Growth Rates of Genetically Defined Renal Tumors: Implications for Active Surveillance and Intervention

CT-derived radiomics predict the growth rate of renal tumours in von Hippel-Lindau syndrome

AIM

To predict renal tumour growth patterns in von Hippel-Lindau syndrome by utilising radiomic features to assist in developing personalised surveillance plans leading to better patient outcomes.

MATERIALS AND METHODS

The study evaluated 78 renal tumours in 55 patients with histopathologically-confirmed clear cell renal cell carcinomas (ccRCCs), which were segmented and radiomics were extracted. Volumetric doubling time (VDT) classified the tumours into fast-growing (VDT <365 days) or slow-growing (VDT ≥365 days). Volumetric and diametric growth analyses were compared between the groups. Multiple logistic regression and random forest classifiers were used to select the best features and models based on their correlation and predictability of VDT.

RESULTS

Fifty-five patients (mean age 42.2 ± 12.2 years, 27 men) with a mean time difference of 3.8 ± 2 years between the baseline and preoperative scans were studied. Twenty-five tumours were fast-growing (low VDT, i.e., <365 days), and 53 tumours were slow-growing (high VDT, i.e., ≥365 days). The median volumetric and diametric growth rates were 1.71 cm3/year and 0.31 cm/year. The best feature using univariate analysis was wavelet-HLL_glcm_ldmn (area under the receiver operating characteristic [ROC] curve [AUC] of 0.80, p<0.0001), and with the random forest classifier, it was log-sigma-0-5-mm-3D_glszm_ZonePercentage (AUC: 79). The AUC of the ROC curves using multiple logistic regression was 0.74, and with the random forest classifier was 0.73.

CONCLUSION

Radiomic features correlated with VDT and were able to predict the growth pattern of renal tumours in patients with VHL syndrome.

Hereditary Renal Cancer Syndromes

Familial kidney tumors represent a rare variety of hereditary cancer syndromes, although systematic gene sequencing studies revealed that as many as 5% of renal cell carcinomas (RCCs) are associated with germline pathogenic variants (PVs). Most instances of RCC predisposition are attributed to the loss-of-function mutations in tumor suppressor genes, which drive the malignant progression via somatic inactivation of the remaining allele. These syndromes almost always have extrarenal manifestations, for example, von Hippel-Lindau (VHL) disease, fumarate hydratase tumor predisposition syndrome (FHTPS), Birt-Hogg-Dubé (BHD) syndrome, tuberous sclerosis (TS), etc. In contrast to the above conditions, hereditary papillary renal cell carcinoma syndrome (HPRCC) is caused by activating mutations in the MET oncogene and affects only the kidneys. Recent years have been characterized by remarkable progress in the development of targeted therapies for hereditary RCCs. The HIF2aplha inhibitor belzutifan demonstrated high clinical efficacy towards VHL-associated RCCs. mTOR downregulation provides significant benefits to patients with tuberous sclerosis. MET inhibitors hold promise for the treatment of HPRCC. Systematic gene sequencing studies have the potential to identify novel RCC-predisposing genes, especially when applied to yet unstudied populations.

The kidney imaging surveillance scoring system (KISSS): using qualitative MRI features to predict growth rate of renal tumors in patients with von-Hippel Lindau (VHL) syndrome

OBJECTIVE

To determine the reliability of an MRI-based qualitative kidney imaging surveillance scoring system (KISSS) and assess which imaging features predict growth rate (GR) of renal tumors in patients with VHL.

MATERIALS AND METHODS

We identified 55 patients with VHL with 128 renal tumors who underwent intervention from 2015 to 2020 at the National Cancer Institute. All patients had 2 preoperative MRIs at least 3 months apart. Two fellowship-trained radiologists scored each tumor on location and MR-sequence-specific imaging parameters from the earlier MRI. Weighted kappa was used to determine the degree of agreement between radiologists for each parameter. GR was calculated as the difference in maximum tumor dimension over time (cm/year). Differences in mean growth rate (MGR) within categories of each imaging variable were assessed by ANOVA.

RESULTS

Apart from tumor margin and renal sinus, reliability was at least moderate (K > 0.40) for imaging parameters. Median initial tumor size was 2.1 cm, with average follow-up of 1.2 years. Tumor MGR was 0.42 cm/year. T2 hypointense, mixed/predominantly solid, and high restricted diffusion tumors grew faster. When comparing different combinations of these variables, the model with the lowest mean error among both radiologists utilized only solid/cystic and restricted diffusion features.

CONCLUSIONS

We demonstrate a novel MR-based scoring system (KISSS) that has good precision with minimal training and can be applied to other qualitative radiology studies. A subset of imaging variables (T2 intensity; restricted diffusion; and solid/cystic) were independently associated with growth rate in VHL renal tumors, with the combination of the latter two most optimal. Additional validation, including in sporadic RCC population, is warranted.

Preoperative Renal Parenchyma Volume as a Predictor of Kidney Function Following Nephrectomy of Complex Renal Masses

Background

The von Hippel-Lindau disease (VHL) is a hereditary cancer syndrome with multifocal, bilateral cysts and solid tumors of the kidney. Surgical management may include multiple extirpative surgeries, which ultimately results in parenchymal volume loss and subsequent renal function decline. Recent studies have utilized parenchyma volume as an estimate of renal function prior to surgery for renal cell carcinoma; however, it is not yet validated for surgically altered kidneys with multifocal masses and complex cysts such as are present in VHL.

Objective

We sought to validate a magnetic resonance imaging (MRI)-based volumetric analysis with mercaptoacetyltriglycine (MAG-3) renogram and postoperative renal function.

Design setting and participants

We identified patients undergoing renal surgery at the National Cancer Institute from 2015 to 2020 with preoperative MRI. Renal tumors, cysts, and parenchyma of the operated kidney were segmented manually using ITK-SNAP software.

Outcome measurements and statistical analysis

Serum creatinine and urinalysis were assessed preoperatively, and at 3- and 12-mo follow-up time points. Estimated glomerular filtration rate (eGFR) was calculated using serum creatinine-based CKD-EPI 2021 equation. A statistical analysis was conducted on R Studio version 4.1.1.

Results and limitations

Preoperative MRI scans of 113 VHL patients (56% male, median age 48 yr) were evaluated between 2015 and 2021. Twelve (10.6%) patients had a solitary kidney at the time of surgery; 59 (52%) patients had at least one previous partial nephrectomy on the renal unit. Patients had a median of three (interquartile range [IQR]: 2-5) tumors and five (IQR: 0-13) cysts per kidney on imaging. The median preoperative GFR was 70 ml/min/1.73 m2 (IQR: 58-89). Preoperative split renal function derived from MAG-3 studies and MRI split renal volume were significantly correlated (r = 0.848, p < 0.001). On the multivariable analysis, total preoperative parenchymal volume, solitary kidney, and preoperative eGFR were significant independent predictors of 12-mo eGFR. When only considering patients with two kidneys undergoing partial nephrectomy, preoperative parenchymal volume and eGFR remained significant predictors of 12-mo eGFR.

Conclusions

A parenchyma volume analysis on preoperative MRI correlates well with renogram split function and can predict long-term renal function with added benefit of anatomic detail and ease of application.

Patient summary

Prior to kidney surgery, it is important to understand the contribution of each kidney to overall kidney function. Nuclear medicine scans are currently used to measure split kidney function. We demonstrated that kidney volumes on preoperative magnetic resonance imaging can also be used to estimate split kidney function before surgery, while also providing essential details of tumor and kidney anatomy.

Clinical practice guidelines for the diagnosis and surveillance of BAP1 tumour predisposition syndrome

BRCA1-associated protein-1 (BAP1) is a recognised tumour suppressor gene. Germline BAP1 pathogenic/likely pathogenic variants are associated with predisposition to multiple tumours, including uveal melanoma, malignant pleural and peritoneal mesothelioma, renal cell carcinoma and specific non-malignant neoplasms of the skin, as part of the autosomal dominant BAP1-tumour predisposition syndrome. The overall lifetime risk for BAP1 carriers to develop at least one BAP1-associated tumour is up to 85%, although due to ascertainment bias, current estimates of risk are likely to be overestimated. As for many rare cancer predisposition syndromes, there is limited scientific evidence to support the utility of surveillance and, therefore, management recommendations for BAP1 carriers are based on expert opinion. To date, European recommendations for BAP1 carriers have not been published but are necessary due to the emerging phenotype of this recently described syndrome and increased identification of BAP1 carriers via large gene panels or tumour sequencing. To address this, the Clinical Guideline Working Group of the CanGene-CanVar project in the United Kingdom invited European collaborators to collaborate to develop guidelines to harmonize surveillance programmes within Europe. Recommendations with respect to BAP1 testing and surveillance were achieved following literature review and Delphi survey completed by a core group and an extended expert group of 34 European specialists including Geneticists, Ophthalmologists, Oncologists, Dermatologists and Pathologists. It is recognised that these largely evidence-based but pragmatic recommendations will evolve over time as further data from research collaborations informs the phenotypic spectrum and surveillance outcomes.

Building a Roadmap for Surveillance of Renal Masses Using a Modified Delphi Method to Help Achieve Consensus

OBJECTIVE

To establish a consensus for initial evaluation and follow-up of patients on active surveillance (AS) for T1 renal masses (T1RM).

METHODS

A modified Delphi method was used to gather information about AS of T1RM, with a focus on patient selection, timing/type of imaging modality, and triggers for intervention. A consensus panel of Michigan Urological Surgery Improvement Collaborative-affiliated urologists who routinely manage renal masses was formed. Areas of consensus (defined >80% agreement) about T1RM AS were established iteratively via 3 rounds of online questionnaires.

RESULTS

Twenty-six Michigan Urological Surgery Improvement Collaborative urologists formed the panel. Consensus was achieved for 321/587 scenarios (54.7%) administered through 124 questions. Life expectancy, age, comorbidity, and renal function were most important for patient selection, with life expectancy ranking first. All tumors <3 cm and all patients with life expectancy <1 year were considered appropriate for AS. Appropriateness also increased with elevated perioperative risk, increasing tumor complexity, and/or declining renal function. Consensus was for multiphasic axial imaging initially (contrast CT for GFR >60 or MRI for GFR >30) with first repeat imaging at 3-6 months and subsequent imaging timing determined by tumor size. Consensus was for chest imaging for tumors >3 cm initially and >5 cm at follow up. Renal biopsy was not felt to be a requirement for entering AS, but useful in several scenarios. Consensus indicated rapid tumor growth as an appropriate trigger for intervention.

CONCLUSION

Our consensus panel was able to achieve areas of consensus to help define a clinically useful and specific roadmap for AS of T1RM and areas for further discussion where consensus was not achieved.

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.

Adjuvant Therapy for Renal Cell Carcinoma: End Points, Outcomes, and Risk Assessments

PURPOSE

Targeted tyrosine kinase inhibitors (TKIs) and immune-checkpoint inhibitors (ICIs) revolutionized the treatment of metastatic renal cell carcinoma (RCC). Efforts to translate these therapies into the adjuvant setting for local and locoregional RCC have been pursued over the past decade. We sought to provide an updated review of the literature regarding adjuvant therapy in RCC, as well as an analysis of patient characteristics that may portend the most favorable responses.

MATERIALS AND METHODS

Using PubMed, Google Scholar, and Wiley Online Library, we reviewed articles between 2000 and 2022. Search terms included "tyrosine kinase inhibitors," "adjuvant," "immunotherapy," and "renal cell carcinoma." The articles included were original and published in English. Information on clinical trials was collected from ClinicalTrials.gov, accessed in June 2022.

RESULTS

Landmark trials investigating adjuvant vascular endothelial growth factor (VEGF) inhibitors produced conflicting results, with only a single trial of sunitinib (S-TRAC) resulting in US Food and Drug Administration-approval on the basis of a slightly prolonged progression-free survival (PFS). Subsequent meta-analyses failed to show a benefit for adjuvant VEGF inhibitors. Several trials evaluating ICIs are currently ongoing, with pembrolizumab (KEYNOTE-564) earning US Food and Drug Administration-approval for a prolonged PFS, although overall survival data are not yet mature. Preliminary results from other adjuvant ICI trials have been conflicting.

CONCLUSION

There remains a lack of clear benefit for the use of adjuvant VEGF inhibitors in local and locoregional RCC. Adjuvant ICI investigations are ongoing, with promising results from KEYNOTE-564. It remains to be seen if PFS is an adequate surrogate end point for overall survival. Selection of patients at greatest risk for recurrence, and identification of those at greatest risk of rare but serious adverse events, may improve outcomes.

Tumorigenesis Mechanisms Found in Hereditary Renal Cell Carcinoma: A Review

Renal cell carcinoma is a heterogenous cancer composed of an increasing number of unique subtypes each with their own cellular and tumor behavior. The study of hereditary renal cell carcinoma, which composes just 5% of all types of tumor cases, has allowed for the elucidation of subtype-specific tumorigenesis mechanisms that can also be applied to their sporadic counterparts. This review will focus on the major forms of hereditary renal cell carcinoma and the genetic alterations contributing to their tumorigenesis, including von Hippel Lindau syndrome, Hereditary Papillary Renal Cell Carcinoma, Succinate Dehydrogenase-Deficient Renal Cell Carcinoma, Hereditary Leiomyomatosis and Renal Cell Carcinoma, BRCA Associated Protein 1 Tumor Predisposition Syndrome, Tuberous Sclerosis, Birt-Hogg-Dubé Syndrome and Translocation RCC. The mechanisms for tumorigenesis described in this review are beginning to be exploited via the utilization of novel targets to treat renal cell carcinoma in a subtype-specific fashion.

An MRI-based radiomics model to predict clear cell renal cell carcinoma growth rate classes in patients with von Hippel-Lindau syndrome

PURPOSE

Upfront knowledge of tumor growth rates of clear cell renal cell carcinoma in von Hippel-Lindau syndrome (VHL) patients can allow for a more personalized approach to either surveillance imaging frequency or surgical planning. In this study, we implement a machine learning algorithm utilizing radiomic features of renal tumors identified on baseline magnetic resonance imaging (MRI) in VHL patients to predict the volumetric growth rate category of these tumors.

MATERIALS AND METHODS

A total of 73 VHL patients with 173 pathologically confirmed Clear Cell Renal Cell Carcinoma (ccRCCs) underwent MRI at least at two different time points between 2015 and 2021. Each tumor was manually segmented in excretory phase contrast T1 weighed MRI and co-registered on pre-contrast, corticomedullary and nephrographic phases. Radiomic features and volumetric data from each tumor were extracted using the PyRadiomics library in Python (4544 total features). Tumor doubling time (DT) was calculated and patients were divided into two groups: DT <  = 1 year and DT > 1 year. Random forest classifier (RFC) was used to predict the DT category. To measure prediction performance, the cohort was randomly divided into 100 training and test sets (80% and 20%). Model performance was evaluated using area under curve of receiver operating characteristic curve (AUC-ROC), as well as accuracy, F1, precision and recall, reported as percentages with 95% confidence intervals (CIs).

RESULTS

The average age of patients was 47.2 ± 10.3 years. Mean interval between MRIs for each patient was 1.3 years. Tumors included in this study were categorized into 155 Grade 2; 16 Grade 3; and 2 Grade 4. Mean accuracy of RFC model was 79.0% [67.4-90.6] and mean AUC-ROC of 0.795 [0.608-0.988]. The accuracy for predicting DT classes was not different among the MRI sequences (P-value = 0.56).

CONCLUSION

Here we demonstrate the utility of machine learning in accurately predicting the renal tumor growth rate category of VHL patients based on radiomic features extracted from different T1-weighted pre- and post-contrast MRI sequences.

Von Hippel-Lindau disease-associated renal cell carcinoma: a call to action

PURPOSE OF REVIEW

While the molecular and genetic bases of Von Hippel-Lindau (VHL) disease have been extensively investigated, limited evidence is available to guide diagnosis, local or systemic therapy, and follow-up. The aim of the current review is to summarize the ongoing trials both in preclinical and clinical setting regarding VHL disease management.

RECENT FINDINGS

Although genotype/phenotype correlations have been described, there is considerable inter and intra-familiar heterogeneity in VHL disease. Genetic anticipation has been reported in VHL disease. From a clinical point of view, expert-opinion-based protocols suggest testing those patients with any blood relative of an individual diagnosed with VHL disease, those with at least 1 or more suggestive neoplasms or patients presenting with clear cell renal cell carcinoma (ccRCC) diagnosed at a less than 40 years old, and/or multiple ccRCC. Clinical research is focused on safety and efficacy of systemic agents for patients with VHL-related ccRCC, with the aim to possibly preserve kidney function and improve patient survival.

SUMMARY

To date, preclinical and clinical research on the topic is scarce and clinical guidelines are not supported by strong validation studies.

A 17-Gene Expression Signature for Early Identification of Poor Prognosis in Clear Cell Renal Cell Carcinoma

The Identification of reliable Biomarkers able to predict the outcome after nephrectomy of patients with clear cell renal cell carcinoma (ccRCC) is an unmet need. The gene expression analysis in tumor tissues represents a promising tool for better stratification of ccRCC subtypes and patients' evaluation.

METHODS

In our study we retrospectively analyzed using Next-Generation expression analysis (NanoString), the expression of a gene panel in tumor tissue from 46 consecutive patients treated with nephrectomy for non-metastatic ccRCC at two Italian Oncological Centres. Significant differences in expression levels of selected genes was sought. Additionally, we performed a univariate and a multivariate analysis on overall survival according to Cox regression model.

RESULTS

A 17-gene expression signature of patients with a recurrence-free survival (RFS) < 1 year (unfavorable genomic signature (UGS)) and of patients with a RFS > 5 years (favorable genomic signature (FGS)) was identified and resulted in being significantly correlated with overall survival of the patients included in this analysis (HR 51.37, p < 0.0001).

CONCLUSIONS

The identified Genomic Signatures may serve as potential biomarkers for prognosis prediction of non-metastatic RCC and could drive both follow-up and treatment personalization in RCC management.

Germline BAP1 Mutation in a Family With Multi-Generational Meningioma With Rhabdoid Features: A Case Series and Literature Review

Meningioma is the most common primary brain tumor, and recurrence risk increases with increasing WHO Grade from I to III. Rhabdoid meningiomas are a subset of WHO Grade III tumors with rhabdoid cells, a high proliferation index, and other malignant features that follow an aggressive clinical course. Some meningiomas with rhabdoid features either only focally or without other malignant features are classified as lower grade yet still recur early. Recently, inactivating mutations in the tumor suppressor gene BAP1 have been associated with poorer prognosis in rhabdoid meningioma and meningioma with rhabdoid features, and germline mutations have been linked to a hereditary tumor predisposition syndrome (TPDS) predisposing patients primarily to melanoma and mesothelioma. We present the first report of a familial BAP1 inactivating mutation identified after multiple generations of a family presented with meningiomas with rhabdoid features instead of with previously described BAP1 loss-associated malignancies. A 24-year-old female presented with a Grade II meningioma with rhabdoid and papillary features treated with subtotal resection, adjuvant external beam radiation therapy, and salvage gamma knife radiosurgery six years later. Around that time, her mother presented with a meningioma with rhabdoid and papillary features managed with resection and adjuvant radiation therapy. Germline testing was positive for a pathogenic BAP1 mutation in both patients. Sequencing of both tumors demonstrated biallelic BAP1 inactivation via the combination of germline BAP1 mutation and either loss of heterozygosity or somatic mutation. No additional mutations implicated in oncogenesis were noted from either patient's germline or tumor sequencing, suggesting that the inactivation of BAP1 was responsible for pathogenesis. These cases demonstrate the importance of routine BAP1 tumor testing in meningioma with rhabdoid features regardless of grade, germline testing for patients with BAP1 inactivated tumors, and tailored cancer screening in this population.

Radiomics to better characterize small renal masses

PURPOSE

Radiomics is a specific field of medical research that uses programmable recognition tools to extract objective information from standard images to combine with clinical data, with the aim of improving diagnostic, prognostic, and predictive accuracy beyond standard visual interpretation. We performed a narrative review of radiomic applications that may support improved characterization of small renal masses (SRM). The main focus of the review was to identify and discuss methods which may accurately differentiate benign from malignant renal masses, specifically between renal cell carcinoma (RCC) subtypes and from angiomyolipoma without visible fat (fat-poor AML) and oncocytoma. Furthermore, prediction of grade, sarcomatoid features, and gene mutations would be of importance in terms of potential clinical utility in prognostic stratification and selecting personalised patient management strategies.

METHODS

A detailed search of original articles was performed using the PubMed-MEDLINE database until 20 September 2020 to identify the English literature relevant to radiomics applications in renal tumour assessment. In total, 42 articles were included in the analysis in 3 main categories related to SRM: prediction of benign versus malignant SRM, subtypes, and nuclear grade, and other features of aggressiveness.

CONCLUSION

Overall, studies reported the superiority of radiomics over expert radiological assessment, but were mainly of retrospective design and therefore of low-quality evidence. However, it is clear that radiomics is an attractive modality that has the potential to improve the non-invasive diagnostic accuracy of SRM imaging and prediction of its natural behaviour. Further prospective validation studies of radiomics are needed to augment management algorithms of SRM.

Kidney cancer: from genes to therapy

Renal cell carcinoma incidence is rising worldwide with increasing subtype stratification by the World Health Organization. Each subtype has unique genetic alterations, cell biology changes and clinical findings. Such genetic alterations offer the potential for individualized therapeutic approaches that are rapidly progressing. This review highlights the most common subtypes of renal cell carcinoma, including both hereditary and sporadic forms, with a focus on genetic changes, clinical findings and ongoing clinical trials.

A 25 year perspective on the evolution and advances in an understanding of the biology, evaluation and treatment of kidney cancer

The diagnosis, evaluation and management of patients with renal cell carcinoma has transformed in the 21st century. Utilizing biological discoveries and technological advances, the field has moved from blunt surgical and largely ineffective medical treatments, to nuanced and fine-tuned approaches based on biology, extent of disease and patient preferences. In this review we will summarize the last 25 years of progress in kidney cancer.

Precision Surgery and Kidney Cancer: Knowledge of Genetic Alterations Influences Surgical Management

Renal cell carcinoma is a term that represents multiple different disease processes, each driven by different genetic alterations, with distinct histology, and biological potential which necessitates divergent management strategies. This review discusses the genetic alterations seen in several forms of hereditary kidney cancer and how that knowledge can dictate when and how to intervene with a focus on the surgical management of these tumors.

Long term outcomes for patients with von Hippel-Lindau and Pheochromocytoma: defining the role of active surveillance

INTRODUCTION

Patients with a confirmed germline mutation in the von Hippel-Lindau (VHL) tumor suppressor gene have been followed at the National Cancer Institute since the 1980s. In this study, we identify VHL patients with pheochromocytoma and long-term follow-up to determine the best candidates for active surveillance and surgical resection.

METHODS

A prospectively collected database of patients with a confirmed germline VHL mutation was reviewed to identify patients with a history of pheochromocytoma and at least 10 years of follow up. The presence of symptoms was assessed at the time of resection. Imaging data obtained at each clinic visit was reviewed to evaluate mass size and annual growth rate. Catecholamine data were reviewed to evaluate for data above the upper limit of the reference range. Masses that underwent imaging at least 3 months apart were considered in our surveillance cohort.

RESULTS

Median follow up was 16.7 years. There was a size-dependent increase in catecholamine production (P<0.05). For 36 masses on active surveillance, growth rate increased exponentially from 0.03 cm/y when masses were <1 cm to 0.32 cm/y when masses were greater than 2 cm. Approximately 1/3 of patients developed another pheochromocytoma after initial resection with a median time of 7.9 years. Partial adrenalectomy was associated with no metastatic events and a steroid-free rate of 97%.

CONCLUSION

Active surveillance is a safe strategy for management of VHL associated pheochromocytoma in masses less than 2 cm.

Microsimulation Model for Evaluating the Cost-Effectiveness of Surveillance in BAP1 Pathogenic Variant Carriers

PURPOSE

Pathogenic BAP1 germline variants cause a tumor-predisposition syndrome (BAP1-TPDS) linked to uveal melanoma, mesothelioma, cutaneous melanoma, and renal cell carcinoma. Surveillance of carriers of pathogenic BAP1 variants provides an opportunity for early tumor detection; however, there are no evidence-based guidelines for management of BAP1-TPDS, nor health economic evaluation; this study aims to provide this evidence.

METHODS

We created a Markov microsimulation health state transition model of BAP1 germline carriers to predict if active surveillance for the four main tumors influences survival and improves associated economic costs with a time horizon of 100 years from the perspective of the healthcare system (N = 10,000). Model inputs were derived from data published by the BAP1 Interest Group Consortium and other studies. Management and healthcare costs were extracted from Australian costing schedules (final figures converted to US dollars [USD]), and outcomes compared for individuals receiving surveillance with those in a nonsurveillance arm. Robustness was evaluated on 10,000 iterations of a 100-sample random sampling of the model output.

RESULTS

On average, surveillance of BAP1 carriers increased survival by 4.9 years at an additional cost of $6,197 USD for the healthcare system including surveillance costs ($1,265 USD per life year gained). The nonsurveillance arm had more diagnosed late tumors (62.8% v 10.7%) and a higher rate of BAP1-related deaths (50.2% v 35.4%; a 29.5% increase). The model was cost-effective under all sensitivity analyses. Our secondary robustness analysis estimated that 99.86% of 100-sample iterations were cost-effective and 19.67% of these were cost-saving.

CONCLUSION

It is recommended that carriers of BAP1 germline variants are identified and undertake active surveillance, as this model suggests that this could improve survival and be cost-effective for the healthcare system.

Mitochondrial DNA alterations underlie an irreversible shift to aerobic glycolysis in fumarate hydratase-deficient renal cancer

Understanding the mechanisms of the Warburg shift to aerobic glycolysis is critical to defining the metabolic basis of cancer. Hereditary leiomyomatosis and renal cell carcinoma (HLRCC) is an aggressive cancer characterized by biallelic inactivation of the gene encoding the Krebs cycle enzyme fumarate hydratase, an early shift to aerobic glycolysis, and rapid metastasis. We observed impairment of the mitochondrial respiratory chain in tumors from patients with HLRCC. Biochemical and transcriptomic analyses revealed that respiratory chain dysfunction in the tumors was due to loss of expression of mitochondrial DNA (mtDNA)-encoded subunits of respiratory chain complexes, caused by a marked decrease in mtDNA content and increased mtDNA mutations. We demonstrated that accumulation of fumarate in HLRCC tumors inactivated the core factors responsible for replication and proofreading of mtDNA, leading to loss of respiratory chain components, thereby promoting the shift to aerobic glycolysis and disease progression in this prototypic model of glucose-dependent human cancer.

Triggers for delayed intervention in patients with small renal masses undergoing active surveillance: a systematic review

INTRODUCTION

Patients with small renal masses (SRM) can be exposed to overdiagnosis and overtreatment. As such, active surveillance (AS) is recommended by all Guidelines for selected patients. However, it remains underutilized. One key reason is the lack of consensus on the factors prompting delayed intervention (DI). Herein we provide an updated overview of the triggers for DI in patients with SRMs initially undergoing AS.

EVIDENCE ACQUISITION

A systematic review of the English-language literature was performed according to the PRISMA statement recommendations using the MEDLINE, Cochrane Central Register of Controlled Trials and Web of Science databases.

EVIDENCE SYNTHESIS

Overall, 10 prospective studies including 1870 patients were included. Median patient age ranged between 64 and 75 years, while median tumor size between 1.7 cm to 2.3 cm. The proportion of cystic SRMs ranged from 0% to 30%. Baseline renal tumor biopsy was performed in 7-45.2% of patients. Among these, malignant histology was found in 28.5%-83.3% of cases. Overall, the median growth rate of SRMs ranged between 0.10 and 0.27 cm/year. The proportion of patients undergoing DI ranged between 7% and 44%, after a median AS period of 12-27 months. The most commonly performed type of DI was surgery. Of resected SRMs, 0% to 30% were benign. The actual triggers for DI were either tumor-related (renal mass growth, stage progression, development of local complications/symptoms) or patient-related (patient preference, improved medical conditions, or qualification for other surgical procedures). At a median follow-up of 21.7 - 57-6 months, the proportion of patients experiencing metastatic disease, cancer-specific and other-cause mortality was 0-3.1%, 0-4% and 0-45.6%, respectively.

CONCLUSIONS

The available evidence shows that both tumor-related and patient-related factors are ultimate triggers for DI in patients with SRMs undergoing AS. However, the level of evidence is still low and further research is needed to individualize AS strategies according to both tumor biology and patient-related characteristics and values.

Genetic Alterations in Renal Cancers: Identification of The Mechanisms Underlying Cancer Initiation and Progression and of Therapeutic Targets

Renal cell cancer (RCC) involves three most recurrent sporadic types: clear-cell RCC (70-75%, CCRCC), papillary RCCC (10-15%, PRCC), and chromophobe RCC (5%, CHRCC). Hereditary cases account for about 5% of all cases of RCC and are caused by germline pathogenic variants. Herein, we review how a better understanding of the molecular biology of RCCs has driven the inception of new diagnostic and therapeutic approaches. Genomic research has identified relevant genetic alterations associated with each RCC subtype. Molecular studies have clearly shown that CCRCC is universally initiated by Von Hippel Lindau (VHL) gene dysregulation, followed by different types of additional genetic events involving epigenetic regulatory genes, dictating disease progression, aggressiveness, and differential response to treatments. The understanding of the molecular mechanisms that underlie the development and progression of RCC has considerably expanded treatment options; genomic data might guide treatment options by enabling patients to be matched with therapeutics that specifically target the genetic alterations present in their tumors. These new targeted treatments have led to a moderate improvement of the survival of metastatic RCC patients. Ongoing studies based on the combination of immunotherapeutic agents (immune check inhibitors) with VEGF inhibitors are expected to further improve the survival of these patients.

Small Renal Mass Surveillance: Histology-specific Growth Rates in a Biopsy-characterized Cohort

BACKGROUND

Most reports of active surveillance (AS) of small renal masses (SRMs) lack biopsy confirmation, and therefore include benign tumors and different subtypes of renal cell carcinoma (RCC).

OBJECTIVE

We compared the growth rates and progression of different histologic subtypes of RCC SRMs (SRM^RCC) in the largest cohort of patients with biopsy-characterized SRMs on AS.

DESIGN, SETTING, AND PARTICIPANTS

Data from patients in a multicenter Canadian trial and a Princess Margaret cohort were combined to include 136 biopsy-proven SRM^RCC lesions managed by AS, with treatment deferred until progression or patient/surgeon decision.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Growth curves were estimated from serial tumor size measures. Tumor progression was defined by sustained size ≥4 cm or volume doubling within 1 yr.

RESULTS AND LIMITATIONS

Median follow-up for patients who remained on AS was 5.8 yr (interquartile range 3.4-7.5 yr). Clear cell RCC SRMs (SRM^ccRCC) grew faster than papillary type 1 SRMs (0.25 and 0.02 cm/yr on average, respectively, p =  0.0003). Overall, 60 SRM^RCC lesions progressed: 49 (82%) by rapid growth (volume doubling), seven (12%) increasing to ≥4 cm, and four (6.7%) by both criteria. Six patients developed metastases, and all were of clear cell RCC histology. Limitations include the use of different imaging modalities and a lack of central imaging review.

CONCLUSIONS

Tumor growth varies between histologic subtypes of SRM^RCC and among SRM^ccRCC, which likely reflects individual host and tumor biology. Without validated biomarkers that predict this variation, initial follow-up of histologically characterized SRMs can inform personalized treatment for patients on AS.

PATIENT SUMMARY

Many small kidney cancers are suitable for surveillance and can be monitored over time for change. We demonstrate that different types of kidney cancers grow at different rates and are at different risks of progression. These results may guide better personalized treatment.