic therapies (ST), which no longer represent the current “reference” standard. Open science could enable to establish technical and clinical validity of radiomic signatures prior to the incorporation of radiomics into everyday clinical practice.

Abstract

Radiomics may increase the diagnostic accuracy of medical imaging for localized and metastatic RCC (mRCC). A systematic review and meta-analysis was performed. Doing so, we comprehensively searched literature databases until May 2020. Studies investigating the diagnostic value of radiomics in differentiation of localized renal tumors and assessment of treatment response to ST in mRCC were included and assessed with respect to their quality using the radiomics quality score (RQS). A total of 113 out of 1098 identified studies met the criteria and were included in qualitative synthesis. Median RQS of all studies was 13.9% (5.0 points, IQR 0.25–7.0 points), and RQS increased over time. Thirty studies were included into the quantitative synthesis: For distinguishing angiomyolipoma, oncocytoma or unspecified benign tumors from RCC, the random effects model showed a log odds ratio (OR) of 2.89 (95%-CI 2.40–3.39, p < 0.001), 3.08 (95%-CI 2.09–4.06, p < 0.001) and 3.57 (95%-CI 2.69–4.45, p < 0.001), respectively. For the general discrimination of benign tumors from RCC log OR was 3.17 (95%-CI 2.73–3.62, p < 0.001). Inhomogeneity of the available studies assessing treatment response in mRCC prevented any meaningful meta-analysis. The application of radiomics seems promising for discrimination of renal tumor dignity. Shared data and open science may assist in improving reproducibility of future studies.

The value of 99mTc-sestamibi single-photon emission computed tomography-computed tomography in the evaluation and risk stratification of renal masses

INTRODUCTION

Differentiation of renal cell carcinoma (RCC) from oncocytoma is a common diagnostic dilemma. A few studies have shown that ^99mTc-sestamibi (MIBI) imaging has the potential to characterize indeterminate renal masses. This comparative study evaluated the utility of MIBI single-photon emission computed tomography-computed tomography (SPECT-CT) in the assessment and risk stratification of renal masses.

METHODS

A total of 29 patients with 31 renal masses who had cross-sectional imaging and MIBI SPECT-CT were included. Lesions were categorized as either MIBI-positive or -negative on SPECT-CT. Individual lesion density ranged from 22-56 Hounsfield units (HU) on the non-contrast CT part of SPECT-CT. Quantitative relative MIBI uptake was calculated by measuring tumor to ipsilateral renal parenchymal uptake. The imaging results were correlated with histopathology.

RESULTS

All oncocytic lesions, including seven oncocytomas and one hybrid oncocytic chromophobe tumor (100%), were positive on MIBI. One chromophobe RCC showed low-grade MIBI uptake. The remaining RCC subtypes, including 15 clear-cell, four papillary, two mixed clear-cell and papillary, and one chromophobe, were MIBI-negative. The quantitative relative tumor uptake showed statistically significant higher uptake in the low-risk/oncocytic lesions compared to RCCs.

CONCLUSIONS

This study demonstrates that MIBI SPECT-CT is valuable in the characterization of indeterminate renal masses. The combination of MIBI uptake on SPECT and lesion density on non-contrast CT can be used for risk stratification of renal masses. This technique may reduce the need for further imaging (multiphasic CT or magnetic resonance imaging), renal mass biopsy, or surgical resection of low-risk renal masses. Subsequently, more patients could be followed with active surveillance.

Prevalence of benign pathology after partial nephrectomy for suspected renal tumor: A systematic review and meta-analysis

OBJECTIVE

To investigate the overall prevalence of benign pathology after partial nephrectomy (PN) and identify predictive factors for benign pathology after PN.

METHODS

A systematic review was performed following the PRISMA guidelines. PubMed/Medline, Embase, and the Cochrane Library were searched up to January 2019PRISMA guidelines. The data for the meta-analysis and network meta-analysis were pooled using a random-effects model.

RESULTS

There were 144 studies included in the final analysis, which was comprised of 79 observational studies (n = 37,300) and 65 comparative studies (n = 18,552). The overall prevalence rate of benign pathology after PN was 0.19 (95% CI: 0.18-0.21). According to the procedure types, the prevalence rate of benign pathology was 0.17 (95% CI: 0.15-0.19), 0.24 (95% CI: 0.22-0.27), and 0.16 (95% CI: 0.15-0.18) in open partial nephrectomy, laparoscopic partial nephrectomy, and robot-assisted laparoscopic partial nephrectomy, respectively. The significant moderating factors were gender, publication year, the origin of the study, and procedure types. The three most common benign pathology types were oncocytomas, angiomyolipomas, and renal cysts (44.50%, 30.20%, and 10.99%, respectively).

CONCLUSIONS

The overall prevalence of benign pathology after PN was not low and it was affected by female gender, studies published before 2010, studies originating from Western areas, and laparoscopic procedure types.

MR texture analysis in differentiating renal cell carcinoma from lipid-poor angiomyolipoma and oncocytoma

OBJECTIVES

To assess the utility of magnetic resonance texture analysis (MRTA) in differentiating renal cell carcinoma (RCC) from lipid-poor angiomyolipoma (lpAML) and oncocytoma.

METHODS

After ethical approval, 42 patients with 54 masses (34 RCC, 14 lpAML and six oncocytomas) who underwent MRI on a 1.5 T scanner (Avanto, Siemens, Erlangen, Germany) between January 2011 and December 2012 were retrospectively included in the study. MRTA was performed on the TexRAD research software (Feedback Plc., Cambridge, UK) using free-hand polygonal region of interest (ROI) drawn on the maximum cross-sectional area of the tumor to generate six first-order statistical parameters. The Mann-Whitney U test was used to look for any statically significant difference. The receiver operating characteristic (ROC) curve analysis was done to select the parameter with the highest class separation capacity [area under the curve (AUC)] for each MRI sequence.

RESULTS

Several texture parameters on MRI showed high-class separation capacity (AUC > 0.8) in differentiating RCC from lpAML and oncocytoma. The best performing parameter in differentiating RCC from lpAML was mean of positive pixels (MPP) at SSF 2 (AUC: 0.891) on DWI b500. In differentiating RCC from oncocytoma, the best parameter was mean at SSF 0 (AUC: 0.935) on DWI b1000.

CONCLUSIONS

MRTA could potentially serve as a useful non-invasive tool for differentiating RCC from lpAML and oncocytoma.

ADVANCES IN KNOWLEDGE

There is limited literature addressing the role of MRTA in differentiating RCC from lpAML and oncocytoma. Our study demonstrated several texture parameters which were useful in this regard.

Use of Contrast Ultrasound for Renal Mass Evaluation

An introduction to the expanding modality of contrast-enhanced ultrasound is provided, along with basics on contrast agents and technique. The contrast ultrasound findings of multiple renal tumors are reviewed with examples, including clear cell renal cell carcinoma, papillary renal cell carcinoma, chromophobe renal cell carcinoma, other rare renal cell carcinoma subtypes, oncocytoma, upper tract urothelial carcinoma, lymphoma, and angiomyolipoma, followed also by brief discussions of renal infections and pseudolesions.

Gender-Related Approach to Kidney Cancer Management: Moving Forward

Men are more frequently diagnosed with kidney cancer than women, with a more aggressive histology, larger tumors, a higher grade and stage, and worse oncological outcomes. Smoking habits and sex steroid hormones seem to have a possible role in explaining these gender disparities. Moreover, the expression of genes involved in tumor growth and immune response in kidney cancer varies between men and women, having an impact on the gender-related response to oncological therapy, such as anti-angiogenic drugs and immunotherapy. Recent advances have been made in our understanding of the molecular and genetic mechanisms involved in kidney cancer, which could partially explain the gender differences, and they are summarized in this paper. However, other key mechanisms, which fully clarify the striking clinical gender-related differences observed in kidney cancer, are not completely understood at present. We reviewed and summarized the most relevant publications about the relationship between gender and kidney cancer. Efforts should be made to progress in bench and clinical research on gender-related signatures and disparities, and their impact on the clinical management of kidney cancer.

Outcomes and predictors of benign histology in patients undergoing robotic partial or radical nephrectomy for renal masses: a multicenter study

Introduction

Theaim of this study was to assess preoperative factors associated with benign histology in patients undergoing surgical removal of a renal mass and to analyze outcomes of robotic partial nephrectomy (PN) and radical nephrectomy (RN) for these masses.

Material and methods

Overall, 2,944 cases (543 benign and 2,401 malignant) who underwent robotic PN and RN between 2003–2018 at 10 institutions worldwide were included. The assessment of the predictors of benign histology was made at the final surgical pathology report. Descriptive statistics, Mann-Whitney U, Pearson’s χ², and logistic regression analysis were used.

Results

Patients in the benign group were mostly female (61 vs. 33%; p <0.001), with lower body mass index (BMI) (26.0 vs. 27.1 kg/m²; p <0.001). The benign group presented smaller tumor size (2.8 vs. 3.5 cm; p <0.001), R.E.N.A.L. score (6.0 vs. 7.0; p <0.001). There was a lower rate of hilar (11 vs.18%; p = 0.001), cT≥3 (1 vs. 4.5%; p <0.001) tumors in the benign group. There was a statistically significant higher rate of PN in the benign group (97 vs. 86%; p <0.001) as well as a statistically significant lower 30-day re-admission rate (2 vs. 5%; p = 0.081). Multivariable analysis showed male gender (OR: 0.52; p <0.001), BMI (OR: 0.95; p <0.001), and cT3a (OR: 0.22; p = 0.005) to be inversely associated to benign histology.

Conclusions

In 18% of cases, a benign histologic type was found. Only 3% of these tumors were treated with RN. Female gender, lower BMI, and higher T staging showed to be independent predictors of benign histology.

Association of Prevalence of Benign Pathologic Findings After Partial Nephrectomy With Preoperative Imaging Patterns in the United States From 2007 to 2014

Importance

Although the intent of nephron-sparing surgery is to eradicate malignant tumors found on preoperative imaging, benign masses often cannot be differentiated from malignant tumors. However, in the past there have been discrepancies in the reported percentages of benign masses removed by partial nephrectomy (PNx).

Objective

To investigate the annual trend of prevalence of benign pathologic findings after PNx and to investigate what potential factors are associated with this prevalence.

Design, Setting, and Participants

A total of 18 060 patients who underwent PNx between 2007 and 2014 were selected from Truven Health MarketScan Research Databases. We selected those patients who underwent PNx as an inpatient from 2007 and set the surgery date as the index date. Overall, a total of 21 445 patients with International Classification of Diseases, Ninth Revision, Clinical Modification code of 55.4 were identified from 2007 to 2015.

Main Outcomes and Measures

The annual trend of benign pathologic findings was described as an actual number and as a proportion. Univariate and multiple analyses were performed to investigate factors predictive of a benign final pathologic diagnosis, including type of preoperative imaging modality or performance of a renal mass biopsy.

Results

Among the 18 060 patients, mean (SD) age was 57 (12) years, and there were 10637 (58.9%) men and 7423 (41.1%) women. The overall prevalence of benign pathologic findings was 30.9% and the annual trends demonstrated a prevalence of over 30% for nearly every year of the study period. On univariate analysis, the performance of magnetic resonance imaging (MRI) and renal mass biopsy was associated with benign pathologic findings (P = .02 and P < .001, respectively). On multivariable analysis, female sex (odds ratio [OR], 0.62; 95% CI, 0.58-0.66; P < .001), older age (>65 years) (OR, 0.99; 95% CI, 0.99-0.99; P < .001), and computed tomography (CT) only preoperative imaging (OR, 1.16; 95% CI, 1.05-1.28; P = .004) were associated with benign pathologic findings after PNx.

Conclusions and Relevance

We found that the overall prevalence of benign pathologic findings after PNx was higher than the literature suggests, with consistent year-over-year rates exceeding 30%. Female sex, older age (>65 years), and CT only preoperative imaging were predictive of a benign tumor. Further elucidation concerning covariates associated with a benign diagnosis should be the focus of future investigations to identify a cohort of patients who could potentially avoid unnecessary surgical intervention.

Bosniak Classification of Cystic Renal Masses, Version 2019: An Update Proposal and Needs Assessment

Cystic renal cell carcinoma (RCC) is almost certainly overdiagnosed and overtreated. Efforts to diagnose and treat RCC at a curable stage result in many benign neoplasms and indolent cancers being resected without clear benefit. This is especially true for cystic masses, which compared with solid masses are more likely to be benign and, when malignant, less aggressive. For more than 30 years, the Bosniak classification has been used to stratify the risk of malignancy in cystic renal masses. Although it is widely used and still effective, the classification does not formally incorporate masses identified at MRI or US or masses that are incompletely characterized but are highly likely to be benign, and it is affected by interreader variability and variable reported malignancy rates. The Bosniak classification system cannot fully differentiate aggressive from indolent cancers and results in many benign masses being resected. This proposed update to the Bosniak classification addresses some of these shortcomings. The primary modifications incorporate MRI, establish definitions for previously vague imaging terms, and enable a greater proportion of masses to enter lower-risk classes. Although the update will require validation, it aims to expand the number of cystic masses to which the Bosniak classification can be applied while improving its precision and accuracy for the likelihood of cancer in each class.

Differentiating between malignant and benign renal tumors: do IVIM and diffusion kurtosis imaging perform better than DWI?

OBJECTIVE

To quantitatively compare the diagnostic values of conventional diffusion-weighted imaging (DWI), intravoxel incoherent motion (IVIM), and diffusion kurtosis imaging (DKI) in differentiating between malignant and benign renal tumors.

METHODS

Multiple b value DWIs and DKIs were performed in 180 patients with renal tumors, which were divided into clear cell renal cell carcinoma (ccRCC), non-ccRCC, and benign renal tumor group. The apparent diffusion coefficient (ADC), true diffusivity (D), pseudo-diffusion coefficient (D*), perfusion fraction (f), mean kurtosis (MK), and mean diffusivity (MD) maps were calculated. The diagnostic efficacy of various diffusion parameters for predicting malignant renal tumors was compared.

RESULTS

The ADC, D, and MD values of ccRCCs were higher, while D*, f, and MK values were lower than those of benign renal tumors (all p < 0.025). The D* and f values of non-ccRCCs were lower than those of benign renal tumors (p = 0.002 and p < 0.001, respectively). The difference of ADC, D, MD, and MK values between non-ccRCCs and benign renal tumors was not statistically significant (p > 0.05). The ADC, D, MD, and f values of ccRCCs were higher, while MK values were lower than those of non-ccRCCs (all p < 0.001). The AUC values of ADC, D, D*, f, MK, and MD were 0.849, 0.891, 0.708, 0.656, 0.862, and 0.838 for differentiating ccRCCs from benign renal tumors, respectively. The AUC values of D* and f were 0.772 and 0.866 for discrimination between non-ccRCCs and benign renal tumors, respectively.

CONCLUSION

IVIM parameters are the best, while DWI and DKI parameters have similar performance in differentiating malignant and benign renal tumors.

KEY POINTS

• The D value is the best parameter for differentiating ccRCC from benign renal tumors. • The f value is the best parameter for differentiating non-ccRCC from benign renal tumors. • Conventional DWI and DKI have similar performance in differentiating malignant and benign renal tumors.

New MRI series for kidney evaluation: Saving time and money

OBJECTIVES

This study investigates the diagnostic performance of a new T1 imaging series, generated by the digital subtraction of the opposed phase from in phase T ₁ weighted images, in MRI for renal angiomyolipoma (AML) evaluation.

METHODS

This retrospective study involved 96 patients, 63 (65.6%) with at least one renal AML and 33 (34.4%) healthy patients. Two radiologists having different experience retrospectively reviewed two MR imaging series, starting with in and out-phase T ₁ weighted images and then the new subtracted T1 images, in which AML appeared white on black background. The presence, number, location, and dimensions of the AMLs, and reading time were collected separately for the two kidneys. Statistical analysis was carried out using the appropriate tests.

RESULTS

The number of lesions identified and the evaluation of lesion dimension did not statistically differ between the different MR imaging series evaluated, without interobserver variability. Both percentage agreement of the total number of observations and the κ coefficient showed very good agreement between the radiologists. The median time for the diagnosis was statistically lower when using the subtracted T1 imaging series for both observers with a median gain from 6.5 to 15 s per identified lesion, resulting in a total time-saving of more than half (52.9%), in both patients with and without AMLs, and in patients with a single or with more than one AML (p < 0.001).

CONCLUSIONS

The new subtracted T1 imaging series proved to be reliable in identifying fat-containing renal lesions, by both expert and non-expert radiologists, resulting in a saving of both time and money. Moreover, this new subtracted T1 imaging series could be an effective tool in non-dedicated kidney examinations in which a faster reading is advisable.

ADVANCES IN KNOWLEDGE

The opportunity of using a single set of MRI images in kidney evaluation for identifying fat-containing lesions, considerably reducing reading time, resulting in cost-effectiveness.

National trends of preoperative imaging modalities before partial nephrectomy for renal masses in the U.S. from 2007-2015

INTRODUCTION

Although the performance of partial nephrectomies (PN) for renal masses has increased rapidly over the years, only a few studies have investigated the frequency and patterns of preoperative imaging modalities. The aim of this study was to investigate the frequency and patterns in preoperative imaging modalities before PN.

METHODS

A total of 21 445 patients who underwent PN between 2007 and 2015 were selected from a national representative population in the MarketScan database and included in this study. The annual incidence and proportion of PN, as well as the use of each preoperative imaging modality were analyzed.

RESULTS

Both annual crude number and frequency rate of PN decreased or became static since 2012. Computed tomography (CT) shows the greatest proportion of the crude number and percentage; despite a slight decrease in percentage, it is still >80%. Among the combinations, CT alone and CT combined with ultrasonography showed the highest performance rate during the complete observational period. The proportion of all other combinations, which include other complex combinations except CT alone, CT plus ultrasonography, CT plus magnetic resonance imaging (MRI), and CT plus MRI plus ultrasonography, was 13.95% in 2007, but increased to 19.04% in 2014.

CONCLUSIONS

CT still plays a major role in preoperative imaging for renal masses, whereby CT alone and CT combined with ultrasonography account for a major proportion of the preoperative imaging patterns. The use of other imaging combinations, as well as renal biopsies, shows an increasing trend. Additional studies are needed to investigate whether this trend in preoperative imaging is related to the frequency rate of PN.

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.

Declining incidence of benign lesions among small renal masses treated with surgery: Effect of diagnostic tests for characterization

PURPOSE

We evaluated the changes in the incidence of benign lesions in surgically removed small renal masses (SRMs) and the effect of diagnostic tests for characterizing SRMs.

METHODS

We included 2,707 patients receiving surgery for SRMs (<4cm). Trends in the incidence of benign histology were evaluated according to the surgery year (period 1: 2001-2005, 2: 2006-2010, and 3: 2011-2015). Multivariable logistic regression analysis was performed to identify factors associated with benign lesions. Additionally, the number of surgeries prevented due to benign histological findings on renal mass biopsies (RMB) done on 206 patients with SRM during study period was evaluated.

RESULTS

Benign histology was identified in 192 (7.1%) patients. Incidence of benign histology was 9.7%, 7.0%, and 6.3% for period 1, 2 and 3, respectively. The uses of multiphase computed tomography and magnetic resonance imaging were more common in periods 2 and 3 than in period 1 (P<0.001). The use of RMB in period 3 was higher than in periods 1 and 2 (0.8 vs. 0.9 vs. 9.0%, P<0.001). In multivariable analysis, older age, male sex, larger tumor size, and recent surgery year (period 3 vs. 1, odds ratio = 0.62, P = 0.028) were independently associated with decreased odds of benign lesions. The number of prevented surgeries by performing RMB was 0, 10, and 39 in periods 1, 2, and 3, respectively.

CONCLUSIONS

Incidence of benign histology after surgery for SRMs declined during recent years, which might be associated with the recent increased use of RMB.

Angiomyolipoma of the Kidneys: Current Perspectives and Challenges in Diagnostic Imaging and Image-Guided Therapy

Angiomyolipomas (AML) are benign tumors of the kidneys frequently encountered in radiologic practice in large tertiary centers. In comparison to renal cell carcinomas (RCC), AML are seldom treated unless they are large, undergo malignant transformation or develop complications like acute hemorrhage. The common garden triphasic (classic) AML is an easy diagnosis, however, some variants lack macroscopic fat in which case the radiologic differentiation from RCC becomes challenging. Several imaging features, both qualitative and quantitative, have been described in differentiating the 2 entities. Although minimal fat AML is not entirely a radiologic diagnosis, the suspicion raised on imaging necessitates sampling and potentially avoids an unwanted surgery. Recently a new variant, epitheloid AML has been described which often has atypical imaging features and is at a higher risk for malignant transformation. Apart from the diagnosis, the radiologist also needs to convey information regarding nephrometric scores which help in surgical decision-making. Recently, more and more AMLs are managed with selective arterial embolization and percutaneous ablation, both of which are associated with less morbidity when compared to surgery. The purpose of this article is to review the imaging and pathologic features of classic AML as well as the differentiation of minimal fat AML from RCC. In addition, an overview of nephrometric scoring and image-guided interventions is also provided.