Growth rates of renal cell carcinoma and oncocytoma under surveillance are similar

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.

Understanding the relationship between health care quality and the renal mass

Quality is increasingly important to all stakeholders of the U.S. health care system. Endeavors to measure and improve quality have moved forward in cardiovascular disease, diabetes care, and surgical wound infections. However, in urology, such efforts have lagged. As a specialty, we are now faced with pressures, exerted primarily by payors, to roll out performance measures, or quality indicators, in the absence of science to support them. In this review, we discuss the broad concepts of health care quality and describe their relationships with small renal tumors.

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.

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.

Distribution of renal tumor growth rates determined by using serial volumetric CT measurements

PURPOSE

To retrospectively determine the distribution of growth rates across different sizes and subtypes of renal cortical tumors by assessing tumor volume and maximum tumor diameter at serial volumetric computed tomographic (CT) examinations.

MATERIALS AND METHODS

The institutional review board approved this retrospective, HIPAA-compliant study. Fifty-three of 2304 patients (34 men, 19 women; mean age, 67 years +/- 10 [standard deviation; range, 39-88 years) who underwent nephrectomy from 1989 to 2006 did not receive preoperative chemotherapy or radiation therapy and underwent at least two preoperative contrast material-enhanced CT examinations (at least 3 months apart) with identical section thickness that was no more than one-fifth of longitudinal tumor diameter. Tumor volume and maximum diameter were measured on CT scans. Reciprocal of doubling time (DT) (RDT) was calculated. Analysis of variance and Student t tests were performed.

RESULTS

Thirty-two clear cell carcinomas, 10 papillary carcinomas, six chromophobe carcinomas, four oncocytomas, and one angiomyolipoma were analyzed. Median tumor size was 2.9 cm (range, 1-12 cm). Seven tumors did not increase in volume. DT ranged from -78476.54 to 18057.43 days (mean, -1230.73 days; median, 590.51 days). [corrected] Growth rate determined by using maximum diameter ranged from -10.8 to 33.2 mm/y (mean, 5.1 mm/y; median, 3.5 mm/y). Faster-growing tumors were more likely to be clear cell carcinomas, those of higher grade had higher growth rates. No significant correlation was found between RDT and tumor initial volume, subtype, or grade. Small renal tumors (<or=3.5 cm) were similar to larger tumors in subtype and growth rate. Age at diagnosis correlated negatively with renal tumor growth rate (P = .03).

CONCLUSION

Growth rates in renal tumors of different sizes, subtypes, and grades represent a wide range and overlap substantially. Small renal tumors appear to be similar to larger ones in nature.

Clonal expansion of mutated mitochondrial DNA is associated with tumor formation and complex I deficiency in the benign renal oncocytoma

Mutations in mitochondrial DNA (mtDNA) are frequent in cancers but it is not yet clearly established whether they are modifier events involved in cancer progression or whether they are a consequence of tumorigenesis. Here we show a benign tumor type in which mtDNA mutations that lead to complex I (CI) enzyme deficiency are found in all tumors and are the only genetic alteration detected. Actually renal oncocytomas are homogeneous tumors characterized by dense accumulation of mitochondria and we had found that they are deficient in electron transport chain complex I (CI, NADH-ubiquinone oxidoreductase). In this work total sequencing of mtDNA showed that 9/9 tumors harbored point mutations in mtDNA, seven in CI genes, one in complex III, and one in the control region. 7/8 mutations were somatic. All tumors were somatically deficient for CI. The clonal amplification of mutated mtDNA in 8/9 tumors demonstrates that these alterations are selected and therefore favor or trigger growth. No nuclear DNA rearrangement was detected beside mtDNA defects. We hypothesize that functional deficiency of the oxidative phosphorylation CI could create a loop of amplification of mitochondria during cell division, impair substrates oxidation and increase intermediary metabolites availability.