Initial Observation of a Large Proportion of Patients Presenting with Clinical Stage T1 Renal Masses: Results from the MUSIC-KIDNEY Statewide Collaborative

The use of nephron-sparing intervention does not appear to be compromised after a period of active surveillance for patients with cT1 renal masses

INTRODUCTION AND OBJECTIVE

It remains unknown whether the use of nephron sparing intervention (NSI) is impacted with delayed intervention after a period of active surveillance (AS) compared with immediate intervention for patients with clinically localized renal masses ≤7cm (cT1RMs). We hypothesized that the proportion of patients undergoing NSI is similar among patients undergoing immediate and delayed intervention for cT1RMs.

METHODS

We retrospective reviewed the prospectively maintained Michigan Urological Surgery Improvement Collaborative (MUSIC) registry for patients undergoing intervention for cT1RMs from 05/2017 to 09/2023. The primary outcome was type of treatment received: radical nephrectomy (RN) or NSI (partial nephrectomy, ablation, or stereotactic body radiation therapy). The main independent variable was timing of treatment: immediate (treatment within 90 days) vs. delayed intervention (>90 days). We fit a mixed-effects multivariable logistic regression model to assess for the adjusted association of immediate vs delayed intervention with the receipt of NSI and estimate an adjusted probability of NSI.

RESULTS

We identified 2,156 patients, of whom 93% underwent immediate intervention and 7% underwent a period of AS prior to delayed intervention. Median time from initial visit to intervention was 1.4 (IQR 0.9-2.0) and 13 (IQR 7.7-21) months in the immediate vs delayed intervention groups, respectively. In the multivariable model, we did not appreciate a significant association between delayed intervention with receipt of NSI (OR 0.99, 95% CI 0.57-1.70, P >0.9). The adjusted proportion of NSI was 75% and 78% for patients in the immediate and delayed intervention cohorts, respectively.

CONCLUSION

Patients undergoing delayed intervention after AS had similar use of NSI compared with those undergoing immediate intervention. Active surveillance for patients with cT1RMs does not appear to compromise the ability to perform nephron sparing interventions.

Tumour size is associated with growth rates of >0.5 cm/year and delayed intervention in small renal masses in patients on active surveillance

OBJECTIVE

To evaluate the association between tumour size and the growth rate (GR) of small renal masses (SRMs) in patients managed by active surveillance (AS).

MATERIALS AND METHODS

We queried the prospective, multi-institutional Delayed Intervention and Surveillance for Small Renal Masses (DISSRM) registry for patients on AS with an imaging interval of ≥6 months, identifying 456 patients. We tracked tumour size over time; a GR >0.5 cm/year was defined as a GR event. We used multivariable recurrent events and time-to-event Cox regression modelling to evaluate the association between tumour size and GR events (primary outcome) and tumour size and delayed intervention (DI; secondary outcome). We tested tumour size as a continuous variable and dichotomised tumour size by predefined (2-cm) and calculated (2.9-cm) cutoffs. We calculated the cutoff using maximally selected rank statistics and time to progression, defined according to the DISSRM registry.

RESULTS

The median (interquartile range) follow-up of patients on AS was 40.1 (26.4-71.2) months, during which 128 patients (28%) had ≥1 GR event, and 80 (18%) underwent DI. Larger tumour size was an independent predictor for GR events and DI when tested as a continuous and a dichotomous variable in multivariable analyses (all P < 0.05). The association was strongest when accounting for the change in tumour size over time and when applying the 2.9-cm cutoff. The study is limited by the mixed tumour pathology inert to SRMs.

CONCLUSION

Larger tumour size was independently associated with GR events and DI for patients with SRMs on AS. A 2.9-cm cutoff may provide valuable information for patient counselling.

Partial nephrectomy after a period of active surveillance: Are perioperative and pathology outcomes worsened compared to immediate surgery?

INTRODUCTION

Active surveillance (AS) is a viable strategy for managing small renal masses (SRMs) in lieu of immediate surgery, but concerns persist regarding its impact on delayed partial nephrectomy (PN) outcomes. We aimed to compare perioperative and pathological outcomes of patients initially on AS for SRMs, later undergoing PN, against those undergoing immediate PN.

MATERIALS AND METHODS

Data were extracted from a prospective institutional database (January 2018-September 2023) for patients with cT1a renal masses. Only malignancies confirmed at final pathology were included. Baseline patient and tumor characteristics and the time from AS enrollment to PN were recorded. Surgical, renal functional, and final pathology outcomes were analyzed, including histology, tumor size, pT stage, upstaging rate, and positive surgical margins. Predictors of upstaging were identified using logistic regression models.

RESULTS

Analysis included 356 patients: 307 immediate PN and 49 deferred PN after a median of 18 months in AS. Groups had comparable baseline characteristics; no significant differences emerged in surgical and postoperative outcomes. Final pathology revealed no significant disparities in tumor size, histology, positive margins, or upstaging, though pT stage distribution differed (2.4 % versus 4.3 % for pT3a, immediate versus deferred, p = 0.04). Univariable analysis identified RENAL Score (OR 1.29, 95 % C.I. 1.09-1.53, p = 0.003) and clinical tumor size (OR 1.16, 95 % C.I. 1.10-1.22, p < 0.01) as upstaging predictors, confirmed by multivariable analysis (p < 0.01).

CONCLUSION

Our comparative analysis found no worsened perioperative or adverse pathological outcomes in patients with deferred PN, supporting the safety of this approach in managing SRMs, at least as an initial option.

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.

Simplified cardiovascular index may be the best comorbidity index for clinical use in prediction of mortality for renal cancer patients

OBJECTIVE

Understanding the relationship between comorbidities and life expectancy is important in cancer patients who carry risks of cancer and noncancer-related mortality. Comorbidity indices (CI) are tools to provide an objective measure of competing risks of death. We sought to determine which CI might be best incorporated into clinical practice for patients with suspected renal cancer.

MATERIALS AND METHODS

1572 patients diagnosed with renal masses (stage I-IV) between 1998 and 2016 were analyzed for this study. Patient data were gathered from a community-based health center. Comorbidities were evaluated individually, and with 1 of 4 CI: Charlson (CCI), updated CCI (uCCI), age-adjusted CCI (aCCI), and simplified cardiovascular index (CVI). Cox-proportional hazard analysis of all-cause mortality was performed using the four CI, adjusting for the 4 CI, adjusting for age, gender, race, tumor size, and tumor stage.

RESULTS

Univariable analyses revealed the four CI were significant predictors of mortality (P < 0.05), as were age, gender, tumor size, and stage. Comorbid conditions at diagnosis included hypertension (47.8%), diabetes mellitus (47.2%), coronary artery disease (41.1%), chronic kidney disease (31.8%), peripheral vascular disease (8.0%), congestive heart failure (5.7%), chronic obstructive pulmonary disease (5.7%), and cerebrovascular disease (2.0%). When analyzing the 4 CI in multivariable survival analyses accounting for factors available at diagnosis, and analyses incorporating pathologic and recurrence data, only CVI score and uCCI remained statistically significant (P < 0.05). Limitations of this work are the retrospective nature of data collection and data from a single institution, limiting the generalizability.

CONCLUSION

Increasing comorbidity, age, tumor size, and cM stage are predictors of ACM for suspected renal cancer patients. CVI appears to provide comparable information to various iterations of CCI (uCCI, aCCI) while being the simplest to use. Utilization of CVI may assist clinicians and patients when considering between interventional and noninterventional approaches for suspected renal cancer.

Does Urologist-level Utilization of Active Surveillance for Low-risk Prostate Cancer Correspond with Utilization of Active Surveillance for Small Renal Masses?

Active surveillance (AS) for prostate cancer (CaP) or small renal masses (SRMs) helps in limiting the overtreatment of indolent malignancies. Implementation of AS for these conditions varies substantially across individual urologists. We examined the Michigan Urological Surgery Improvement Collaborative (MUSIC) registry to assess for correlation of AS between patients with low-risk CaP and patients with SRM managed by individual urologists. We identified 27 urologists who treated at least ten patients with National Comprehensive Cancer Network low-risk CaP and ten patients with SRMs between 2017 and 2021. For surgeons in the lowest quartile of AS use for low-risk CaP (<74%), 21% of their patients with SRMs were managed with AS, in comparison to 74% of patients of surgeons in the highest quartile (>90%). There was a modest positive correlation between the surgeon-level risk-adjusted proportions of patients managed with AS for low-risk CaP and for SRMs (Pearson correlation coefficient 0.48). A surgeon's tendency to use AS to manage one low-risk malignancy corresponds to their use of AS for a second low-risk condition. By identifying and correcting structural issues associated with underutilization of AS, interventions aimed at increasing AS use may have effects that influence clinical tendencies across a variety of urologic conditions. PATIENT SUMMARY: The use of active surveillance (AS) for patients with low-risk prostate cancer or small kidney masses varies greatly among individual urologists. Urologists who use AS for low-risk prostate cancer were more likely to use AS for patients with small kidney masses, but there is room to improve the use of AS for both of these conditions.

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.

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

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

Utilization of Renal Mass Biopsy for T1 Renal Lesions across Michigan: Results from MUSIC-KIDNEY, A Statewide Quality Improvement Collaborative

BACKGROUND

Renal mass biopsy (RMB) has had limited and varied utilization to guide management of renal masses (RM).

OBJECTIVE

To evaluate utilization of RMB for newly diagnosed cT1 RMs across diverse practice types and assess associations of outcomes with RMB.

DESIGN SETTING AND PARTICIPANTS

MUSIC-KIDNEY commenced data collection in September 2017 for all newly presenting patients with a cT1 RM at 14 diverse practices. Patients were assessed at ≥120 d after initial evaluation.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Demographics and outcomes were compared for patients undergoing RMB versus no RMB. Clinical and demographic characteristics were summarized by RMB status using a χ2 test for categorical variables and Student t test for continuous variables. A mixed-effects logistic regression model was constructed to identify associations with RMB receipt.

RESULTS AND LIMITATIONS

RMB was performed in 15.5% (n = 282) of 1808 patients with a cT1 RM. Practice level rates varied from 0% to 100% (p = 0.001), with only five of 14 practices using RMB in >20% of patients. On multivariate analysis, predictors of RMB included greater comorbidity (Charlson comorbidity index ≥2 vs 0: odds ratio [OR] 1.44; p = 0.025) and solid lesion type (cystic vs solid: OR 0.17; p = 0.001; indeterminate vs solid: OR 0.58; p = 0.01). RMB patients were less likely to have benign pathology at intervention (5.0% vs 13.5%; p = 0.01). No radical nephrectomies were performed for patients with benign histology at RMB. The limitations include short follow-up and inclusion of practices with low numbers of RMBs.

CONCLUSIONS

Utilization of RMB varied widely across practices. Factors associated with RMB include comorbidities and lesion type. Patients undergoing RMB were less likely to have benign histology at intervention.

PATIENT SUMMARY

Current use of biopsy for kidney tumors is low and varies across our collaborative. Biopsy was performed in patients with greater comorbidity (more additional medical conditions) and for solid kidney tumors. Pretreatment biopsy is associated with lower nonmalignant pathology detected at treatment.

Contrast-enhanced ultrasound (CEUS) imaging for active surveillance of small renal masses

PURPOSE

To assess the safety and efficacy of contrast-enhanced ultrasound (CEUS) imaging for monitoring small (< 4 cm) renal masses (SRM) in patients undergoing active surveillance (AS).

METHODS

We retrospectively selected all consecutive patients with SRMs who underwent AS for at least 6 months at our Institution between January 2014 and December 2018. CEUS imaging was performed by two experienced genitourinary radiologists at established time points. The accuracy of CEUS for monitoring SRM size was compared with that of CT scan. For solid SRMs, four enhancement patterns (EP) were recorded. Radiological progression was defined as SRM growth rate ≥ 5 mm/year.

RESULTS

Overall, 158/1049 (15.1%) patients with SRMs underwent AS. At a median follow-up of 25 months (IQR 13-39), no patient died due to renal cell carcinoma (RCC). No patients experienced CEUS-related adverse events. There was a large variability in the pattern of growth of SRMs (overall median growth rate: 0.40 mm/year), with 9.5% of SRMs showing radiological progression. The median SRM size was comparable between CEUS and CT scan examinations at all time points. The vast majority (92.7%) of SRMs did not show a change in their EP over time; and there was no association between the SRM's EP and radiological progression or SRM size. Overall, 43 (27.2%) patients underwent delayed intervention (DI); median SRM size, and median growth rate were significantly higher in these patients as compared to those continuing AS.

CONCLUSION

In experienced hands, CEUS is a safe and effective strategy for active monitoring of SRMs in well-selected patients undergoing AS.