The natural history of observed enhancing renal masses: meta-analysis and review of the world literature

The cost-effectiveness of immediate treatment, percutaneous biopsy and active surveillance for the diagnosis of the small solid renal mass: evidence from a Markov model

PURPOSE

The most effective diagnostic strategy for the very small, incidentally detected solid renal mass is uncertain. We assessed the cost-effectiveness of adding percutaneous biopsy or active surveillance to the diagnosis of a 2 cm or less solid renal mass.

MATERIALS AND METHODS

A Markov state transition model was developed to observe a hypothetical cohort of healthy 60-year-old men with an incidentally detected, 2 or less cm solid renal mass, comparing percutaneous biopsy, immediate treatment and active surveillance. The primary outcomes assessed were the incremental cost-effectiveness ratio measured by cost per life-year gained at a willingness to pay threshold of $50,000. Model results were assessed by sensitivity analysis.

RESULTS

Immediate treatment was the highest cost, most effective diagnostic strategy, providing the longest overall survival of 18.53 life-years. Active surveillance was the lowest cost, least effective diagnostic strategy. On cost-effectiveness analysis using a societal willingness to pay threshold of $50,000 active surveillance was the preferred choice at a $75,000 willingness to pay threshold while biopsy and treatment were acceptable ($56,644 and $70,149 per life-year, respectively). When analysis was adjusted for quality of life, biopsy dominated immediate treatment as the most cost-effective diagnostic strategy at $33,840 per quality adjusted life-year gained.

CONCLUSIONS

Percutaneous biopsy may have a greater role in optimizing the diagnosis of an incidentally detected, 2 cm or less solid renal mass.

CT-guided percutaneous cryoablation of renal masses in selected patients

PURPOSE

We analysed our experience with computed tomography (CT)-guided percutaneous cryoablation (PCA) in patients who were not surgical candidates or refused surgery for small to medium-sized renal masses.

MATERIALS AND METHODS

Two freezing cycles were applied and separated by a passive warming cycle using 1.7- and 2.4-mm cryoprobes under either general anaesthesia or sedation based on patient positioning and respiratory status. Postoperative monitoring included haematological and biochemistry evaluation and CT scan 24 h after PCA. Follow-up consisted of a multislice CT scan at 1 month and every 3 months in the first year then every 6 months thereafter.

RESULTS

Thirty-seven patients (38 lesions) underwent 40 PCA procedures; 5/37 (13.5%) had a solitary kidney. Median mass size was 35 (range 12-70) mm. No complications occurred during the procedure. Clavien grade ≥2 anaemia occurred in two patients (5.4 %): one patient required 1 U of packed red blood cells; the other required an arterial embolisation. Serum creatinine did not increase in any case. Two patients showed persisting or recurrent disease at 1 and 9 months, respectively, and both could be re-treated with PCA. All other patients showed a hypodense mass 3 months after PCA, with no contrast enhancement. Subsequent examinations showed that lesion sizes decreased and CT densitometry remained stable or increased minimally, also with no contrast enhancement.

CONCLUSIONS

PCA proved relatively easy and safe and could be considered an effective alternative for patients who are not surgical candidates or refuse surgery, as well as in patients with medium-sized lesions.

Active surveillance: a potential strategy for select patients with small renal masses

Increased abdominal imaging has led to the significant incidental detection of clinically localized renal masses. While the gold standard remains surgical excision, mortality rates from kidney cancer remain relatively unchanged implying that a proportion of small renal masses may be indolent tumors that do not require surgical intervention. As a result, active surveillance has emerged as an alternative management strategy in select patients with significant competing risks. Although the contemporary literature characterizing the natural history of untreated small renal masses is limited, recent data demonstrate that many incidental renal masses demonstrate slow growth kinetics with a low rate of progression to metastatic disease over an intermediate time period. Prospective trials are necessary to define entry and intervention criteria for active surveillance protocols.

Is there a contemporary role for percutaneous needle biopsy in the era of small renal masses?

OBJECTIVE

To evaluate based on the best available data whether there is a contemporary role for percutaneous needle biopsy in the era of small renal masses.

PATIENTS AND METHODS

SRMs are acknowledged to be tumours less than 4cm and account for 48%-66% of new kidney cancers. Renal mass biopsy (RMB), traditionally limited to specific clinical scenarios and with inherent diagnostic accuracy problems has increased in popularity in recent years and is a potential valuable tool in the assessment of SRMs. Our discussion focuses on these issues. We performed a thorough Medline literature review using a combination of the following keywords; small renal mass, renal biopsy, percutaneous renal biopsy, renal mass biopsy and renal cell carcinoma. We identified the seminal articles with data/information pertaining to renal mass biopsy in small renal masses.

RESULTS

The facts that 1) a significant number of SRMs are diagnosed in an elderly patient cohort, 2) 20% of SRMs are benign on formal histology, 3) there are various management strategies now available and 4) modern RMB has a diagnostic accuracy >90% with few complications, are all reasons why there has been renewed interest in RMB.

CONCLUSION

  There is a contemporary role for RMB in the era of SRM as the incorporation of molecular profiling of tissue from RMB would augment our ability to risk stratify SRMs on an individual patient basis and adopt management accordingly. However, clinical judgement is paramount as there remains an unpredictable non-negligible risk of disease progression and metastasis whilst on surveillance.

Small renal mass: what the urologist needs to know for treatment planning and assessment of treatment results

OBJECTIVE

Small renal mass is a new distinct clinical entity. Detection of these tumors has increased with increased use of imaging.

CONCLUSION

We know that a proportion of these tumors are not renal cell carcinoma, and imaging-guided biopsy is being increasingly used for treatment planning. The objectives of this review are to provide an update on our current understanding of the biology of small renal masses and to review approaches to the diagnosis and treatment of these lesions.

Results of laparoscopic cryoablation in the treatment of small renal masses

Context:

Study of clinical outcome in renal cryoablation.

Aims:

Laparoscopic cryoablation (LCA) is emerging as a reliable treatment option for small renal masses (SRMs) particularly in elderly patients. Our aim was to study the results of cryoablation for small renal masses in our cohort of patients.

Settings and Design:

We retrospectively studied all patients who underwent LCA for SRMs between September 2005 and July 2008.

Materials and Methods:

All patients were discussed in our multidisciplinary meeting prior to cryoablation. Our LCA protocol included two freeze-thaw cycles, achieving a core temperature of –70°C and a peripheral temperature of at least –40°C. Follow-up included serum creatinine measurements and pre- and postcontrast CT scans at 3, 6, 12, 18, and 24 months and yearly thereafter.

Statistical analysis used:

Paired samples t-test was used to study statistical difference.

Results:

Twenty-two patients underwent LCA with a mean (range) age of 68 (39–81 years) years. The mean (range) tumor size was 29 (19–45 mm) mm. Two patients required blood transfusions, one patient developed pneumonia, and another patient developed a small area of skin necrosis at the cryoneedle entry site. The average (range) hospital stay was 4 (2–14 days) days. Twenty-one patients have had CT follow-up at a mean (range) of 24 (4–42 months) months. Three of the 21 tumors showed central enhancement on follow-up CT scans, consistent with treatment failure.

Conclusions:

Laparoscopic cryoablation is a safe treatment option for SRM in a selected group of patients.

Assessment and characterisation of common renal masses with CT and MRI

Objective

Owing to the widespread use of abdominal imaging studies the detection rate of solid renal masses has increased, and an accurate characterisation of imaging features of renal masses has become more essential for case management.

Method and results

MR imaging (MRI) and computed tomography (CT) are frequently used modalities for detection and differentiation of renal masses. This article gives a review of imaging characteristics of benign and malignant renal masses, discussing their appearance in CT and MR imaging. Advanced MR techniques like diffusion-weighted imaging and apparent diffusion coefficient (ADC) mapping, which have shown promising results in the differentiation between benign and malignant renal lesions, will be introduced.

Conclusion

MRI and CT are useful in the characterisation and estimation of the prognosis for renal masses.

Small renal masses progressing to metastases under active surveillance: a systematic review and pooled analysis

BACKGROUND

The authors systematically reviewed the literature and conducted a pooled analysis of studies on small renal masses who underwent active surveillance to identify the risk progression and the characteristics associated with metastases.

METHODS

A search of the MEDLINE database was performed to identify all clinical series that reported the surveillance of localized renal masses. For studies that reported individual-level data, clinical and radiographic characteristics of tumors without progression were compared with the characteristics of tumors that progressed to metastases.

RESULTS

Eighteen series (880 patients, 936 masses) met screening criteria; and, among these, 18 patients were identified who had tumors that progressed to metastasis (mean, 40.2 months). Six studies (259 patients, 284 masses) provided individual-level data for pooled analysis. At a mean (± standard deviation) follow-up of 33.5 ± 22.6 months, the mean initial greatest tumor dimension was 2.3 ± 1.3 cm, and mean linear growth rate was 0.31 ± 0.38 cm per year. Sixty-five masses (23%) exhibited zero net growth under surveillance, and none of those masses progressed to metastasis. A pooled analysis revealed increased age (age 75.1 ± 9.1 years vs 66.6 ± 12.3 years; P = .03), an initial greatest tumor dimension (4.1 ± 2.1 cm vs 2.3 ± 1.3 cm; P < .0001), initial estimated tumor volume (66.3 ± 100.0 cm(3) vs 15.1 ± 60.3 cm(3) ; p = .0001), linear growth rate of (0.8 ± 0.65 cm per year vs 0.3 ± 0.4 cm per year; P = .0001), and a volumetric growth rate of 27.1 ± 24.9 cm(3) per year (vs 6.2 ± 27.5 cm(3) per year; P < .0001) in the progression cohort.

CONCLUSIONS

A substantial proportion of small renal masses remained radiographically static after an initial period of active surveillance. Progression to metastases occurred in a small percentage of patients and generally was a late event. The current results indicated that, in patients who have competing health risks, radiographic surveillance may be an acceptable initial approach, and delayed intervention may be reserved for patients who have tumors that exhibit significant linear or volumetric growth.

Review of the efficacy and safety of radiofrequency ablation for the treatment of small renal masses

BACKGROUND

Small renal masses are increasingly being discovered incidentally on imaging performed for another reason. The standard of care for these masses involves excision by open or laparoscopic techniques. Recently, ablative techniques such as radiofrequency ablation (RFA) and cryoablation have taken a more prominent role in the treatment algorithm for these masses. We sought to evaluate the efficacy and safety of radiofrequency ablation in the treatment of renal tumours.

METHODS

We conducted a review of the literature. There was no language restriction. We obtained studies from the following sources: the Cochrane Library, PubMed, EMBASE, LILACS and Current Controlled Trials.

RESULTS

We identified no clinical trials in the literature. Thus we described the results from case series and retrospective studies with a reasonable sample size (number of reported patients in each study > 65). Most patients undergoing RFA had T1a disease with a mean tumour size of about 3 cm. Radiofrequency ablation was usually performed percutaneously with image guidance. Reported follow-up was short and ranged from 1 to 30 months. Most series used radiographic response as a surrogate for cancer control. The rates of local recurrence of the tumour were as high as 13.0% (average 8.5%) and were slightly higher than those associated with cryoablation and partial nephrectomy. Complications included hemorrhage, ureteral strictures and loss of a renal unit.

CONCLUSION

Our review demonstrates that RFA is a suitable and promising therapy in patients with small renal tumours who are considered to be poor candidates for more involved surgery. However, clinical trials with long-term data are needed to establish the oncological efficacy.

Progression to metastatic disease from a small renal cell carcinoma prospectively followed with an active surveillance protocol

With the widespread use of abdominal imaging to evaluate other medical conditions, many renal tumours are being diagnosed at earlier stages. Older patients have experienced the most significant increase in the incidence of renal cell carcinoma (RCC). This age group frequently has significant medical comorbidities. This has led to the concept of active surveillance for select patients with renal lesions that may not affect their mortality. However, the ultimate risk of active surveillance is the potential for developing metastases. This case report presents the development of metastatic disease from a small, incidentally detected and prospectively followed RCC with asymptomatic progression.

Watchful waiting in the treatment of the small renal mass

Objectives:

To evaluate the role and feasibility of observation with regard to the small renal mass.

Methods:

We performed a literature search of MEDLINE, reviewing the world literature relevant to the natural history, role of percutaneous biopsy and surveillance of the small renal mass.

Results:

The average yearly growth rate of most small renal masses ranges from 0.1 to 0.70 cm/yr with obvious exceptions. Clinical predictors of growth such as radiographic size at presentation, age, gender and tumor characteristics are not reliable. Approximately 1% develops metastatic disease while under surveillance. Contemporary series of percutaneous biopsy of small renal masses report sensitivity for malignancy to be 90%-98%. However, false-negative results can occur. For the majority of patients, the gold standard remains surgical extirpation.

Conclusions:

Watchful waiting is an acceptable option for management of small renal masses in the surgically unfit and elderly population. More information regarding the natural history and metastatic potential of small renal masses is needed. Percutaneous needle biopsy can be successful in detecting malignancy in selected patients with small renal masses. The role of needle biopsy for the small renal mass continues to evolve

Treatment of localised renal cell carcinoma

CONTEXT

The increasing incidence of localised renal cell carcinoma (RCC) over the last 3 decades and controversy over mortality rates have prompted reassessment of current treatment.

OBJECTIVE

To critically review the recent data on the management of localised RCC to arrive at a general consensus.

EVIDENCE ACQUISITION

A Medline search was performed from January 1, 2004, to May 3, 2011, using renal cell carcinoma, nephrectomy (Medical Subject Heading [MeSH] major topic), surgical procedures, minimally invasive (MeSH major topic), nephron-sparing surgery, cryoablation, radiofrequency ablation, surveillance, and watchful waiting.

EVIDENCE SYNTHESIS

Initial active surveillance (AS) should be a first treatment option for small renal masses (SRMs) <4 cm in unfit patients or those with limited life expectancy. SRMs that show fast growth or reach 4 cm in diameter while on AS should be considered for treatment. Partial nephrectomy (PN) is the established treatment for T1a tumours (<4 cm) and an emerging standard treatment for T1b tumours (4-7 cm) provided that the operation is technically feasible and the tumour can be completely removed. Radical nephrectomy (RN) should be limited to those cases where the tumour is not amenable to nephron-sparing surgery (NSS). Laparoscopic radical nephrectomy (LRN) has benefits over open RN in terms of morbidity and should be the standard of care for T1 and T2 tumours, provided that it is performed in an advanced laparoscopic centre and NSS is not applicable. Open PN, not LRN, should be performed if minimally invasive expertise is not available. At this time, there is insufficient long-term data available to adequately compare ablative techniques with surgical options. Therefore ablative therapies should be reserved for carefully selected high surgical risk patients with SRMs <4 cm.

CONCLUSIONS

The choice of treatment for the patient with localised RCC needs to be individualised. Preservation of renal function without compromising the oncologic outcome should be the most important goal in the decision-making process.

Treatment trends for stage I renal cell carcinoma

PURPOSE

Renal cell carcinoma is increasingly diagnosed at stage I, and among stage I cases mean tumor size has been decreasing. Previous reports suggest that nephron sparing surgery is underused for small renal cell carcinomas. We determined updated, population based treatment trends for stage I renal cell carcinoma.

MATERIALS AND METHODS

The National Cancer Data Base, which captures approximately 70% of all cancer diagnoses in the United States, was queried for renal cell carcinoma in adults diagnosed between 1993 and 2007. Trends in treatment, including no surgery, total nephrectomy, partial nephrectomy and focal ablation, were analyzed among all stage I tumors and small stage I tumors categorized by size. Logistic regression was used to identify predictors of nephron sparing surgery (partial nephrectomy or focal ablation).

RESULTS

During the study period we identified 242,740 renal cell carcinomas, of which 127,691 were stage I. For all stage I tumors partial nephrectomy increased from 6.3% to 32.2% of cases and ablation increased from 1.0% to 6.8%. For tumors less than 2.0, 2.0 to 2.9 and 3.0 to 3.9 cm partial nephrectomy increased from 15.3% to 61.1%, 11.0% to 44.2% and 7.2% to 31.1%, respectively (each p<0.001). Female gender, black race, Hispanic ethnicity, lower income, older age and treatment at community hospitals were associated with lower use of nephron sparing.

CONCLUSIONS

While total nephrectomy is still likely overused for small renal cell carcinoma, nephron sparing surgery for stage I renal cell carcinoma has increased substantially in the last 15 years with about 4-fold increases across tumor sizes. These trends appear to be ongoing but sociodemographic disparities exist which must be rectified.

Recent developments in kidney cancer

Renal cell carcinoma (RCC) diagnosis and management have undergone significant shifts in the recent past. The increasing rate of diagnosis of small renal masses, often in patients at high risk of morbidity with operative treatment, has led to studies, trials and discoveries in renal mass biopsy, active surveillance and minimally invasive thermal ablation. At the other end of the disease spectrum, targeted systemic therapies for metastatic RCC have supplanted cytokine-based treatment, with significant benefits to progression and survival. Recent reviews and trials have also cemented the role of partial nephrectomy as standard surgical management for most low-stage masses, and the roles of regional lymphadenectomy and adrenalectomy concomitant with nephrectomy have been clarified. This review aims to highlight recent evidence that has emerged in the management of this complicated oncologic issue.

Optimal freeze cycle length for renal cryotherapy

PURPOSE

To our knowledge the optimal freeze cycle length in renal cryotherapy is unknown. Ten-minute time based freeze cycles were compared to temperature based freeze cycles to -20C.

MATERIALS AND METHODS

Laparoscopic renal cryotherapy was performed on 16 swine. Time based trials consisted of a double 10-minute freeze separated by a 5-minute thaw. Temperature based trials were double cycles of 1, 5 or 10-minute freeze initiated after 1 of 4 sensors indicated -20C. A 5-minute active thaw was used between freeze cycles. Control trials consisted of cryoneedle placement for 25 minutes without freeze or thaw. Viability staining and histological analysis were done.

RESULTS

There was no difference in cellular necrosis between any of the temperature based freeze cycles (p = 0.1). Time based freeze cycles showed more nuclear pyknosis, indicative of necrosis, than the 3 experimental freeze cycles for the renal cortex (p = 0.05) but not for the renal medulla (p = 0.61). Mean time to -20C for freeze cycle 1 was 19 minutes 10 seconds (range 9 to 46 minutes). In 4 of 21 trials (19%) -20C was never attained despite freezing for 25 to 63 minutes.

CONCLUSIONS

There was no difference in immediate cellular necrosis among double 1, 5 or 10-minute freeze cycles. Cellular necrosis was evident on histological analysis for trials in which -20C was attained and in freeze cycles based on time alone. With a standard 10-minute cryoablation period most treated parenchyma 1 cm from the probe never attained -20C. Cell death appeared to occur at temperatures warmer than -20C during renal cryotherapy.

Misdiagnosis of clear cell renal cell carcinoma

Clear cell renal cell carcinoma (RCC) represents the most common histological subtype of malignant kidney tumors. Based on symptoms alone, clear cell RCC is indistinguishable from other histological classes of RCC unless the tumor is present in the context of an RCC syndrome. Histopathological examination is, therefore, important to accurately identify clear cell RCC. Clear cell RCCs have characteristic morphological criteria; these tumors can be easily identified upon typical presentation, but diagnosis can be challenging when tumor cell pattern is unusual or when availability of tissue samples is limited. In this Review, the clinical, radiological and pathological characteristics of clear cell RCCs are described, as well as the potential tumors that can be confused with clear cell RCC and need to be considered in the differential diagnoses. Finally, the importance of an accurate diagnosis is highlighted in the context of the increasing use of preoperative tissue sampling and the prevalence of clear cell tumors associated with hereditary syndromes, which could have different therapeutic and prognostic implications for patients and their families.

The role of biopsy in incidental renal tumours

PURPOSE

Historically, the biopsy of renal masses was not advocated, and to date there remains some controversy on the role of biopsy for renal masses in making treatment decisions. With the widespread use of imaging methods, the incidental diagnosis of renal masses has increased, necessitating renal biopsies to better plan the management of these tumours. Here I review previous reports to define the role of biopsy in incidental renal tumours.

METHODS

Data were obtained from English-language studies listed in PubMed on the use of renal biopsy for evaluating incidental solid small renal tumours.

RESULTS

The biopsy of small renal tumours is increasingly accepted due to: the increase in the incidence of small renal tumours; the finding that a significant number of these tumours are benign; the availability of new management options, such as ablative therapy and surveillance strategies; that imaging alone is unable to predict the biological behaviour of these tumours; and advances in the pathological evaluation of the biopsies. The biopsy procedure has an acceptable complication rate but is not free of limitations. The current recommendations for the use of renal biopsy in small renal tumours are: to help in differentiating benign from malignant renal tumours; before or during ablative therapies and during the follow-up after ablative therapies, for defining treatment success or failure; and to exclude nonrenal cell primary tumours (metastasis and lymphoma) or benign conditions (abscess), which may not require surgery.

CONCLUSIONS

The biopsy of small renal tumours is a safe and accurate procedure, and can help in the planning of definitive patient management.

Active surveillance of small renal masses: progression patterns of early stage kidney cancer

BACKGROUND

Most early stage kidney cancers are renal cell carcinomas (RCCs), and most are diagnosed incidentally by imaging as small renal masses (SRMs). Indirect evidence suggests that most small RCCs grow slowly and rarely metastasize.

OBJECTIVE

To determine the progression and growth rates for newly diagnosed SRMs stratified by needle core biopsy pathology.

DESIGN, SETTING, AND PARTICIPANTS

A multicenter prospective phase 2 clinical trial of active surveillance of 209 SRMs in 178 elderly and/or infirm patients was conducted from 2004 until 2009 with treatment delayed until progression.

INTERVENTION

Patients underwent serial imaging and needle core biopsies.

MEASUREMENTS

We measured rates of change in tumor diameter (growth measured by imaging) and progression to ≥ 4 cm, doubling of tumor volume, or metastasis with histology on biopsy.

RESULTS AND LIMITATIONS

Local progression occurred in 25 patients (12%), plus 2 progressed with metastases (1.1%). Of the 178 subjects with 209 SRMs, 127 with 151 SRMs had>12 mo of follow-up with two or more images, with a mean follow-up of 28 mo. Their tumor diameters increased by an average of 0.13 cm/yr. Needle core biopsy in 101 SRMs demonstrated that the presence of RCC did not significantly change growth rate. Limitations included no central review of imaging and pathology and a short follow-up.

CONCLUSIONS

This is the first SRM active surveillance study to correlate growth with histology prospectively. In the first 2 yr, the rate of local progression to higher stage is low, and metastases are rare. SRMs appear to grow very slowly, even if biopsy proven to be RCC. Many patients with SRMs can therefore be initially managed conservatively with serial imaging, avoiding the morbidity of surgical or ablative treatment.

Active surveillance of renal cortical neoplasms: a contemporary review

INTRODUCTION

Over the past 2 decades, there has been a significant increase in the number of incidentally found small renal cortical neoplasms (RCNs). As more RCNs are being discovered in the elderly and infirmed patient populations, there has been a growing interest in the role of active surveillance (AS). Active surveillance is recommended for high surgical-risk patients and those with a reduced life expectancy. It is also an option for patients wishing to avoid surgery. We review the current literature on AS and highlight the natural history of disease, the important factors to evaluate during AS, and the contemporary role of biopsy.

METHODS AND MATERIALS

The MEDLINE database was searched using PubMed. Search terms included active surveillance, renal mass, natural history, and renal mass histology. From 1966 to present, 17 AS series were identified, all of which have been included in this summary. A summary was performed by compiling all available data and performing a weighted mean where applicable.

RESULTS

Initial tumor size does not correlate with growth rate or malignancy. The mean growth rate in large published series is low (0.28-0.34 cm/year). Tumors with high growth rates usually represent malignant lesions and typically undergo delayed intervention. Progression to metatatic disease is a low-probability event for tumors on AS (1.4%); however, this is still a risk that patients must be willing to accept. Larger tumors (cT1b and cT2) also demonstrate relatively low growth (0.57 cm/year); however, these tumors should be monitored carefully. Tumors followed for > 5 years demonstrate a low growth rate (0.15 cm/year), will not likely require intervention, and have a low chance of progression to metastatic disease.

CONCLUSION

For highly selected patients with RCN, AS is a reasonable treatment option. Age, surgical risk, comorbidities, and patient opinion must all factor into the final decision when considering a patient for AS.

Cost-effectiveness analysis of nephron sparing options for the management of small renal masses

PURPOSE

A recent increase in the detection of contrast enhancing renal masses 4 cm or smaller suspicious for malignancy has led to the widespread use of nephron sparing options. Limited data exist to help clinicians decide which of these competing nephron sparing therapies is most appropriate. We performed a cost-effectiveness analysis to evaluate the relative clinical and economic merits of commonly available nephron sparing strategies for small renal masses.

MATERIALS AND METHODS

We developed a decision analytic Markov model estimating the costs and health outcomes of treating a healthy 65-year-old patient with an asymptomatic unilateral small renal mass using competing nephron sparing options of immediate intervention (ie open and laparoscopic partial nephrectomy as well as laparoscopic and percutaneous ablation), active surveillance with possible delayed intervention and nonsurgical management with observation. Benefits were measured in quality adjusted life-years. We used a societal perspective, lifetime horizon and willingness to pay threshold of $50,000 per quality adjusted life-year gained. Model results were assessed with sensitivity analyses.

RESULTS

In the base case scenario the least costly option was observation and the optimal option was immediate laparoscopic partial nephrectomy, which had an incremental cost-effectiveness ratio of $36,645 per quality adjusted life-year gained compared to surveillance with possible delayed percutaneous ablation. Results were sensitive to age at diagnosis, health status and tumor size.

CONCLUSIONS

Immediate laparoscopic partial nephrectomy is the preferred nephron sparing option for healthy patients younger than 74 years old with a small renal mass. Surveillance with possible delayed percutaneous ablation is a cost-effective alternative for patients with advanced age or significant comorbidities. Observation maximizes quality adjusted life-years in patients who are poor surgical candidates or with limited life expectancy (less than 3 years).

Growth kinetics of renal masses: analysis of a prospective cohort of patients undergoing active surveillance

BACKGROUND

Active surveillance (AS) represents a treatment option for renal masses in patients who are not surgical candidates either because of existing comorbidities or patient choice. Among renal masses undergoing AS, some grow rapidly and require treatment or progress to metastatic disease. Patient and tumour characteristics related to this more aggressive behaviour have been poorly studied.

OBJECTIVE

To report the analysis of a multi-institutional cohort of patients undergoing AS for small renal masses.

DESIGN, SETTING, AND PARTICIPANTS

This prospective study included 82 patients with 84 renal masses who underwent AS in three Canadian institutions between July 2001 and June 2009.

INTERVENTION

All patients underwent AS for renal masses presumed to be renal cell carcinoma (RCC) as based on diagnostic imaging.

MEASUREMENTS

Age, sex, symptoms at presentation, maximum diameter at diagnosis (cm), tumour location (central/peripheral), degree of endophytic component (1-100%), and tumour consistency (solid/cystic) were used to develop a predictive model of the tumour growth rate using binary recursive partitioning analysis with a repeated measures outcome.

RESULTS AND LIMITATIONS

With a median follow-up of 36 mo (range: 6-96), the mean annual renal mass growth rate for the entire cohort was 0.25 cm/yr (standard deviation [SD]: 0.49 cm/yr). Only one patient (1.2%) developed metastatic RCC. Amongst all variables, maximum diameter at diagnosis was the only predictor of tumour growth rate, and two distinct growth rates were identified. Masses that are ≥2.45 cm in largest diameter at diagnosis grow faster than smaller masses. This series was limited by its moderate sample size, although it is the largest published prospective series to date.

CONCLUSIONS

We confirm that most renal masses grow slowly and carry a low metastatic potential. Tumour size is a predictor of tumour growth rate, with renal masses <2.45 cm growing more slowly than masses >2.45 cm.

Renal transplantation with kidneys affected by tumours

Renal transplantation confers improvement in quality of life and survival when compared to patients on dialysis. There is a universal shortage of organs, and efforts have been made to overcome this shortage by exploring new sources. One such area is the use of kidneys containing small tumours after resection of the neoplasm. This paper looks at the current evidence in the literature and reviews the feasibility of utilizing such a source.

MRI features of renal oncocytoma and chromophobe renal cell carcinoma

OBJECTIVE

The purpose of this study was to retrospectively describe the MRI features of the pathologically related entities renal oncocytoma and chromophobe renal cell carcinoma (RCC).

MATERIALS AND METHODS

Twenty-eight cases of histologically proven renal oncocytoma and 15 of chromophobe RCC evaluated with preoperative MRI from January 2003 through June 2009 at our institution were independently reviewed for an array of MRI features by two radiologists blinded to the final histopathologic diagnosis. These features were tabulated and compared between chromophobe RCC and renal oncocytoma by use of the Mann-Whitney test and binary logistic regression.

RESULTS

Renal oncocytoma and chromophobe RCC showed no significant difference in size or any of 16 qualitative imaging features (p = 0.0842-1.0, reader 1; p = 0.0611-1.0, reader 2). Microscopic fat, hemorrhage, cysts, infiltrative margins, perinephric fat invasion, renal vein invasion, enhancement homogeneity, and hypervascularity were each observed in less than 20% of cases by both readers. A central scar and segmental enhancement inversion (a recently described finding in which early contrast-enhanced images show relatively more enhanced and less enhanced intralesional components with inversion of their relative enhancement on later images) were observed by both readers in at least 10% of cases of both renal oncocytoma and of chromophobe RCC with no significant difference between the two entities (p = 0.2092-0.2960).

CONCLUSION

We have presented the largest series to date of the MRI features of both renal oncocytoma and chromophobe RCC. These related entities exhibited similar findings, and no MRI features were reliable in distinguishing between them.

Cryoablation vs. radiofrequency ablation for small renal masses

RATIONALE AND OBJECTIVES

Cancer of the kidney is the third most common cancer of the urinary tract, and renal cell carcinoma is the most lethal of all genitourinary tumors. The incidental discovery of renal cell carcinoma has increased with increased use of cross-sectional imaging. Concomitantly, minimally invasive ablative technologies, including image-guided cryoablation, radiofrequency ablation, and others, have evolved as therapeutic options for small renal masses.

MATERIALS AND METHODS

Between 2006 and 2009, 111 patients (age range, 31-91 years; mean age, 70 years) underwent percutaneous computed tomography-guided thermal ablation for suspected renal cell carcinoma at two major academic centers. Outcomes data were retrospectively collected and analyzed to compare recurrence rates for patients undergoing radiofrequency ablation (n = 41) versus cryoablation (n = 70).

RESULTS

There were four cases of suspicious enhancement on follow-up computed tomography or magnetic resonance imaging in each group, with cumulative imaging recurrence rates of 11% and 7% for radiofrequency ablation and cryoablation, respectively. Log rank test analysis revealed no significant difference between rates of imaging recurrence between the two groups (P = .6044).

CONCLUSIONS

These results suggest that the use of cryoablative technology will result in similar outcomes compared with radiofrequency ablation.

Prognostic variables and nomograms for renal cell carcinoma

The term renal cell carcinoma (RCC) is used to describe a heterogeneous group of tumors that vary histologically, genetically and molecularly. Extensive research has been conducted to identify characteristics that predict outcomes among patients with RCC. In addition to histological subtype these include tumor size, patient age, mode of presentation and various hematological indices, among others. Several groups have incorporated these clinical and pathological features into nomograms which help the clinician better define individual patient prognosis and direct the optimum therapeutic approach. In the present article we review these prognostic variables and nomograms for RCC.

Thermal ablation of renal cell carcinoma: triage, treatment, and follow-up

The incidence of renal cell carcinoma (RCC) is increasing. With the increasing emphasis on minimally invasive nephron-sparing surgery, thermal ablation is playing a larger role in the management of patients with this disease. This review outlines imaging management, intraoperative and percutaneous ablation, and postprocedural follow-up of RCC.

Renal mass sampling: an enlightened perspective

Renal mass sampling (RMS) can be carried out by core biopsy or fine needle aspiration with each presenting potential advantages and limitations. The literature about RMS is confounded by a lack of standardized techniques, ambiguous terminology, imprecise definitions of accuracy, substantial rates of non-informative biopsies, and recurrent diagnostic challenges with respect to eosinophilic neoplasms. Despite these concerns, RMS has an expanding role in the evaluation and treatment of renal masses, in order to stratify biological aggressiveness and guide management that can range from surgery to active surveillance. Non-informative biopsies can be managed with surgical excision or repeat biopsy, with the latter showing encouraging results in recent studies. We propose a new classification in which all biopsies are categorized as non-informative versus informative, with the latter being subclassified as confirmed accurate, presumed accurate or confirmed inaccurate. This terminology will facilitate the comparison of results from various studies and stimulate progress. Incorporation of novel biomarkers and molecular fingerprinting into RMS protocols will likely allow for more rational management of patients with renal masses in the near future.

Extracorporeal stereotactic radiosurgery for small renal masses

Over the past decade we have witnessed both a grade and stage migration for renal cell carcinoma. This shift in clinicopathology has been met with a paradigm shift in the treatment of these renal mass lesions. This trend has evolved from laparoscopic extirpation to needle-based and now extracorporeal ablation. At the forefront of the extracorporeal, minimally invasive treatment modalities is radiosurgical ablation. Still in its inaugural phase, renal radiosurgery is devoid of any long-term studies; however, short-term studies thus far show enormous potential. Herein we present the current status of radiosurgical ablation of small renal masses.

Efficacy of laparoscopic renal cryoablation as an alternative treatment for small renal mass in patients with poor operability: experience from the Korean single center

OBJECTIVE

The aim of this work was to evaluate the efficacy and safety of laparoscopic renal cryoablation (LRC) for the treatment of incidentally found small renal masses in patients with poor operability, from our initial experience in Korea.

MATERIALS AND METHODS

From June 2005 to April 2009, surgical and oncologic outcomes were evaluated from a database of 45 renal tumors in 39 patients who underwent LRC due to a high American Society of Anesthesiology (ASA) physical status score (i.e., over 3) or old age (i.e., over 70 years old).

RESULTS

Mean (range) age was 63.3 years (range, 43-81), and mean tumor size was 2.5 cm (range 0.7-3.9). Mean of ASA physical status score of whole patients was 2.8 (range, 1-4), and 79.4% (31/39) of patients had an ASA physical status score over 3. Eleven patients (28.2%) were over 70 years old. Among 45 treated lesions, 23 (51.1%) were exophytic tumors, 17 (37.8%) were endophytic tumors, and the other 5 (11.1%) were mesophytic tumors. Mean operating time was 173.7 minutes (range, 110-220), and mean blood loss was 106.3 mL (range, 40-150). None of the patients developed major complications, including adjacent organ injury, collecting system injury, open surgical conversion, or conversion to nephrectomy. Pathologic examination revealed that 60% (27/45) of lesions were renal-cell carcinoma (RCC). During a mean follow-up duration of 23.5 months (range, 6-53), radiologic evidence of tumor recurrence was found in 1 patient (3.7% for RCC). With the exception of this patient, all other patients have remained free of recurrence or metastasis, as determined by a periodic radiologic work-up. Serum creatinine remains stable, with no statistical difference, compared to preoperative levels, in both whole patients and patients with solitary kidney.

CONCLUSIONS

In this series, LRC for small renal tumors showed favorable oncologic and surgical outcomes, including maintenance of renal function, without adverse effects in selected patients with poor operability.

[Characterization and outcome of renal cancers ≤ 4cm treated by surgery]

PURPOSE

In a retrospective study, we described the characteristics and the outcome of renal cancers less than or equal to 4cm treated by surgical excision.

MATERIAL

Two hundred and eighty four cancers less than or equal to 4cm on preoperative CT scan (T1a) were extracted from our database. We studied, the presence of symptoms, the ECOG and ASA scores, the size, the histological type and the Fuhrman grade. The follow up was clinical, biological and radiological.

RESULTS

The mean age was 60.8 years. 21% of patients were symptomatic. The renal capsule was intact in 182 cases (64.08%), the urinary tract in 267 cases (94.01%). Seven patients (2.46%) were metastatic with tumors greater than or equal to pT3a. The most common histological types were the conventional renal cell carcinoma (78.52%) and the papillary renal cell carcinoma (16.55%). 76.06%. of the tumors were low grade. With a median of 66.9 months, 33 patients died (11.61%) . For N0M0 patients, with a median of 59.3 months, three specific deaths (1.19%) and 17 deaths from other causes (6.77%) were observed. The average survival of N0M0 group was 227.2 months.

CONCLUSION

The renal cell carcinoma less than or equal to 4cm was a heterogeneous group including locally advanced and aggressive or metastatic tumors. For localized forms, surgical excision provided an effective long-term treatment regardless the histological type or the tumor grade.