Harnessing the Genomic Landscape of the Small Renal Mass to Guide Clinical Management

The evolving management of small renal masses

Small renal masses (SRMs) are a heterogeneous group of tumours with varying metastatic potential. The increasing use and improving quality of abdominal imaging have led to increasingly early diagnosis of incidental SRMs that are asymptomatic and organ confined. Despite improvements in imaging and the growing use of renal mass biopsy, diagnosis of malignancy before treatment remains challenging. Management of SRMs has shifted away from radical nephrectomy, with active surveillance and nephron-sparing surgery taking over as the primary modalities of treatment. The optimal treatment strategy for SRMs continues to evolve as factors affecting short-term and long-term outcomes in this patient cohort are elucidated through studies from prospective data registries. Evidence from rapidly evolving research in biomarkers, imaging modalities, and machine learning shows promise in improving understanding of the biology and management of this patient cohort.

Small Renal Masses: The Evolving Histologic, Imaging, and Genomic Landscapes

According to the American Cancer Society, it is currently estimated that approximately 81,800 new cases of kidney cancer will be diagnosed in the United States in 2023 [...].

Somatic mutations as preoperative predictors of metastases in patients with localized clear cell renal cell carcinoma - An exploratory analysis

OBJECTIVE

Recurrent genomic alterations in clear cell renal cell carcinoma (ccRCC) have been associated with treatment outcomes; however, current preoperative predictive models do not include known genetic predictors. We aimed to explore the value of common somatic mutations in the preoperative prediction of metastatic disease among patients treated for localized ccRCC.

MATERIALS AND METHODS

After obtaining institutional review board approval, data of 254 patients with localized ccRCC treated between 2005 and 2015 who underwent genetic sequencing was collected. The mutation status of VHL, PBRM1, SETD2, BAP1 and KDM5C were evaluated in the nephrectomy tumor specimen, which served as a proxy for biopsy mutation status. The Raj et al. preoperative nomogram was used to predict the 12-year metastatic free probability (MFP). The study outcome was MFP; the relationship between MFP and mutation status was evaluated with Cox-regression models adjusting for the preoperative nomogram variables (age, gender, incidental presentation, lymphadenopathy, necrosis, and size).

RESULTS

The study cohort included 188 males (74%) and 66 females (26%) with a median age of 58 years. VHL mutations were present in 152/254 patients (60%), PBRM1 in 91/254 (36%), SETD2 in 32/254 (13%), BAP1 in 19/254 (8%), and KDM5C in 19/254 (8%). Median follow-up for survivors was 8.1 years. Estimated 12-year MFP was 70% (95% CI: 63%-75%). On univariable analysis SETD2 (HR: 3.30), BAP1 (HR: 2.44) and PBRM1 (HR: 1.78) were significantly associated with a higher risk of metastases. After adjusting for known preoperative predictors in the existing nomogram, SETD2 mutations remained associated with a higher rate of metastases after nephrectomy (HR: 2.09, 95% CI: 1.19-3.67, P = 0.011).

CONCLUSION

In the current exploratory analysis, SETD2 mutations were significant predictors of MFP among patients treated for localized ccRCC. Our findings support future studies evaluating genetic alterations in preoperative renal biopsy samples as potential predictors of treatment outcome.

Decision-making in active surveillance in kidney cancer: current trends and future urine and tissue markers

Surveillance for small renal masses is a growing choice of management amongst physicians and patients. These decisions, however, can be difficult as patient factors and tumor factors may blur the line between continued surveillance and intervention. Currently, there are no biomarkers that are readily available to aid in the decision making for patients with known renal cell carcinoma; however, many show promise. We herein review the literature of the adjunct tools that are currently available for decision making in small renal masses, but also new potential biomarkers that can potentially be of use.

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.

Robotic-assisted Partial Nephrectomy for "Very Small" (<2 cm) Renal Mass: Results of a Multicenter Contemporary Cohort

BACKGROUND

Patient with "very small" (<2 cm) renal mass can be offered active surveillance, thermal ablation, or partial nephrectomy. The management strategy will consider patient preferences and prioritize potential harms associated with each of these options. To date, outcomes of robot-assisted partial nephrectomy (RAPN) in patients with "very small" renal masses have not been reported.

OBJECTIVE

To assess the outcomes of RAPN among patients with "very small" renal masses.

DESIGN, SETTING, AND PARTICIPANTS

This was a retrospective analysis of a multi-institutional database including RAPN cases performed at eight high-volume US and European centers between 2009 and 2019. Patients were stratified into two groups according to clinical tumor size: <2 cm ("very small" renal mass, study group) and 2-4 cm (control group).

INTERVENTION

RAPN for renal masses.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Baseline characteristics and intraoperative, pathological, and postoperative data were compared between the study and the control group. A "trifecta" was used as surrogate of "surgical quality."

RESULTS AND LIMITATIONS

Overall, a total of 1019 patients were included in the analysis. Of these, 352 had a renal mass of <2 cm (34.5%) and 667 (65.5%) had a renal mass of 2-4 cm. At baseline, the study group presented a lower rate of chronic kidney disease ≥stage III (p < 0.001), a lower RENAL score (p = 0.001), and lower rates of hilar (p = 0.04) and endophytic (p = 0.02) masses. Warm ischemia time was shorter for the study group (median 14 vs 18 min, p < 0.001), which also showed a lower rate of overall postoperative complications (9.6% vs 14.7%, p < 0.001) and no major complications. In terms of oncological outcomes, three and ten patients developed a local recurrence in the study and the control group, respectively (p = 0.1). In the study group, higher estimated glomerular filtration rates were found at discharge (p = 0.001) and at the last follow-up (p = 0.007), which showed a "trifecta" achievement of 90.6%. The retrospective design may limit the generalizability of the findings.

CONCLUSIONS

Whenever an active treatment is indicated or warranted, RAPN represents a minimally invasive management option for "very small" renal masses, as it carries minimal risk of complications and has minimal impact on renal function. While both active surveillance and kidney ablation remain valid management options in these cases, RAPN can be offered and discussed with patients as it provides excellent outcomes with low morbidity.

PATIENT SUMMARY

In this report, we observed that robot-assisted partial nephrectomy represents a true minimally invasive active treatment for "very small" renal masses (<2 cm), as it carries minimal risk of complications and has minimal impact on renal function.