Percutaneous biopsy for risk stratification of renal masses

Radiomics and Artificial Intelligence: Renal Cell Carcinoma

There is a clinical need for accurate diagnosis and prognostication of kidney cancer using imaging. Radiomics and deep learning methods applied to imaging have shown promise in tasks such as tumor segmentation, classification, staging, and grading, as well as assessment of preoperative scores and correlation with tumor biomarkers. Artificial intelligence is also expected to play a significant role in advancing personalized medicine for the treatment of renal cell carcinoma.

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.

Role of Renal Biopsy in the Management of Renal Cancer: Concordance between Ultrasound/CT-Guided Biopsy Results and Definitive Pathology, Adverse Events, and Complication Rate

(1) Background: In the last decade, the number of detected renal cancer cases has increased, with the highest incidence in Western countries. Although renal biopsy is reported as a safe procedure, it is not adopted in all centres. As it is not possible to accurately distinguish benign tumours using imaging, this may lead to overtreatment. Most of the cancer detected on imaging is treated by surgery, radiofrequency ablation (RFA), or cryotherapy. (2) Methods: This was a single-centre retrospective study of 225 patients studied preoperatively with ultrasound (US)/CT-guided renal biopsy, with the aim of supporting clinical management. Decisions regarding the biopsy were based on either MDT indication or physician preference. US-guided renal biopsy was the first option for all patients; CT-guided biopsy was used when US-guided biopsy was not feasible. The efficacy of renal biopsy in terms of diagnostic performance and the concordance between biopsy results and definitive pathology were investigated. Additionally, adverse events related to the biopsy were recorded and analysed. Data collected throughout the study were analysed using binary logistic regression, Fisher's exact test, and Pearson's chi-square test to investigate possible correlations between post-procedural complications and the size of the lesion. (3) Results: Renal biopsy was not diagnostic in 23/225 (10.2%) patients. A CT-guided approach was necessary in 20/225 patients after failure of US-guided biopsy. The complication rate of renal biopsy was 4.8% overall-all Clavien grade I and without any serious sequelae. Interestingly, complications occurred in patients with very different sizes of renal cell carcinoma. No correlation between complications and anticoagulant/antiplatelet drugs was found. No seeding was reported among the patients who underwent partial/radical nephrectomy. (4) Conclusions: Renal biopsy was shown to be safe and effective, with a high concordance between biopsy results and definitive pathology and a low rate of complications. The use of a CT-guided approach whenever the US-guided approach failed improved the diagnostic performance of renal biopsy.

Surgical Management of Localized Disease and Small Renal Masses

The incidence of renal cancer has increased over the past several decades, but mortality has declined. This is thought to be related in part to earlier detection of renal masses which portend excellent 5-year survival rates. Management of small renal masses and localized disease include both nonsurgical and surgical options. The choice of intervention is ultimately based on comprehensive evaluation and shared decision-making. This article provides a comprehensive review of the current surgical management options for localized renal cancer.

Shape and texture-based radiomics signature on CT effectively discriminates benign from malignant renal masses

OBJECTIVES

Using a radiomics framework to quantitatively analyze tumor shape and texture features in three dimensions, we tested its ability to objectively and robustly distinguish between benign and malignant renal masses. We assessed the relative contributions of shape and texture metrics separately and together in the prediction model.

MATERIALS AND METHODS

Computed tomography (CT) images of 735 patients with 539 malignant and 196 benign masses were segmented in this retrospective study. Thirty-three shape and 760 texture metrics were calculated per tumor. Tumor classification models using shape, texture, and both metrics were built using random forest and AdaBoost with tenfold cross-validation. Sensitivity analyses on five sub-cohorts with respect to the acquisition phase were conducted. Additional sensitivity analyses after multiple imputation were also conducted. Model performance was assessed using AUC.

RESULTS

Random forest classifier showed shape metrics featuring within the top 10% performing metrics regardless of phase, attaining the highest variable importance in the corticomedullary phase. Convex hull perimeter ratio is a consistently high-performing shape feature. Shape metrics alone achieved an AUC ranging 0.64-0.68 across multiple classifiers, compared with 0.67-0.75 and 0.68-0.75 achieved by texture-only and combined models, respectively.

CONCLUSION

Shape metrics alone attain high prediction performance and high variable importance in the combined model, while being independent of the acquisition phase (unlike texture). Shape analysis therefore should not be overlooked in its potential to distinguish benign from malignant tumors, and future radiomics platforms powered by machine learning should harness both shape and texture metrics.

KEY POINTS

• Current radiomics research is heavily weighted towards texture analysis, but quantitative shape metrics should not be ignored in their potential to distinguish benign from malignant renal tumors. • Shape metrics alone can attain high prediction performance and demonstrate high variable importance in the combined shape and texture radiomics model. • Any future radiomics platform powered by machine learning should harness both shape and texture metrics, especially since tumor shape (unlike texture) is independent of the acquisition phase and more robust from the imaging variations.

Imaging guided percutaneous renal biopsy: do it or not?

Since its first reported application, renal biopsy became an important part of the diagnostic algorithm, considered advantages and risks, to better manage therapeutic options. The biopsy can be performed with different techniques (open, laparoscopic, transjugular, transurethral and percutaneous). Currently, the percutaneous approach is the modality of choice. Percutaneous biopsy can be performed under CT or US guidance, but critical benefits and disadvantages have to be considered. Core needle biopsy is usually preferred to fine-needle aspiration because of the sample quality, usually obtaining multiple cores, especially in heterogeneous tumors. Principal complications are hematuria (1-10%), perinephric hematoma (10-90%), pneumothorax (0,6%), clinically significant pain (1,2%).

Percutaneous renal biopsy: approach, diagnostic accuracy and risks

PURPOSE OF REVIEW

This article provides a review of recent advances and issues regarding the controversial topic of renal mass biopsy (RMB). The purpose of this review is to provide an update on the current status of renal biopsy based on recently published literature. Here, we particularly focus on articles that have been published within the last 12 months.

RECENT FINDINGS

The main topics covered in this review are the approach, diagnostic accuracy and risks related to RMB.

SUMMARY

Current literature suggests that improvements in both technique and technological advancements of RMB have led to greater diagnostic accuracy and low risks to the patient. Newer technologies are leading toward innovative and harmless ways to diagnose kidney cancer, including liquid and image-based biopsy. However, it appears that the question of whether or not to instate renal biopsy as standard clinical practice has remained a highly debated controversy.

A young female case of primary renal carcinoid tumor mimicking fat-poor angiomyolipoma

Renal mass biopsy is useful for the pathological diagnosis of a small renal mass difficult to distinguish fat-poor angiomyolipoma from renal cell carcinoma radiologically. Here, we report a young female case of a small renal mass suspected as fat-poor angiomyolipoma in imaging studies. The patient received a renal mass biopsy to obtain the correct pathological information. Unexpectedly, the pathological diagnosis was neuroendocrine tumor. She, finally, underwent a right radical nephrectomy as a curative treatment. This case indicates that the radiological findings of primary renal carcinoid tumor can be similar to those of fat-poor angiomyolipoma.

The kidney cancer research priority-setting partnership: Identifying the top 10 research priorities as defined by patients, caregivers, and expert clinicians

It is critically important to define disease-specific research priorities to better allocate limited resources. There is growing recognition of the value of involving patients and caregivers, as well as expert clinicians in this process. To our knowledge, this has not been done this way for kidney cancer. Using the transparent and inclusive process established by the James Lind Alliance, the Kidney Cancer Research Network of Canada (KCRNC) sponsored a collaborative consensus-based priority-setting partnership (PSP) to identify research priorities in the management of kidney cancer. The final result was identification of 10 research priorities for kidney cancer, which are discussed in the context of current initiatives and gaps in knowledge. This process provided a systematic and effective way to collaboratively establish research priorities with patients, caregivers, and clinicians, and provides a valuable resource for researchers and funding agencies.

Identification of clear cell renal cell carcinoma and oncocytoma using a three-gene promoter methylation panel

BACKGROUND

Promoter methylation has emerged as a promising class of epigenetic biomarkers for diagnosis and prognosis of renal cell tumors (RCTs). Although differential gene promoter methylation patterns have been reported for the major subtypes (clear cell, papillary and chromophobe renal cell carcinoma, and oncocytoma), validation of diagnostic performance in independent series have been seldom performed. Herein, we aimed at assessing the diagnostic performance of genes previously shown to be hypermethylated in RCTs in different clinical settings.

METHODS

Promoter methylation levels of HOXA9 and OXR1 were assessed by quantitative methylation specific PCR. ROC curves were generated for OXR1, OXR1 combined with MST1R and HOXA9. Sensitivity, specificity, positive predictive value, negative predictive value and accuracy were computed, maximizing specificity. Methylation levels were also correlated with clinical and pathological relevant parameters.

RESULTS

HOXA9 and OXR1 promoter methylation was disclosed in 73 and 87% of RCTs, respectively. A two-gene methylation panel comprising OXR1 and MST1R identified malignancy with 98% sensitivity and 100% specificity, and clear cell renal cell carcinoma with 90% sensitivity and 98% specificity. HOXA9 promoter methylation allowed for discrimination between oncocytoma and both papillary and chromophobe renal cell carcinoma but only with 77% sensitivity and 73% specificity. Significantly higher OXR1 promoter methylation levels (p = 0.005) were associated with high nuclear grade in ccRCC.

CONCLUSIONS

A panel including OXR1 and MST1R promoter methylation allows specific and sensitive identification of renal cell tumors, and, especially, of clear cell renal cell carcinoma. Moreover, higher OXR1 promoter methylation levels associate with clear cell renal cell carcinoma nuclear grade, a surrogate for tumor aggressiveness. Thus, gene promoter methylation analysis might a useful ancillary tool in diagnostic management of renal masses.

Aorta-Lesion-Attenuation-Difference (ALAD) on contrast-enhanced CT: a potential imaging biomarker for differentiating malignant from benign oncocytic neoplasms

OBJECTIVE

To evaluate whether the Aorta-Lesion-Attenuation-Difference on contrast-enhanced CT can aid in the differentiation of malignant and benign oncocytic renal neoplasms.

MATERIALS AND METHODS

Two independent cohorts-an initial (biopsy) dataset and a validation (surgical) dataset-with oncocytomas and chromophobe renal cell carcinomas (chRCC) were included in this IRB-approved retrospective study. A region of interest was placed on the renal mass and abdominal aorta on the same CT image slice to calculate an Aorta-Lesion-Attenuation-Difference (ALAD). ROC curves were plotted for different enhancement phases, and diagnostic performance of ALAD for differentiating chRCC from oncocytomas was calculated.

RESULTS

Seventy-nine renal masses (56 oncocytomas, 23 chRCC) were analyzed in the initial (biopsy) dataset. Thirty-six renal masses (16 oncocytomas, 20 chRCC) were reviewed in the validation (surgical) cohort. ALAD showed a statistically significant difference between oncocytomas and chromophobes during the nephrographic phase (p < 0.001), early excretory phase (p < 0.001), and excretory phase (p = 0.029). The area under the ROC curve for the nephrographic phase was 1.00 (95% CI: 1.00-1.00) for the biopsy dataset and showed the narrowest confidence interval. At a threshold value of 25.5 HU, sensitivity was 100 (82.2%-100%) and specificity was 81.5 (61.9%-93.7%). When tested on the validation dataset on measurements made by an independent reader, the AUROC was 0.93 (95% CI: 0.84-1.00) with a sensitivity of 100 (80.0%-100%) and a specificity of 87.5 (60.4%-97.8%).

CONCLUSIONS

Nephrographic phase ALAD has potential to differentiate benign and malignant oncocytic renal neoplasms on contrast-enhanced CT if histologic evaluation on biopsy is indeterminate.

Current Role of Renal Biopsy in Urologic Practice

Most small renal masses (SRMs) are indolent. In fact, only approximately 80% of SRMs are malignant. Furthermore, SRMs are commonly detected in elderly and comorbid patients. Therefore, opportunities for better care intensity calibration exist. Renal mass biopsy (RMB), when appropriately used, is a valuable clinical tool to help with critical clinical decision-making in patients with SRM. This article summarizes the role of modern RMB in helping gauge care for patients with SRM.

The independent oncological role for cytoreductive nephrectomy in metastatic renal cell carcinoma: Prognostic features in the era of targeted therapies

OBJECTIVES

To describe the effects of cytoreductive nephrectomy (CN) on the natural course of metastatic renal cell carcinoma (mRCC). CN appears to stabilize metastatic lesions in mRCC in a subgroup of patients and we hypothesize that systemic treatment might be deferred in these patients with stable disease after CN.

SUBJECTS AND METHODS

Overall, 45 patients with mRCC who underwent CN and subsequent oncologic follow-up were included in this retrospective, single-center analysis. After CN, patients were followed at least every 3 months with clinical evaluation, contrast-enhanced computerized tomography scan of chest and abdomen, with additional imaging if needed. At 3 months, patients were radiographically evaluated and categorized into nonresponders (death or progression) or responders (stable disease or remission). Kaplan-Meier and Cox proportional hazards regression statistics were used to describe prognostic factors for overall survival (OS) and systemic therapy-free survival (STFS).

RESULTS

Median OS was 31(3-121) months. Further, 24 (53.3%) and 21 (46.7%) patients were classified as responders and nonresponders at 3 months, respectively. Responders had a significant better 2-year OS compared with nonresponders (81.7% vs. 26.5%, P = 0.005). Responders also had a better 2-year STFS (40.3% vs. 6.3%, P = 0.005). On Cox regression analysis, worse OS was found to be associated with low preoperative hemoglobin levels, the absence of postoperative radiographical response, and the presence of non-clear cell pathology. The presence of postoperative radiographical response, normal preoperative lactate dehydrogenase levels, the presence of a single metastasis, and performing metastasis-directed therapy was found to be associated with a longer systemic therapy-free period.

CONCLUSION

A beneficial oncologic response is observed in approximately half of the patients undergoing CN. Absence of radiographic progression at 3 months is an important marker for OS and STFS. Therefore, systemic treatment might be postponed in selected patients.

Effect of Tumor Complexity and Technique on Efficacy and Complications after Percutaneous Microwave Ablation of Stage T1a Renal Cell Carcinoma: A Single-Center, Retrospective Study

Purpose To evaluate the effects of tumor complexity and technique on early and midterm oncologic efficacy and rate of complications for 100 consecutive biopsy-proved stage T1a renal cell carcinomas (RCCs) treated with percutaneous microwave ablation. Materials and Methods This HIPAA-compliant, single-center retrospective study was approved by the institutional review board. The requirement to obtain informed consent was waived. Ninety-six consecutive patients (68 men, 28 women; mean age, 66 years ± 9.4) with 100 stage T1a N0M0 biopsy-proved RCCs (median diameter, 2.6 cm ± 0.8) underwent percutaneous microwave ablation between March 2011 and June 2015. Patient and procedural data were collected, including body mass index, comorbidities, tumor histologic characteristics and grade, RENAL nephrometry score, number of antennas, generator power, and duration of ablation. Technical success, local tumor progression, and presence of complications were assessed at immediate and follow-up imaging. The Kaplan-Meier method was used for survival analyses. Results Technical success was achieved for all 100 tumors (100%), including 47 moderately and five highly complex RCCs. Median clinical and imaging follow-up was 17 months (range, 0-48 months) and 15 months (range, 0-44 months), respectively. No change in estimated glomerular filtration rate was noted after the procedure (P = .49). There were three (3%) procedure-related complications and six (6%) delayed complications, all urinomas. One case of local tumor progression (1%) was identified 25 months after the procedure. Three-year local progression-free survival, cancer-specific survival, and overall survival were 88% (95% confidence interval: 0.52%, 0.97%), 100% (95% confidence interval: 1.0%, 1.0%), and 91% (95% confidence interval: 0.51%, 0.99%), respectively. Conclusion Percutaneous microwave ablation is an effective and safe treatment option for stage T1a RCC, regardless of tumor complexity. Long-term follow-up is needed to establish durable oncologic efficacy and survival relative to competing ablation modalities and surgery. ^© RSNA, 2017.

Identification of aberrant tRNA-halves expression patterns in clear cell renal cell carcinoma

Small non-coding RNAs (sncRNA; <200 nt) regulate various cellular processes and modify gene expression. Under nutritional, biological or physiochemical stress some mature sncRNAs (e.g. tRNAs) are cleaved into halves (30–50 nt) and smaller fragments (18–22 nt); the significance and functional role of these tRNA fragments is unknown, but their existence has been linked to carcinogenesis. We used small RNA sequencing to determine the expression of sncRNAs. Subsequently the findings were validated for miR-122-5p, miR-142-3p and 5'tRNA4-Val-AAC using qPCR. We identified differential expression of 132 miRNAs (upregulated: 61, downregulated: 71) and 32 tRNAs (upregulated: 13, downregulated: 19). Read length analysis showed that miRNAs mapped in the 20–24 nt fraction, whereas tRNA reads mapped in the 30–36 nt fraction instead the expected size of 73–95 nt thereby indicating cleavage of tRNAs. Overexpression of miR-122-5p and miR-142-3p as well as downregulation of 5'tRNA4-Val-AAC was validated in an independent cohort of 118 ccRCC and 74 normal renal tissues. Furthermore, staging and grading was inversely correlated with the 5'tRNA4-Val-AAC expression. Serum levels of miR-122-5p, miR-142-3p and 5'tRNA4-Val-AAC did not differ in ccRCC and control subjects. In conclusion, 5′ cleavage of tRNAs occurs in ccRCC, but the exact functional implication of tRNA-halve deregulation remains to be clarified.

Percutaneous biopsy in large, locally advanced or metastatic renal tumors

INTRODUCTION

The role of percutaneous biopsy to characterize large, locally advanced and metastatic primary renal tumors has not been well described. The goal of this article is to describe the potential advantages of biopsy for preoperative evaluation of patients with large renal tumors and advanced disease.

METHODS

Literature was reviewed for percutaneous biopsy and for locally advanced and metastatic renal tumors.

RESULTS

Multiple studies have confirmed that percutaneous biopsy is safe, and the cost is minimal relative to the cost of surgical operation. Biopsy of large masses should obtain multiple core samples from several sites with tumors to decrease error from sampling heterogeneous tumors.

CONCLUSIONS

Potential advantages of biopsy for large renal masses include identification of patients for retroperitoneal lymph node dissection who may have occult lymph node metastasis. In patients with metastatic renal cell carcinoma, biopsy characterizes tumors for patients who may not benefit from cytoreductive surgical operation. The role of biopsy is likely to expand in the future with the development of advanced molecular tools for risk stratification.

Tumor Seeding With Renal Cell Carcinoma After Renal Biopsy

Tumor seeding following biopsy of renal cell carcinoma is extremely rare with an incidence of 1:10.000. In this paper two cases with multiple recurrent RRC metastasis in the biopsy tract following biopsy of renal tumor is presented and the current literature is shortly discussed.

Percutaneous biopsy facilitates modern treatment of renal masses

Contemporary approaches to cancer therapy have moved away from a one-size-fits-all model. Precision treatments are based on patients and their individual tumor characteristics. In general, incidental renal masses fall into three categories: aggressive cancers, indolent cancers, and benign tumors. Treatments may include surgery, thermal ablation, or observation. Choosing the best treatment based solely on radiologic information is uninformed and unnecessary, and may lead to overtreatment of benign tumors or inappropriate treatment of aggressive tumors. Percutaneous biopsy is a safe and effective tool that provides prognostic information about unknown masses to guide treatment decision making. The first step for improving personalized treatments for small renal masses is clear: increase utilization of pretreatment renal mass biopsy.

Percutaneous image-guided cryoablation of small renal masses

Renal cell carcinoma is a common malignancy with increasing incidence due to the incidental detection of non-symptomatic small renal masses on imaging. Management of these small tumors has evolved toward minimally invasive nephron-sparing techniques which include partial nephrectomy and image-guided ablation. Cryoablation and radiofrequency ablation are the most utilized ablation modalities with the former more suited for larger and central renal masses due to intra-procedural visualization of the ablation zone and reduced pelvicalyceal injury. In this article, we review the epidemiology and natural history of renal cell carcinoma, the role of biopsy, and the management options available-surgery, image-guided ablation, and active surveillance-with a focus on cryoablation. The clinical outcomes of the longer term maturing cryoablation data are discussed with reference to partial nephrectomy and radiofrequency ablation. Image-guided ablation has often been the management choice in patients deemed unfit for surgery; however, growing evidence from published series demonstrates image-guided ablation as a sound alternative treatment with equivalent oncological outcomes and minimal patient impact.