Renal cancer. Contemporary management. Editor John A. Libertino. Springer New York 2013.
Renal cell carcinoma (RCC) is the most common primary malignancy of the kidney, and it is the most lethal of all urologic malignancies. Close to 60,000 men and women were diagnosed with RCC in 2011, and the mortality rate of RCC has been and continues to be close to 25% [1, 2]. Due to the increased use of cross-sectional abdominal imaging over the past several decades, a stage migration towards low-grade low-stage RCC has been observed in large population-based cohorts [3, 4]. In the decade from 1993 to 2004, the proportion of new RCC cases diagnosed at stage I increased from approximately 43–57%, and the incidence of tumors less than 3.0 cm in diameter at presentation increased from 32.5 to 43.4% (Фиг. 8.1). Today, the vast majority of small renal masses (SRMs) are discovered incidentally, are asymptomatic, and have a variable malignant potential. Approximately 15% of SRMs are benign tumors, and only an estimated 20–30% of RCC cases are determined by pathologic assessment to have features suggestive for potentially aggressive biology and behavior [9, 10].
Concurrent with the increasing incidence in SRMs, a concurrent “age migration” of RCC has been observed, with SRMs more frequently identiﬁed in patients of increasing median age, with a peak rise in incidence in persons between 70 and 90 years of age. Paradoxically, although the rates of renal surgery and other interventions have risen as well, the mortality from RCC has not improved over the last decades, suggesting that the absolute number of lethal lesions has not diminished. Many believe this observation indicates that a large proportion of SRMs may be clinically insigniﬁcant benign or indolent tumors and that extirpation of all SRMs may represent overdiagnosis and overtreatment.
The concept of overdiagnosis and overtreatment of malignancy is a relatively new concern. The risks and consequences associated with unneeded treatment for low-risk or indolent cancers are potentially the most important and underappreciated harms associated with early cancer detection. While stage I RCCs are suggested to be one of the most “curable” urologic malignancies, whereas surgical treatment for stage I RCC demonstrates 5-year cancer-speciﬁc survival rates in excess of 95%, some have begun to question if the driving force behind these favorable outcomes is simply indolent intrinsic tumor biology rather than treatment effect. Further, there is a growing recognition that the competing risks to survival from medical comorbidities may outweigh the expected beneﬁt of intervention on a SRMs in elderly and/or inﬁrmed patients.
Фиг. 8.1. Число случаев почечно-клеточной карциномы стадии I (1993-2004), стратифицированное по объему опухоли (<3 см или ≥3 см)
One clear example of this idea is reﬂected in the evolution of the management of prostate cancer. Over the past 25 years, the development and aggressive utilization of PSA-based prostate cancer screening in the United States has also resulted in a signiﬁcant stage migration. The great majority of prostate cancer diagnoses care currently made in asymptomatic men who are identiﬁed to have organ-conﬁned malignancies. Though this stage of prostate cancer can be highly successfully treated with standard therapy, the natural history of the majority of cases of untreated low-grade, early-stage prostate cancer is understood to progress along a relatively long and indolent course, and most men with prostate cancer will likely die of other causes and not from their disease. From this observation was born the management approach of “watchful waiting,” especially for men of advanced age having prostate cancer and substantial concurrent comorbidity, and there is the expectation that deﬁnitive treatment of prostate cancer in that scenario provides marginal beneﬁt. Recognizing that low-volume, low-grade prostate cancer might behave in an indolent manner for decades, the concept of expectant management with serial reassessment and possible delayed intervention (active surveillance (AS) with curative intent) has also been further extended and applied to younger or healthier men. This approach has the intent of proceeding with curative treatment only in the event of a change in the predicted prostate cancer behavior or in its perceived risk. This practice of AS defers immediate intervention to avoid the potential morbidities of treatment until evidence of increased clinical risk is identiﬁed, at which time curative treatment can still be applied and its impact is then justiﬁed. Limited longterm data supports the AS management approach for selected men with prostate cancer , and similarly, AS has been applied in select patients with SRMs and signiﬁcant competing risks. Although limited by small cohorts and retrospective methodology, the current data supporting AS for management of the incidental SRMs represents perhaps the most comprehensive observational data for any solid organ malignancy to date. In this chapter, we aim to review the natural history and malignant potential of SRMs, discuss the contemporary role of renal mass biopsy, and summarize the existing body of evidence supporting the use of AS for localized SRMs.