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

[Current treatment of small renal masses]

Incidental diagnosis of renal carcinoma (RC) is increasingly common due to widespread use of radiodiagnostic techniques for other conditions. In developed countries, incidental tumor account for more than 40% of detected tumors, and 80% of solid kidney tumors less than 4 cm in size are malignant. Standard treatment for these tumors is partial nephrectomy, and their relapse rate is 1%-2% The higher increase in diagnosis of this disease has occurred in patients aged 70 to 90 years, a group where associated comorbidities are very common. In the past two decades, in parallel to development of radiographic techniques, two ablation procedures achieving tumor necrosis through cold, cryotherapy, and through heat, radiofrequency, have become established. These procedures achieve 95% short- and long-term remissions in tumors less than 4 cm in size. In addition, since these procedures may be performed percutaneously, both complications and hospital stay have decreased. As early as in 1995, Bosniak, based on observation of the growth and behavior of small RCs for longer than 8 years, advocated a watchful waiting or active surveillance attitude. This article reports cryotherapy, our radiofrequency series, and a literature review.

CONCLUSIONS

In the event of elderly patients, concomitant diseases advising against surgery, multiple renal tumors, a solitary kidney, or patients who reject surgery, ablation procedures may be safe and effective when performed by expert hands, achieving mid-term oncological results similar to partial nephrectomy. Active surveillance has also been shown to be safe in the mid-term in adequately informed patients. To improve indications, new diagnostic procedures that help us differentiate the potentially more aggressive tumors will be required. Larger series and longer follow-ups are neede to confirm current results.

[Renal mass biopsy: results and safety in 2009]

The role of renal mass biopsies has been limited by suboptimal results in terms of diagnostic reliability, and their scant repercussion upon therapeutic decision taking. Recently, however, renal mass biopsies have generated renewed interest among urologists, as a result of the increased incidence of renal tumors, the introduction of new management options, and advances in histological diagnosis. A review has been made, based on a PubMed search of the most relevant publications on renal tumor biopsies in recent years. The most recent clinical studies reveal a high degree of diagnostic reliability in differentiating malignancy, histological type and grade in percutaneous biopsies of renal tumors, with a low rate of associated complications. However, routine use of the technique remains controversial, and its indications limited, due to the scant capacity of the renal biopsy findings to modify treatment decision.

Natural history, growth kinetics, and outcomes of untreated clinically localized renal tumors under active surveillance

BACKGROUND

The growth kinetics of untreated solid organ malignancies are not defined. Radiographic active surveillance (AS) of renal tumors in patients unfit or unwilling to undergo intervention provides an opportunity to quantify the natural history of untreated localized tumors. The authors report the radiographic growth kinetics of renal neoplasms during a period of surveillance.

METHODS

The authors identified patients with enhancing renal masses who were radiographically observed for at least 12 months. Clinical and pathological records were reviewed to determine tumor growth kinetics and clinical outcomes. Tumor growth kinetics were expressed in terms of absolute and relative linear and volumetric growth.

RESULTS

The authors identified 172 renal tumors in 154 patients under AS. Median tumor diameter and volume on presentation were 2.0 cm (mean, 2.5; range, 0.4-12.0) and 4.18 cm(3) (mean, 20.0; range, 0.033-904). Median duration of follow-up was 24 months (mean, 31; range, 12-156). A significant association between presenting tumor size and proportional growth was noted, with smaller tumors growing faster than larger tumors. Thirty-nine percent (68 of 173) of tumors underwent delayed intervention, and 84% (57 of 68) were pathologically malignant. Progression to metastatic disease was noted in 1.3% (2 of 154) of patients.

CONCLUSIONS

The authors demonstrated the association between a tumor's volume and subsequent growth, with smaller tumors exhibiting significantly faster volumetric growth than larger tumors, consistent with Gompertzian kinetics. Surveillance of localized renal tumors is associated with a low rate of disease progression in the intermediate term, and suggests potential overtreatment biases in select patients.

Segmental enhancement inversion at biphasic multidetector CT: characteristic finding of small renal oncocytoma

PURPOSE

To retrospectively determine the usefulness of segmental enhancement inversion during the corticomedullary phase (CMP) and early excretory phase (EEP) of biphasic multidetector computed tomography (CT) in differentiating small renal oncocytoma from renal cell carcinoma (RCC).

MATERIALS AND METHODS

This retrospective study was institutional review board approved; informed consent was waived. Between January 2004 and December 2006, 98 patients with pathologically confirmed renal masses smaller than 4 cm (10 renal oncocytomas and 88 RCCs) were included in this study. Segmental enhancement inversion was defined as follows: In a mass with two segments showing different degrees of enhancement during CMP, the relatively highly enhanced segment became less enhanced during EEP, whereas the less-enhanced segment during CMP became highly enhanced during EEP. Two experienced radiologists retrospectively assessed the presence of segmental inversion in all masses and measured attenuation with consensus. The Fisher exact test was used to determine the significance of segmental enhancement inversion in differentiating small renal oncocytoma from RCC.

RESULTS

Eight of 10 renal oncocytomas and only one of 88 RCCs showed segmental inversion during CMP and EEP, which significantly differentiated small renal oncocytomas and RCCs (P < .0001). For differentiating oncocytoma from RCC, segmental inversion was found to have a sensitivity of 80% (eight of 10), a specificity of 99% (87 of 88), a positive predictive value of 89% (eight of nine), and a negative predictive value of 98% (87 of 89). The mean values of the attenuation differences shown by two segments during CMP and EEP were 62.75 HU +/- 36.96 (standard deviation) and -36.88 HU +/- 20.02, respectively.

CONCLUSION

Segmental enhancement inversion during CMP and EEP was found to be a characteristic enhancement pattern of small renal oncocytoma at biphasic multidetector CT and it may help in differentiating small oncocytoma from RCC.

SUPPLEMENTAL MATERIAL

http://radiology.rsnajnls.org/cgi/content/full/2522081180/DC1.

Surveillance as an option for the treatment of small renal masses

OBJECTIVES. To review the natural history and biological potential of small renal masses in order to evaluate surveillance as a treatment option. METHODS. Literature search of Medline and additional references from non-Medline-indexed publications concerning surveillance of small renal masses. RESULTS. The natural history and biological potential of small renal masses can still not be unambiguously predicted at present. There seems to be no clear correlation between tumour size and presence of benign histology. The majority of small renal masses grow and the majority are cancer, but one cannot safely assume that a lack of growth on serial CT scans is the confirmation of absence of malignancy. Needle core biopsies could be used to help in decision making. They show a high accuracy for histopathological tumour type but are less accurate in evaluating Fuhrman grade. CONCLUSIONS. At present, surveillance of small renal masses should only be considered in elderly and/or infirm patients with competing health risks, in those with a limited life expectancy, and in those for whom minimal invasive treatment or surgery is not an option. In all other patients, active surveillance should only be considered in the context of a study protocol. Long-term, prospective studies are needed to provide a more accurate assessment of the natural history and metastastic potential of small renal masses.

The contemporary role of surgery in kidney cancer

The diagnosis and treatment of renal cell carcinoma (RCC) has been the subject of major changes since the late 1980s. Initially, surgery was the only treatment available, but more recently, systemic therapies have been developed, and their introduction has modified some of the surgical indications for rcc. In addition, refinements in surgical technique and the introduction of minimally invasive approaches have revolutionized patient care and bear the promise of even more improvements to come. This paper provides an up-to-date overview of recent developments in the surgical treatment of RCC.

Hybrid renal cell carcinomas containing histopathologic features of chromophobe renal cell carcinomas and oncocytomas have excellent oncologic outcomes

BACKGROUND

Modern histopathology is able to differentiate chromophobe renal cell carcinomas (cRCCs), oncocytomas, and chromophobe-oncocytic hybrid RCCs; however, the true frequency and clinical courses of these tumors remain unclear.

OBJECTIVE

To determine the clinical course of hybrid RCC.

DESIGN, SETTING, AND PARTICIPANTS

Ninety-one surgically treated tumors, originally classified as oncocytoma or cRCC, were slide reviewed and reclassified by an experienced uropathologist. Immunohistochemical cytokeratin-7 (CK7) staining was used to distinguish oncocytoma (CK7 positive in <10% of the cells) and hybrid RCCs (CK7 positive in >10% of the cells).

INTERVENTIONS

Radical tumor nephrectomy or nephron-sparing surgery.

MEASUREMENTS

Recurrence-free and tumor-specific survival.

RESULTS AND LIMITATIONS

Overall, 16 tumors (17.6%) were hybrid RCCs, 32 tumors were cRCCs, and 43 tumors were pure oncocytomas. Perinephric tissue invasion (pT3a) was found in one pure oncocytoma and in two hybrid RCCs. The pathologic stage for cRCC was pT1 in 50% of tumors (n=17), pT2 in 23.5% of tumors (n=8), and pT3a in 26.5% of tumors (n=9). Low-grade RCC was found in 76.5% of tumors (n=26), and vascular invasion was found in 11.8% of tumors (n=4). After a mean follow-up of 50 mo, no oncocytomas or hybrid RCCs were found, but two cRCCs had recurred. The 3-yr tumor-specific survival rates for patients with oncocytoma, hybrid RCCs, and cRCC were 100%, 100%, and 97%, respectively.

CONCLUSIONS

Hybrid RCCs are more common than expected. The survival rate is 100% for both hybrid RCCs and oncocytomas. Hybrid RCCs may be candidates for active surveillance, and surgery may be unnecessary. CRCCs should be treated because a small proportion of these tumors exhibit aggressive clinical courses.

Metastatic renal cell carcinoma risk according to tumor size

PURPOSE

Recent evidence suggests significantly discordant findings regarding tumor size and the metastasis risk in renal cell carcinoma cases. We present our experience with renal cell carcinoma. We evaluated the association between tumor size and the metastasis risk in a large patient cohort.

MATERIALS AND METHODS

Using our prospectively maintained nephrectomy database we identified 2,691 patients who were treated surgically for a sporadic renal cortical tumor between 1989 and 2008. Associations between tumor size and synchronous metastasis at presentation (M1 renal cell carcinoma) were evaluated with logistic regression models. Metastasis-free survival after surgery was estimated using the Kaplan-Meier method in 2,367 patients who did not present with M1 renal cell carcinoma and were followed postoperatively.

RESULTS

Of the 2,691 patients 162 presented with metastatic renal cell carcinoma. Only 1 of 781 patients with a tumor less than 3 cm had M1 renal cell carcinoma at presentation and tumor size was significantly associated with metastasis at presentation (for each 1 cm increase OR 1.25, p <0.001). Of the 2,367 patients who did not present with metastasis metastatic disease developed in 171 during a median 2.8-year followup. In this group only 1 of the 720 patients with renal cell carcinoma less than 3 cm showed de novo metastasis during followup. Metastasis-free survival was significantly associated with tumor size (for each 1 cm increase HR 1.24, p <0.001).

CONCLUSIONS

In our experience tumor size is significantly associated with synchronous and asynchronous metastases after nephrectomy. Our results suggest that the risk of metastatic disease is negligible in patients with tumors less than 3 cm.

Focal therapy for kidney cancer: a systematic review

PURPOSE OF REVIEW

Surgical excision remains the standard of care for treatment of localized small renal masses (SRMs). Laparoscopic and percutaneous minimally invasive ablative technologies are being increasingly employed in current urologic practice. We review recent literature regarding focal ablative treatments of SRMs.

RECENT FINDINGS

Most cryoablations are performed using a laparoscopic approach, whereas radiofrequency ablation (RFA) of the SRM is more commonly administered percutaneously. Pretreatment biopsy is performed more often for lesions treated by cryoablation than RFA with a significantly higher rate of indeterminate or unknown pathology for SRMs undergoing RFA versus cryoablation (P < 0.0001). Currently available data suggest that cryoablation results in lower retreatments (P < 0.0001), less local tumor progressions (P < 0.0001) and may be associated with a decreased risk of metastatic progression compared with RFA. It is unclear whether these differences are a function of the technologies or their application. Given the excellent results reported for active surveillance of the SRM in selected patients, the extent to which focal ablation alters the natural history of SRMs has not yet been established.

SUMMARY

Currently, data on the ability of interventions for SRMs to affect the natural history of these masses are lacking. Prospective randomized evaluations of available clinical approaches to SRMs are needed.

High-intensity focused ultrasound for the treatment of renal masses: current status and future potential

PURPOSE OF REVIEW

To outline the current status of high-intensity focused ultrasound (HIFU) for the treatment of renal tumors.

RECENT FINDINGS

Application of extracorporeal HIFU for renal tumors is well tolerated with no serious perioperative complications. However, the techniques available do not permit sufficient tumor destruction that can be considered as an alternative to surgical extirpation. Laparoscopic HIFU avoids problems with respiratory movement and interphases and may achieve a greater rate of tumor destruction.

SUMMARY

At the current time, HIFU of renal tumors has to be considered an experimental treatment approach. Prospective evaluation of laparoscopic HIFU is necessary to evaluate its oncologic efficacy.

Is age a prognostic factor for treatment outcome in renal cell cancer-A comprehensive review

Life expectancy gradually increases in the Western part of the world. Older patients may present with small, localized tumours and/or advanced or metastatic disease and still, potentially, have a considerable life expectancy. The consequence of the increased life span is that in older patients all potential treatments have to be discussed. A critical review of the literature regarding the treatment of different stages of renal cell cancer (RCC) in the elderly patient group was conducted. Elderly people with small renal masses are up to 3.5 times more likely to have a benign lesion. The oncological outcome from nephron sparing surgery (NSS), whether by means of laparoscopy or by means of open surgery, seems not to be different between young and old patients. No relationship between local recurrence and metastatic progression rates and patient age has been demonstrated. The outcome from systemic treatments in advanced/metastatic disease has been studied, no differences were observed between age groups, although toxicity profiles might differ between the younger and older patient groups.

Renal cell carcinoma

Considerable progress has been made in the treatment of patients with renal cell carcinoma, with innovative surgical and systemic strategies revolutionising the management of this disease. In localised disease, partial nephrectomy for small tumours and radical nephrectomy for large tumours continue to be the gold-standard treatments, with emphasis on approaches that have reduced invasiveness and preserve renal function. Additionally, cytoreductive nephrectomy is often indicated before the start of systemic treatment in patients with metastatic disease as part of integrated management strategy. The effectiveness of immunotherapy, although previously widely used for treatment of metastatic renal cell carcinoma, is still controversial, and is mainly reserved for patients with good prognostic factors. Development of treatments that have specific targets in relevant biological pathways has been the main advance in treatment. Targeted drugs, including inhibitors of the vascular endothelial growth factor and mammalian target of rapamycin pathways, have shown robust effectiveness and offer new therapeutic options for the patients with metastatic disease.

Small renal masses: incidental diagnosis, clinical symptoms, and prognostic factors

Introduction. The small renal masses (SRMs) have increased over the past two decades due to more liberal use of imaging techniques. SRMs have allowed discussions regarding their prognostic, diagnosis, and therapeutic approach. Materials and methods. Clinical presentation, incidental diagnosis, and prognosis factors of SRMs are discussed in this review. Results. SRMs are defined as lesions less than 4 cm in diameter. SRM could be benign, and most malignant SMRs are low stage and low grade. Clinical symptoms like hematuria are very rare, being diagnosed by chance (incidental) in most cases. Size, stage, and grade are still the most consistent prognosis factors in (RCC). An enhanced contrast SRM that grows during active surveillance is clearly malignant, and its aggressive potential increases in those greater than 3 cm. Clear cell carcinoma is the most frequent cellular type of malign SRM. Conclusions. Only some SRMs are benign. The great majority of malign SRMs have good prognosis (low stage and grade, no metastasis) with open or laparoscopic surgical treatment (nephron sparing techniques). Active surveillance is an accepted attitude in selected cases.

A population-based comparison of survival after nephrectomy vs nonsurgical management for small renal masses

OBJECTIVE

To examine population-based rates of cancer-specific and other-cause mortality after either non-surgical management (NSM) or nephrectomy, in patients with small renal masses, as several reports from selected institutions support the applicability of surveillance in patients with small renal masses, but there are no population-based studies confirming the general applicability of this therapy.

PATIENTS AND METHODS

Of 43 143 patients with renal cell carcinoma identified in the 1988-2004 Surveillance, Epidemiology and End Results database, 10 291 had localized small renal masses (<or=4 cm) and were offered NSM (433, 4.2%) or nephrectomy (9858, 95.8%). Univariable matched and multivariable unmatched competing-risks regression models were used in the analyses.

RESULTS

Cumulative incidence plots based on unmatched data, where the effect of other-cause mortality was controlled for, showed a 5.2%, 6.5% and 9.4% survival benefit for nephrectomy vs NSM at 1, 2 and 5 years after nephrectomy or diagnosis, respectively. The same magnitude of the benefit (4.5%, 5.6% and 8.0%) persisted in analyses matched for age, tumour size and year of diagnosis or of nephrectomy. Finally, in multivariable analyses, treatment type, age, tumour size and year of diagnosis or of nephrectomy were independent predictors.

CONCLUSION

Relative to nephrectomy, NSM appears to undermine the overall and cancer-specific survival of patients with small renal masses by as much as 9.4%, at 5 years.

Effect of renal cancer size on the prevalence of metastasis at diagnosis and mortality

PURPOSE

We determined the relationship between the prevalence of metastasis at presentation and cancer specific mortality with tumor size in renal cancer cases using a large cancer database.

MATERIALS AND METHODS

The Surveillance, Epidemiology and End Results data set was analyzed for renal tumors diagnosed from 1998 to 2003. A total of 24,253 patients were included. The prevalence of metastasis and cancer specific survival as a function of tumor size were evaluated using linear and nonlinear curve fitting methods. Metastatic cases with tumors 2.5 cm or less were individually reconfirmed case by case for accuracy.

RESULTS

Increasing tumor size correlated with a higher prevalence of metastasis at diagnosis (range 1.4% for tumors 1 cm or less to 50.9% for tumors greater than 15 cm). Five-year cancer specific mortality in treated patients was also closely related to tumor size (range 3.5% for tumors 1 cm or less to 50.9% for tumors greater than 15 cm). In each instance the relationship was sigmoidal rather than linear and it was best modeled using a quadratic function. The most rapid increase in the prevalence of metastasis and mortality was noted for tumors 4 to 12 cm. In treated patients with tumors 1 cm or less, 1.1 to 2, 2.1 to 3 and 3.1 to 4 the prevalence of metastasis at diagnosis was 1.4%, 2.5%, 4.7% and 7.4%, and the 5-year cancer specific mortality rate was 3.5%, 3.8%, 4.1% and 5.3%, respectively.

CONCLUSIONS

In cases of renal cancer the prevalence of metastasis at presentation and 5-year cancer specific mortality increase in a nonlinear sigmoidal relationship with tumor size.

The haphazard approach to the early detection of asymptomatic renal cancer: results from a contemporary executive health programme

OBJECTIVE To compare the detection of asymptomatic renal cell carcinoma (RCC) in an executive health programme (EHP) that uses traditional methods of screening (history, physical examination and urine analysis) to programmes that screen by renal imaging. PATIENTS AND METHODS We retrospectively reviewed case records from patients undergoing executive health examinations at Mayo Clinic between 1 January 2002 and 30 September 2007. Results Of 32 310 patients, 18 RCCs were detected; of these, 13 (72%) were detected by the EHP and five (28%) were missed by the initial EHP screening process but subsequently discovered within 4-24 months. Of the 13 detected through the EHP, eight were discovered incidentally, two because of symptoms, and three because of asymptomatic microscopic haematuria (AMH). Of the 13, 12 were classified as early-stage cancers (Stage I). By contrast, of the five cancers missed by the EHP screening process, two were diagnosed because of the development of symptoms and only one was classified as Stage I. To date, two of these patients whose cancers were undetected by the EHP developed metastasis and one of them has died. Both had been followed in the EHP for years and neither had MH in multiple specimens. CONCLUSION Our EHP follows standard policy and relies on a history, physical examination and urine analysis to decide who to evaluate for asymptomatic RCC. This practice missed >70% of the potentially diagnosable cancers. The patients with RCCs that were discovered initially by the EHP fared better than those whose diagnosis was delayed. Our detection rate of four per 10 000 was only a fraction of those reported by programmes using imaging as a screening tool. The logic behind our current approach to the early detection of asymptomatic RCC needs to be reassessed. AMH is coincidental in most cases and patients could forego imaging if they are unsuitable candidates for screening. However, AMH will miss most treatable cancers and is not an appropriate screening test for an early detection programme. In the absence of reliable biomarkers, renal imaging should be the primary screening tool for detecting asymptomatic RCC in informed, clinically suitable individuals enrolled in an early detection programme.

Observation should be considered as an alternative in management of renal masses in older and comorbid patients

BACKGROUND

Renal masses diagnosed in older and comorbid patients represent a challenge with regard to treatment.

OBJECTIVE

To evaluate clinical outcome and tumor progression in patients with renal masses managed by observation due to age and comorbidity.

DESIGN, SETTING, AND PARTICIPANTS

The medical records of 63 consecutive patients with renal masses primarily managed by observation during 2002-2007 were reviewed retrospectively and analyzed. The mean age for all patients at diagnosis was 76.6 yr, and 59% were male. Mean tumor size was 4.3 cm in diameter at diagnosis. Of these, 30% had Eastern Cooperative Oncology Group performance status (PS) of 2 or 3, 78% were American Society of Anesthesiologists (ASA) class 3, and the patients had a mean of 2.8 other medical conditions.

MEASUREMENTS

Registration of age, ASA class, PS, comorbid conditions, computed tomography scans, primary tumor size, tumor growth rate, pathology parameters, observation time, survival time.

RESULTS AND LIMITATIONS

Five-year overall survival (OS) and cancer-specific survival (CSS) rates were 42.8% and 93.3%, respectively. For tumors < or =4.0 cm in size, 5-yr CSS was 100%. Nine patients received delayed radical treatment, none of whom had later progression of the disease. In 18 patients histopathologic diagnosis of the renal masses were available, and in 15 patients (83%) renal cell carcinoma (RCC) was verified. The annual growth rate was <1cm/yr in 85.4% of the cases. In tumors < or =4.0 cm, only 1 of 27 tumors (3.7%) grew faster than 1cm/yr.

CONCLUSIONS

Management of renal masses by observation among older and comorbid patients seems to give acceptable results with regard to OS and CSS rates after 5 yr. The risk of disease progression is significantly higher in patients with larger sized renal masses (>4 cm). Thus, selection for observation in this group has to be stricter than in a group of patients with smaller sized renal masses (< or =4.0 cm).

Cryoablation or radiofrequency ablation of the small renal mass : a meta-analysis

BACKGROUND

The incidence of renal cell carcinoma is rising because of incidental detection of small renal masses (SRMs). Although surgical resection remains the standard of care, cryoablation and radiofrequency ablation (RFA) have emerged as minimally invasive treatment alternatives. The authors of this report performed a comparative meta-analysis evaluating cryoablation and RFA as primary treatment for SRMs.

METHODS

A search of the MEDLINE database was performed reviewing the world literature for clinically localized renal masses treated by cryoablation or RFA.

RESULTS

Forty-seven studies representing 1375 kidney lesions treated by cryoablation or RFA were analyzed. No differences were detected between ablation modalities with regard to mean patient age (P = .17), tumor size (P = .12), or duration of follow-up (P = .53). Pretreatment biopsy was performed more often for cryoablated lesions (82.3%) than for RFA (62.2%; P < .0001). Unknown pathology occurred at a significantly higher rate for SRMs that underwent RFA (40.4%) versus cryoablation (24.5%; P < .0001). Repeat ablation was performed more often after RFA (8.5% vs 1.3%; P < .0001), and the rates of local tumor progression were significantly higher for RFA (12.9% vs 5.2%; P < .0001) compared with cryoablation. The higher incidence of local tumor progression was found to be correlated significantly with treatment by RFA on univariate analysis (P = .001) and on multivariate regression analysis (P = .003). Metastasis was reported less frequently for cryoablation (1.0%) versus RFA (2.5%; P = .06). Cryoablation usually was performed laparoscopically (65%), whereas 94% of lesions that were treated with RFA were approached percutaneously.

CONCLUSIONS

Ablation of SRMs is a viable strategy based on short-term oncologic outcomes. Although extended oncologic efficacy remains to be established for ablation modalities, the current data suggest that cryoablation results in fewer retreatments and improved local tumor control, and it may be associated with a lower risk of metastatic progression compared with RFA.

Histological characterisation of small renal masses and incidence of silent renal masses

With the introduction of sonographic and CT examinations, the number of small renal masses detected has increased. Benign neoplastic lesions are usually smaller than 4 cm in size, whilst the most common types of renal cell carcinomas have a mean size greater than that, but we must not forget that a significant number of small masses are renal cell carcinomas; even though the rate of benign cases increases as the diameter of the lesions decreases, therefore, size itself cannot be used to rule out a diagnostic of malignancy and often image characteristics are not enough to predict the nature of the lesion with certainty. In this case, histological confirmation must be recommended. Ideally, the histological study must be conducted on the surgical specimen, even though biopsy can be an option in selected cases.

Histopathological characteristics of localized renal cell carcinoma correlate with tumor size: a SEER analysis

PURPOSE

We determined whether a relationship exists between primary tumor size and histopathological features in cases of localized renal cancer.

MATERIALS AND METHODS

SEER data were used to create a cohort of patients who were diagnosed with localized node negative renal masses from 1988 to 2004. Nuclear grade was divided into low and high grade groups. We used a multinomial logistic model to predict the probability of nuclear grade and histological subtype with increasing primary tumor size.

RESULTS

SEER data showed that 19,932 patients with localized renal masses were evaluated. The overall nuclear grade distribution was 80% and 20% for low and high grade tumors, respectively. A multinomial logistic model revealed that the probability of a high grade tumor increased with size. For each 1 cm increase in size of a primary localized renal cell carcinoma the odds of high grade disease increased by 13% (OR 1.13, p <0.001). Multinomial models also predicted that the odds of papillary vs clear cell renal cell carcinoma decreased with tumor size. Conversely the odds of chromophobe vs clear cell renal cell carcinoma increased with increasing tumor size.

CONCLUSIONS

Most localized node negative renal cell carcinomas are low grade. Although the probability of a high grade tumor increases with size, almost 85% of renal cell carcinomas smaller than 4 cm and 70% of localized renal cell carcinomas larger than 7 cm demonstrate low nuclear grade. The probability of detecting particular histological subtypes also varies with increasing tumor size. These data suggest that many localized renal tumors can grow large locally without acquiring metastatic potential.

Predicting growth of solid renal masses under active surveillance

OBJECTIVES

The natural history and growth rates of untreated solid enhancing renal tumors is being defined through active surveillance series. Serial radiographic evaluation of patients who are not surgical candidates or refuse surgical treatment provides an opportunity to characterize the growth of untreated enhancing renal tumors. Here we evaluate factors that may help predict radiographic growth during observation.

MATERIALS AND METHODS

We reviewed our renal cancer database for enhancing renal masses that were radiographically observed for a period of at least 12 months. Variables examined included patient age, gender, lesion size on presentation, radiographic tumor characteristics, duration of active surveillance, linear growth rate, surgical pathology, development of new renal tumors, and stage progression.

RESULTS

One hundred nine patients with 124 sporadic enhancing renal tumors were identified undergoing a period of active surveillance of at least 12 months. Median patient age was 73 years (mean 69.8, range 35-87); 72% (78/109) of patients were males. Median duration of active surveillance was 26 months (mean 33.4, range 12-156). Multifocal disease was present in 9% (10/109) of patients on presentation, accounting for 20% (25/124) of all tumors. Tumor size on presentation was a median of 2.0 cm (mean 2.61, range 0.4-12.0). Overall median tumor growth rate was 0.21 cm/y (mean 0.28, range 1.4-2.47). Observed linear growth rates were independent of patient age, gender, tumor size on presentation, multifocality, and radiographic characteristics (solid versus cystic), P > 0.05. Of the patients initiating a period of active surveillance 36% (39/109) eventually underwent definitive therapy. Malignant pathology was present in 90% (35/39) of patients undergoing treatment. In patients continuing active surveillance [64% (70/109)], 2.9% (2/70) developed de novo renal lesions and 1.4% (1/70) developed metastatic disease.

CONCLUSIONS

Currently, no clinical predictors of tumor growth or disease progression have been identified, although, the risk of developing progressive disease over the short term appears low. Clinical and molecular markers of disease progression are needed prior to offering active surveillance to otherwise acceptable surgical candidates.

Tissue-based research in kidney cancer: current challenges and future directions

The past several years have seen unprecedented advances in the application of various therapeutic strategies for the treatment of patients with renal cancer. The availability of active immunotherapy, antiangiogenic therapy, and targeted therapy for this disease has brought front and center issues related to choosing the appropriate treatment for particular patient populations. It is increasingly evident that the most promising treatment selection strategies will incorporate identifying specific features of the tumor itself. To facilitate this move toward personalized medicine, it is critically important to establish some standard principles for renal cancer tissue collection, preparation, and analysis for translational research studies. In this article, we identify and discuss some critical issues related to tissue-based kidney cancer research. We focus on five major areas as follows: (a) surgical and image-guided techniques for tissue collection; (b) quality control of specimen collection, processing, storage, and review; (c) issues related to analysis of paraffin embedded tissues; (d) genomic studies; and (e) assessment of reproducibility of assays across institutions. In addition, some practical implementation strategies are proposed. Although many of the topics discussed are specific for renal cancer, several are also relevant to tissue based biomarker investigations in a broad array of malignancies.

Outcomes following partial nephrectomy by tumor size

PURPOSE

Pathological evaluation of renal tumors treated with ablative and observational therapy is often limited and renal tumor size may be the only prognostic index available. We established long-term survival in patients following partial nephrectomy according to tumor size.

MATERIALS AND METHODS

A retrospective review of our nephrectomy registry was performed to identify patients who underwent partial nephrectomy for localized (NX/N0/cM0) solid renal tumors 7 cm or less at our institution between 1970 and 2004. Overall, cancer specific, distant metastasis-free and local recurrence-free survival was estimated using the Kaplan-Meier method and stratified according to tumor size in all tumors treated and in patients with pathologically confirmed renal cell carcinoma.

RESULTS

We identified 798 patients who underwent partial nephrectomy for a 7 cm or less renal tumor. Median patient age was 63.5 years and median tumor size was 3.0 cm. Renal cell carcinoma was present in 637 tumors (80%). Overall, cancer specific, metastasis-free and local recurrence-free survival significantly decreased with each 1 cm increase in size in all tumors treated and in those with pathologically confirmed renal cell carcinoma (each p <0.05).

CONCLUSIONS

Partial nephrectomy is associated with durable cancer control in patients with renal tumors 7 cm or less, of which most represent renal cell carcinoma. Tumor size represents a valuable prognostic index in the absence of pathological evaluation of the entire tumor specimen. These results may be used for comparison against outcomes following ablative and observational therapy, for which tumor size is the only prognostic index available.

Surveillance for the management of small renal masses

Surveillance is a new management option for small renal masses (SRMs) in aged and infirm patients with short-life expectancy. The current literature on surveillance of SRM contains mostly small, retrospective studies with limited data. Imaging alone is inadequate for suggesting the aggressive potential of SRM for both diagnosis and followup. Current data suggest that a computed tomography (CT) or magnetic resonance imaging (MRI) every 3 months in the 1st year, every 6 months in the next 2 years, and every year thereafter, is appropriate for observation. The authors rather believe in active surveillance with mandatory initial and followup renal tumor biopsies than classical observation. Since not all SRMs are harmless, selection criteria for active surveillance need to be improved. In addition, there is need for larger studies in order to better outline oncological outcome and followup protocols.

Incidence of benign pathologic lesions at partial nephrectomy for presumed RCC renal masses: Japanese dual-center experience with 176 consecutive patients

OBJECTIVES

To determine the incidence of benign pathologic findings at elective partial nephrectomy for renal masses thought to be renal cell carcinoma (RCC) on preoperative imaging in Japanese patients.

METHODS

From 1993 to 2007, 176 patients (46 women and 130 men) underwent elective partial nephrectomy for presumed RCC masses in 2 Japanese centers. The mean size of the resected lesions was 2.3 cm (range 0.3-5.8). Overall, 97 and 79 patients had a renal mass of < or = 2 cm and > 2 cm, respectively. Of the 176 patients, 100%, 89%, and 32% had preoperatively undergone computed tomography, ultrasonography, and magnetic resonance imaging, respectively.

RESULTS

Of the 176 masses resected, the pathologic examination revealed benign findings in 19 (11%), angiomyolipoma in 10 (5.7%), oncocytoma in 5 (2.8%), complicated cysts in 2 (1.1%), and a solitary fibrous tumor and scar of the kidney 1 each (0.6%). Of the 46 women, 12 (26.1%) had benign lesions compared with 7 of the 130 men (5.3%; P = .0003). Of the 10 angiomyolipomas diagnosed, 8 were diagnosed in women (P = .0004). Tumor size was not associated with benign histologic findings. The incidence of benign lesions was equivalent (10% and 12%) between the 2 centers.

CONCLUSIONS

The present incidence (11%) of benign lesions in presumed RCC masses at surgery in Japanese patients was lower than the incidence of 20%-30% previously reported from Western countries, probably because of the low incidence of oncocytomas in Japanese patients. Women had almost 5 times the likelihood of having a benign lesion compared with men, because of the high incidence of angiomyolipomas in women.

Long-term oncological and overall outcomes of percutaneous radio frequency ablation in high risk surgical patients with a solitary small renal mass

PURPOSE

We present long-term outcomes in patients receiving RFA for solitary small renal masses.

MATERIALS AND METHODS

We reviewed the overall oncological and survival outcomes of patients with a solitary renal mass treated with radio frequency ablation in whom it had been at least 40 months since treatment. Patients were offered radio frequency ablation due to the high risk of surgical management and surgeon preference. Followup consisted of serum creatinine measurement, physical examination and serial contrast enhanced computerized tomography or magnetic resonance imaging.

RESULTS

The 31 patients received a total of 34 radio frequency ablation treatments to a 1.0 to 4.0 cm solitary renal mass (median 2.0). Mean followup in survivors was 61.6 months (median 62.4, range 41 to 80). There was 1 primary treatment failure, which was successfully retreated. There were 3 recurrences 7, 13 and 31 months after radio frequency ablation, respectively. The overall recurrence-free survival rate was 90.3%. There was a 100% metastasis-free and disease specific survival rate in the cohort. Overall patient survival was 71.0% since 9 died of nonrenal cell carcinoma causes. Of the 31 patients 18 had pathologically confirmed renal cell carcinoma. In these 18 cases the actuarial disease specific, metastasis-free, recurrence-free and overall survival rates were 100%, 100%, 79.9% and 58.3%, respectively, at a mean of 57.4 months of followup. In the entire cohort the difference between the pretreatment and the last known serum creatinine level was 0.15 mg/dl (p = 0.06).

CONCLUSIONS

In patients who have limited life expectancy or are high risk surgical candidates radio frequency ablation provides reasonable long-term oncological control and it may have a role in the management of small renal masses. Meticulous long-term followup is required in patients receiving radio frequency ablation.

Active surveillance of renal masses in elderly patients

PURPOSE

We identify and report on a large number of patients treated with active surveillance for incidentally diagnosed renal masses at our institution.

MATERIALS AND METHODS

We identified all patients 75 years or older evaluated in our department for a renal mass between January 2000 and December 2006. A total of 110 patients with enhancing renal masses were initially treated with active surveillance and this group made up the cohort for our study. Medical records were reviewed for clinical and radiological followup, and vital status was obtained from the Social Security Death Index. Clinical and radiographic followup was available for review on 104 and 89 patients, respectively.

RESULTS

Patients had a median age of 81 years (range 76 to 95) with a median Charlson comorbidity index of 2 (range 0 to 7) at diagnosis. Patients had as many as 9 tumors being followed (median of 1) with a median tumor size of 2.5 cm (range 0.9 to 11.2). During a median followup of 24 months (range 1 to 90) mean tumor growth rate was 0.26 cm per year. Of the 89 patients with radiological followup 38 (43%) exhibited no tumor growth on active surveillance. Comparison of the clinical and radiographic features of patients with tumor growth and those with stable disease revealed no statistical differences. Four patients (3.6%) were treated as a result of disease progression 12 to 54 months after diagnosis. At the conclusion of the study 34 patients (31%) were deceased. To our knowledge the renal mass did not contribute to the cause of death in any patient.

CONCLUSIONS

Active surveillance of incidental renal masses appears to be a viable option for older patients with multiple medical comorbidities and a limited life expectancy.

Watchful waiting for small renal masses

Small renal masses (SRMs; < 4 cm in diameter) account for most renal tumors treated today. Incidental early detection of SRMs by abdominal imaging results in favorable grade and stage migration to renal cell carcinoma, and also increases detection of benign renal tumors. As a result, most SRMs manifest indolent biological behavior with excellent prognosis. Despite the increased use of minimally invasive laparoscopic surgery, nephron-sparing techniques, and percutaneous ablation therapy, selected patients are managed by initial active surveillance, reserving therapy for progression. Older patients and those with competing risks due to medical comorbidities are excellent candidates for active surveillance; their risk of early progression due to growth or metastases appears to be low. Active surveillance should not be recommended for younger, healthier patients until prognostic factors are better defined. Needle core use for improved histopathologic characterization of SRMs should be considered before recommending treatment.

Decreasing size at diagnosis of stage 1 renal cell carcinoma: analysis from the National Cancer Data Base, 1993 to 2004

PURPOSE

The proportion of renal cell carcinoma cases diagnosed at stage I is known to be increasing significantly. We characterized stage I tumors further in terms of tumor size at diagnosis using a large national cancer registry.

MATERIALS AND METHODS

The National Cancer Data Base captures approximately 75% of all newly diagnosed cancer cases in the United States. The database was queried for all adults who were diagnosed between 1993 and 2004 with stage I renal cell carcinoma. Trends were assessed in mean size with time as well as in the proportion of stage I tumors diagnosed at less than 2.0, less than 2.5 and less than 3.0 cm.

RESULTS

There were 104,150 patients in the National Cancer Data Base diagnosed with stage I renal cell carcinoma during the study period. A total of 10,279 stage I tumors (9.9%) were less than 2.0 cm, 26,621 (25.6%) were 2.5 cm or less and 39,879 (38.3%) were 3.0 cm or less. Analysis of stage I renal cell carcinoma diagnoses with time demonstrated a statistically significant increase in the proportion of renal masses 3.0 cm or less between 1993 and 2004 (32.5% vs 43.4%). Of tumors 3.0 cm or less the proportion smaller than 2.0 cm increased significantly during the study period from 24.1% in 1993 to 29.4% in 2004. Mean tumor size decreased from 4.1 to 3.6 cm between 1993 and 2004 (p <0.001).

CONCLUSIONS

Tumor size at diagnosis is decreasing with time in patients with stage I renal cell carcinoma. These data likely underestimate the proportion of all enhancing renal masses diagnosed at a small size. Patients with small masses may be appropriate candidates for nephron sparing surgery, energy based ablative therapy or active surveillance. Better technologies are needed to determine the diagnosis and prognosis of small enhancing renal masses.