Not-so-simple nephrectomy: Comparative analysis of radical and simple nephrectomy in a high-volume tertiary referral center.

OBJECTIVES: Simple nephrectomies can be challenging with significant morbidity. To prove the hypothesis of "not-so-simple" nephrectomy, we compared demographics, perioperative outcomes, and complications between simple and radical nephrectomy in a tertiary referral center. METHODS: We analyzed 473 consecutive radical nephrectomies (January 2018-October 2020) and simple nephrectomies (January 2016-October 2020). Univariate and multivariate analysis of perioperative outcomes utilized the Mann-Whitney U test, Chi-squared test, Mantel-Haenszel test of trend, and multiple linear regression. Radical nephrectomies were classified in cT1, cT2a, and cT2b-T3 subgroups and compared to simple nephrectomies. Minimally invasive and open techniques were compared between the two groups. Infected versus non-infected simple nephrectomies were compared. RESULTS: A total of 344 radical and 129 simple nephrectomies were included. Simple nephrectomy was an independent predictor of increased operative time (p = 0.001), length of stay (p = 0.049), and postoperative complications (p < 0.001). Simple nephrectomies had higher operative time (p < 0.001), length of stay (p = 0.014), and postoperative morbidity (p < 0.001) than cT1 radical nephrectomies and significantly more Clavien 1-2 complications than cT2a radical nephrectomies (p = 0.001). The trend was similar in minimally invasive operations. However, conversion to open rates was not significantly different. Infected simple nephrectomies had increased operative time (p < 0.001), length of stay (p = 0.005), blood loss (p = 0.016), and intensive care stay (p = 0.019). CONCLUSIONS: Patients undergoing simple nephrectomy experienced increased operative time and morbidity. Simple nephrectomy carries higher morbidity than radical nephrectomy in tumors ≤10 cm. Robotic simple nephrectomies may reduce open conversion rates. Postoperative intensive care and enhanced recovery may be essential in simple nephrectomy planning with infected pathology.

A Phase II study of neoadjuvant axitinib for reducing the extent of venous tumour thrombus in clear cell renal cell cancer with venous invasion (NAXIVA).

BACKGROUND: Surgery for renal cell carcinoma (RCC) with venous tumour thrombus (VTT) extension into the renal vein (RV) and/or inferior vena cava (IVC) has high peri-surgical morbidity/mortality. NAXIVA assessed the response of VTT to axitinib, a potent tyrosine kinase inhibitor. METHODS: NAXIVA was a single-arm, multi-centre, Phase 2 study. In total, 20 patients with resectable clear cell RCC and VTT received upto 8 weeks of pre-surgical axitinib. The primary endpoint was percentage of evaluable patients with VTT improvement by Mayo level on MRI. Secondary endpoints were percentage change in surgical approach and VTT length, response rate (RECISTv1.1) and surgical morbidity. RESULTS: In all, 35% (7/20) patients with VTT had a reduction in Mayo level with axitinib: 37.5% (6/16) with IVC VTT and 25% (1/4) with RV-only VTT. No patients had an increase in Mayo level. In total, 75% (15/20) of patients had a reduction in VTT length. Overall, 41.2% (7/17) of patients who underwent surgery had less invasive surgery than originally planned. Non-responders exhibited lower baseline microvessel density (CD31), higher Ki67 and exhausted or regulatory T-cell phenotype. CONCLUSIONS: NAXIVA provides the first Level II evidence that axitinib downstages VTT in a significant proportion of patients leading to reduction in the extent of surgery. CLINICAL TRIAL REGISTRATION: NCT03494816.

Growth and renal function dynamics of renal oncocytomas in patients on active surveillance.

OBJECTIVES: To study the natural history of renal oncocytomas and address indications for intervention by determining how growth is associated with renal function over time, the reasons for surgery and ablation, and disease-specific survival. PATIENTS AND METHODS: The study was conducted in a retrospective cohort of consecutive patients with renal oncocytoma on active surveillance reviewed at the Specialist Centre for Kidney Cancer at the Royal Free London NHS Foundation Trust (2012 to 2019). Comparison between groups was performed using Mann-Whitney U-tests and chi-squared tests. A mixed-effects model with a random intercept for patient was used to study the longitudinal association between tumour size and estimated glomerular filtration rate (eGFR). RESULTS: Longitudinal data from 98 patients with 101 lesions were analysed. Most patients were men (68.3%) and the median (interquartile range [IQR]) age was 69 (13) years. The median (IQR) follow-up was 29 (26) months. Most lesions were small renal masses, and 24% measured over 4 cm. Over half (64.4%) grew at a median (IQR) rate of 2 (4) mm per year. No association was observed between tumour size and eGFR over time (P = 0.871). Nine lesions (8.9%) were subsequently treated. Two deaths were reported, neither were related to the diagnosis of renal oncocytoma. CONCLUSION: Natural history data from the largest active surveillance cohort of renal oncocytomas to date show that renal function does not seem to be negatively impacted by growing oncocytomas, and confirms clinical outcomes are excellent after a median follow-up of over 2 years. Active surveillance should be considered the 'gold standard' management of renal oncocytomas up to 7cm.

Impact of the first surge of the COVID-19 pandemic on a tertiary referral centre for kidney cancer.

OBJECTIVE: To analyse the impact of the COVID-19 pandemic on a centralized specialist kidney cancer care pathway. MATERIALS AND METHODS: We conducted a retrospective analysis of patient and pathway characteristics including prioritization strategies at the Specialist Centre for Kidney Cancer located at the Royal Free London NHS Foundation Trust (RFH) before and during the surge of COVID-19. RESULTS: On 18 March 2020 all elective surgery was halted at RFH to redeploy resources and staff for the COVID-19 surge. Prioritizing of patients according to European Association of Urology guidance was introduced. Clinics and the specialist multidisciplinary team (SMDT) meetings were maintained with physical distancing, kidney surgery was moved to a COVID-protected site, and infection prevention measurements were enforced. During the 7 weeks of lockdown (23 March to 10 May 2020), 234 cases were discussed at the SMDT meetings, 53% compared to the 446 cases discussed in the 7 weeks pre-lockdown. The reduction in referrals was more pronounced for small and asymptomatic renal masses. Of 62 low-priority cancer patients, 27 (43.5%) were deferred. Only one (4%) COVID-19 infection occurred postoperatively, and the patient made a full recovery. No increase in clinical or pathological upstaging could be detected in patients who underwent deferred surgery compared to pre-COVID practice. CONCLUSION: The first surge of the COVID-19 pandemic severely impacted diagnosis, referral and treatment of kidney cancer at a tertiary referral centre. With a policy of prioritization and COVID-protected pathways, capacity for time-sensitive oncological interventions was maintained and no immediate clinical harm was observed.

Pattern, timing and predictors of recurrence after surgical resection of chromophobe renal cell carcinoma.

PURPOSE: Currently there are no specific guidelines for the post-operative follow-up of chromophobe renal cell carcinoma (chRCC). We aimed to evaluate the pattern, location and timing of recurrence after surgery for non-metastatic chRCC and establish predictors of recurrence and cancer-specific death. METHODS: Retrospective analysis of consecutive surgically treated non-metastatic chRCC cases from the Royal Free London NHS Foundation Trust (UK, 2015-2019) and the international collaborative database RECUR (15 institutes, 2006-2011). Kaplan-Meier curves were plotted. The association between variables of interest and outcomes were analysed using univariate and multivariate Cox proportional hazards regression models with shared frailty for data source. RESULTS: 295 patients were identified. Median follow-up was 58 months. The five and ten-year recurrence-free survival rates were 94.3% and 89.2%. Seventeen patients (5.7%) developed recurrent disease, 13 (76.5%) with distant metastases. 54% of metastatic disease diagnoses involved a single organ, most commonly the bone. Early recurrence (< 24 months) was observed in 8 cases, all staged ≥ pT2b. 30 deaths occurred, of which 11 were attributed to chRCC. Sarcomatoid differentiation was rare (n = 4) but associated with recurrence and cancer-specific death on univariate analysis. On multivariate analysis, UICC/AJCC T-stage ≥ pT2b, presence of coagulative necrosis, and positive surgical margins were predictors of recurrence and cancer-specific death. CONCLUSION: Recurrence and death after surgically resected chRCC are rare. For completely excised lesions ≤ pT2a without coagulative necrosis or sarcomatoid features, prognosis is excellent. These patients should be reassured and follow-up intensity curtailed.

Perioperative therapy in renal cancer in the era of immune checkpoint inhibitor therapy.

PURPOSE OF REVIEW: Immune checkpoint inhibitor (ICI) combination therapy has revolutionized therapy of metastatic renal cancer. The success of immunotherapy has renewed an interest to study these agents in adjuvant and neoadjuvant settings and prior to cytoreductive nephrectomy. This narrative review will give an overview of ongoing trials and early translational research outcomes. RECENT FINDINGS: In nonmetastatic renal cell carcinoma (RCC), five phase 3 adjuvant and neoadjuvant trials with ICI monotherapy or combinations are ongoing with atezolizumab (IMmotion 010; NCT03024996), pembrolizumab (KEYNOTE-564; NCT03142334), nivolumab (PROSPER; NCT03055013), nivolumab with or without ipilimumab (CheckMate 914; NCT03138512) and durvalumab with or without tremelimumab (RAMPART; NCT03288532). Phase 1b/2 neoadjuvant trials demonstrate safety, efficacy and dynamic changes of immune infiltrates and provide rationales for neoadjuvant trial concepts as well as prediction of response to therapy. In primary metastatic RCC, two phase 3 trials investigate the role of deferred cytoreductive nephrectomy following pretreatment with ICI combination (NORDICSUN; NCT03977571 and PROBE; NCT04510597). SUMMARY: The outcomes of the major phase 3 trials are awaited as early as 2023. Meanwhile, translational data from phase 1b/2 studies enhance our understanding of the tumour immune microenvironment and its dynamic changes.

Safety and feasibility of early single-dose mitomycin C bladder instillation after robot-assisted radical nephroureterectomy.

OBJECTIVES: To assess the safety and feasibility of early single-dose mitomycin C (MMC) bladder instillation after robot-assisted radical nephroureterectomy (RARNU) at a tertiary kidney cancer centre. RARNU with bladder cuff excision and subsequent MMC bladder instillation to reduce recurrence risk is the 'gold standard' for high-risk upper urinary tract urothelial carcinoma (UUTUC). We adapted a RARNU technique with precise distal ureteric dissection, bladder cuff excision and watertight bladder closure. PATIENTS AND METHODS: We retrospectively reviewed all patients undergoing RARNU for UUTUC at our centre performed as a standardised transperitoneal procedure comprising of: bladder cuff excision, two-layer watertight closure and intraoperative bladder leak test; without re-docking/re-positioning of the robotic surgical system. Patient demographics, the timing of MMC instillation, adverse events (surgical and potentially MMC-related) and length of stay (LOS) were assessed according to the Clavien-Dindo classification. RESULTS: A total of 69 patients underwent a RARNU with instillation of MMC. The median (interquartile range [IQR]) age was 70 (62-78) years. The median (IQR) day of MMC instillation was 2 (1-3) days and the median (IQR) LOS was 2 (2-4) days, with urethral catheter removal on day of discharge in all cases. Only Grade I Clavien-Dindo complications occurred in seven patients (10%); five had ileus, one a wound infection and one a self-limiting delirium, all managed conservatively. No adverse events potentially related to MMC instillation were noted within 30 days postoperatively. CONCLUSION: The use of intravesical MMC instillation given in the immediate postoperative period appears feasible and safe in patients undergoing RARNU with intraoperative confirmation of a water-tight closure ensuring early catheter-free discharge, with no significant adverse events. The potential reduction in intravesical recurrence in patients receiving early MMC needs to be assessed with longitudinal follow-up studies.

Guideline adherence for the surgical treatment of T1 renal tumours correlates with hospital volume: an analysis from the British Association of Urological Surgeons Nephrectomy Audit.

OBJECTIVE: To assess European Association of Urology guideline adherence on the surgical management of patients with T1 renal tumours and the effects of centralisation of care. PATIENTS AND METHODS: Retrospective data from all kidney tumours that underwent radical nephrectomy (RN) or partial nephrectomy (PN) in the period 2012-2016 from the British Association of Urological Surgeons Nephrectomy Audit were retrieved and analysed. We assessed total surgical hospital volume (HV; RN and PN performed) per centre, PN rates, complication rates, and completeness of data. Descriptive analyses were performed, and confidence intervals were used to illustrate the association between hospital volume and proportion of PN. Chi- squared and Cochran-Armitage trend tests were used to evaluate differences and trends. RESULTS: In total, 13 045 surgically treated T1 tumours were included in the analyses. Over time, there was an increase in PN use (39.7% in 2012 to 44.9% in 2016). Registration of the Preoperative Aspects and Dimensions Used for an Anatomical (PADUA) complexity score was included in March 2016 and documented in 39% of cases. Missing information on postoperative complications appeared constant over the years (8.5-9%).  A clear association was found between annual HV and the proportion of T1 tumours treated with PN rather than RN (from 18.1% in centres performing <25 cases/year [lowest volume] to 61.8% in centres performing ≥100 cases/year [high volume]), which persisted after adjustment for PADUA complexity. Overall and major (Clavien-Dindo grade ≥III) complication rate decreased with increasing HV (from 12.2% and 2.9% in low-volume centres to 10.7% and 2.2% in high-volume centres, respectively), for all patients including those treated with PN. CONCLUSION: Closer guideline adherence was exhibited by higher surgical volume centres. Treatment of T1 tumours using PN increased with increasing HV, and was accompanied by an inverse association of HV with complication rate. These results support the centralisation of kidney cancer specialist cancer surgical services to improve patient outcomes.

Contemporary surgical management of renal oncocytoma: a nation's outcome.

OBJECTIVE: To report on the contemporary UK experience of surgical management of renal oncocytomas. PATIENTS AND METHODS: Descriptive analysis of practice and postoperative outcomes of patients with a final histological diagnosis of oncocytoma included in The British Association of Urological Surgeons (BAUS) nephrectomy registry from 01/01/2013 to 31/12/2016. Short-term outcomes were assessed over a follow-up of 60 days. RESULTS: Over 4 years, 32 130 renal surgical cases were recorded in the UK, of which 1202 were oncocytomas (3.7%). Most patients were male (756; 62.9%), the median (interquartile range [IQR]) age was 66.8 (13) years. The median (IQR; range) lesion size was 4.1 (3; 1-25) cm, 43.5% were ≤4 cm and 30.3% were 4-7 cm lesions. In all, 35 patients (2.9%) had preoperative renal tumour biopsy. Most patients had minimally invasive surgery, either radical nephrectomy (683 patients; 56.8%), partial nephrectomy (483; 40.2%) or other procedures (36; 3%). One in five patients (243 patients; 20.2%) had in-hospital complications: 48 were Clavien-Dindo classification grade ≥III (4% of the total cohort), including three deaths. Two additional deaths occurred within 60 days of surgery. The analysis is limited by the study's observational nature, not capturing lesions on surveillance or ablated after biopsy, possible underreporting, short follow-up, and lack of central histology review. CONCLUSION: We report on the largest surgical series of renal oncocytomas. In the UK, the complication rate associated with surgical removal of a renal oncocytoma was not negligible. Centralisation of specialist services and increased utilisation of biopsy may inform management, reduce overtreatment, and change patient outcomes for this benign tumour.

Cascade Fumarate Hydratase mutation screening allows early detection of kidney tumour: a case report.

BACKGROUND: Fumarate hydratase (FH) deficiency is a rare autosomal recessive disorder which results in a major defect in cellular metabolism. It presents in infancy with progressive encephalopathy, hypotonia, seizures and failure to thrive and is often fatal in childhood. It is caused by mutations in the FH gene (1q42.1) that result in deficiency of the citric acid cycle enzyme fumarate hydratase, resulting in accumulation of fumaric acid. Heterozygous germline mutations in the FH gene predispose to an aggressive autosomal dominant inherited early-onset kidney cancer syndrome: hereditary leiomyomatosis and renal cell cancer (HLRCC). CASE PRESENTATION: Cascade FH mutation screening enabled the early diagnosis of a renal tumour in an asymptomatic parent of a child with fumarate hydratase deficiency, resulting in timely and possibly life-saving treatment. CONCLUSION: While the theoretical risk of kidney cancer in parents of children with recessive fumarate hydratase deficiency is well recognized, to our knowledge this is the first report of a kidney tumour being detected in a parent by screening performed for this indication. This underscores the importance of offering lifelong kidney surveillance to such parents and other heterozygous relatives of children born with fumarate hydratase deficiency.

Renal mass biopsy - a practical and clinicopathologically relevant approach to diagnosis.

Advancements in imaging modalities have increased the frequency of renal mass discovery. Imaging has typically been considered sufficient to guide management for a large proportion of these tumours, but renal mass biopsies (RMBs) have an increasing role in determining malignancy and can be a valuable tool for preventing unnecessary surgery in patients with benign tumours. A structured approach should be used to help to navigate the expanding repertoire of renal tumours, many of which are molecularly defined. In terms of tumour subtyping, the pathologist's strategy should focus on stratifying patients into clinically different prognostic groups according to our current knowledge of tumour behaviour, including benign, low-grade or indolent, intermediate malignant or highly aggressive. Crucial pathological features and morphological mimicry of tumours can alter the tumour's prognostic group. Thus, pathologists and urologists can use RMB to select patients with tumours at a reduced risk of progression, which can be safely managed with active surveillance within a tailored imaging schedule, versus tumours for which ablation or surgical intervention is indicated. RMB is also crucial in the oncological setting to distinguish between different high-grade tumours and guide tailored management strategies.

Nephron Sparing Treatment (NEST) for Small Renal Masses: A Feasibility Cohort-embedded Randomised Controlled Trial Comparing Percutaneous Cryoablation and Robot-assisted Partial Nephrectomy.

There is a paucity of high-level evidence on small renal mass (SRM) management, as previous classical randomised controlled trials (RCTs) failed to meet accrual targets. Our objective was to assess the feasibility of recruitment to a cohort-embedded RCT comparing cryoablation (CRA) to robotic partial nephrectomy (RPN). A total of 200 participants were recruited to the cohort, of whom 50 were enrolled in the RCT. In the CRA intervention arm, 84% consented (95% confidence interval [CI] 64-95%) and 76% (95% CI 55-91%) received CRA; 100% (95% CI 86-100%) of the control arm underwent RPN. The retention rate was 90% (95% CI 79-96%) at 6 mo. In the RPN group 2/25 (8%) were converted intra-operative to radical nephrectomy. Postoperative complications (Clavien-Dindo grade 1-2) occurred in 12% of the CRA group and 29% of the RPN group. The median length of hospital stay was shorter for CRA (1 vs 2 d; p = 0.019). At 6 mo, the mean change in renal function was -5.0 ml/min/1.73 m2 after CRA and -5.8 ml/min/1.73 m2 after RPN. This study demonstrates the feasibility of a cohort-embedded RCT comparing CRA and RPN. These data can be used to inform multicentre trials on SRM management. PATIENT SUMMARY: We assessed whether patients with a small kidney tumour would consent to a trial comparing two different treatments: cryoablation (passing small needles through the skin to freeze the kidney tumour) and surgery to remove part of the kidney. We found that most patients agreed and a full trial would therefore be feasible.

Angiotensin II increases corpus cavernosal contractility and oxidative stress in partial bladder outlet obstructed rabbits: relevance to erectile dysfunction.

INTRODUCTION: We investigated the effect angiotensin II (Ang II), a corpus cavernosal smooth muscle (CCSM) constrictor peptide, has on tissue taken from rabbits following chronic partial bladder outlet obstruction (PBOO), as this model is characterized by an increase in corpus cavernosal collagen deposition and a marked reduction and impaired relaxation of CCSM cells. AIM: To determine the interaction between Ang II and nitric oxide (NO) and the development of oxidative stress (OS) in a rabbit model of chronic PBOO. METHODS: Corpus cavernosal tissue was obtained from 12 sham-operated and 20 PBOO rabbits. Organ bath studies determined Ang II/NO interaction on CCSM function using losartan (AT1 receptor antagonist), sodium nitroprusside (SNP, NO donor), electrical field stimulation (EFS), and vardenafil (phosphodiesterase type 5 inhibitor). The role of OS in the Ang II response was also determined using diphenylene iodonium chloride (DPI), the nicotinamide adenine dinucleotide phosphate oxidase inhibitor, which inhibits superoxide production and superoxide dismutase (SOD, the enzyme that accelerates the breakdown of superoxide). MAIN OUTCOME MEASURE: Action of Ang II and AT1 receptor antagonist, as well as SOD and DPI on CCSM function. RESULTS: Ang II caused a dose-dependent contraction of CCSM strips that was enhanced in PBOO rabbits and inhibited by losartan, DPI, and SOD. CCSM relaxation induced by SNP/EFS was impaired in this model and improved by vardenafil and losartan. CONCLUSIONS: These findings imply that the increased Ang II contractile response is a pathological consequence of PBOO and that AT1 receptor inhibition may be a therapeutic approach to treat ED associated with PBOO.

Protocol for a mixed-method study to assess chronic cough in patients with renal cell carcinoma: the prevalence, impact on quality of life, trigger and potential clinical application of chronic cough as an early screening tool in patients with kidney cancer.

INTRODUCTION: Cough as a symptom of renal cell carcinoma (RCC) was first described by Creevy in 1935, and despite one (unpublished) study suggesting it may affect 31% of these patients, as well as cough being discussed in forums for patients with kidney cancer, few clinicians are aware of this association. The cough has been described as unusual in nature, resolving rapidly after treatment with nephrectomy/embolisation but returning if the tumour recurs. METHODS AND ANALYSIS: A prospective study using a questionnaire will identify the prevalence of cough in patients with suspected or confirmed RCC attending the Specialist Centre for Kidney Cancer (London, UK). A longitudinal study in a representative sample of these patients, using EQ-5D-5L and Leicester Cough Questionnaires, together with the use of semi-structured interviews with patients, will identify the impact of cough in addition to having a diagnosis of suspected or confirmed RCC on quality of life. To investigate cough mechanisms, a pilot study using cough hypersensitivity testing will be performed on patients with RCC, with and without a cough. Clinical samples (urine, blood, phlegm and breath condensate) from patients with RCC, with and without a cough, will be collected and analysed for the presence of substances known to trigger or enhance cough and compared with the results obtained from healthy volunteers. ETHICS AND DISSEMINATION: Ethical approval has been granted (UK HR REC 22/PR/0791 dated 25/08/2022). Study outputs will be presented and published nationally and internationally at relevant conferences. This study will establish the prevalence of cough in patients with suspected or confirmed kidney cancer and support the education of clinicians to consider this diagnosis in patients with chronic cough (eg, recommending protocols to include both kidneys when investigating respiratory symptoms with chest CT scans). If substances known to trigger or enhance cough are identified and elevated in clinical samples, this research could offer potential targets for treatment for this distressing symptom. TRIAL REGISTRATION NUMBER: NIHR CRN portfolio CPMS ID:53 372.

Epitheloid Angiomyolipomas of the Kidney: Rare Renal Tumors Associated With Poor Prognoses.

OBJECTIVE: To demonstrate the clinical spectrum and challenges associated with clinical management of epitheloid angiomyolipomas (eAML). METHODS: We retrospectively reviewed the surgical database of a high-volume tertiary kidney cancer center from 2015 to 2020 to identify cases with a final histological diagnosis of eAML. Descriptive analysis of all cases was conducted. RESULTS: Five surgical cases of eAMLs were identified. Two of which have had no tumor recurrence since surgery, and three patients passed away due to disease progression. CONCLUSION: eAML are rare renal tumors which the World Health Organisation (5th Edition, 2022) and International Classification of Diseases for Oncology classify as having unspecified, borderline, or uncertain behavior. Here, we report that can also demonstrate aggressive behavior with fatal consequences. Post-operative follow-up should be recommended for all, with shorter intervals for patients with poor prognostic factors.

Protocol for a MULTI-centre feasibility study to assess the use of 99mTc-sestaMIBI SPECT/CT in the diagnosis of kidney tumours (MULTI-MIBI study).

INTRODUCTION: The incidence of renal tumours is increasing and anatomic imaging cannot reliably distinguish benign tumours from renal cell carcinoma. Up to 30% of renal tumours are benign, with oncocytomas the most common type. Biopsy has not been routinely adopted in many centres due to concerns surrounding non-diagnostic rate, bleeding and tumour seeding. As a result, benign masses are often unnecessarily surgically resected. 99mTc-sestamibi SPECT/CT has shown high diagnostic accuracy for benign renal oncocytomas and other oncocytic renal neoplasms of low malignant potential in single-centre studies. The primary aim of MULTI-MIBI is to assess feasibility of a multicentre study of 99mTc-sestamibi SPECT/CT against a reference standard of histopathology from surgical resection or biopsy. Secondary aims of the study include obtaining estimates of 99mTc-sestamibi SPECT/CT sensitivity and specificity and to inform the design and conduct of a future definitive trial. METHODS AND ANALYSIS: A feasibility prospective multicentre study of participants with indeterminate, clinical T1 renal tumours to undergo 99mTc-sestamibi SPECT/CT (index test) compared with histopathology from biopsy or surgical resection (reference test). Interpretation of the index and reference tests will be blinded to the results of the other. Recruitment rate as well as estimates of sensitivity, specificity, positive and negative predictive value will be reported. Semistructured interviews with patients and clinicians will provide qualitative data to inform onward trial design and delivery. Training materials for 99mTc-sestamibi SPECT/CT interpretation will be developed, assessed and optimised. Early health economic modelling using a decision analytic approach for different diagnostic strategies will be performed to understand the potential cost-effectiveness of 99mTc-sestamibi SPECT/CT. ETHICS AND DISSEMINATION: Ethical approval has been granted (UK HRA REC 20/YH/0279) protocol V.5.0 dated 21/6/2022. Study outputs will be presented and published nationally and internationally. TRIAL REGISTRATION NUMBER: ISRCTN12572202.