Kidney CancerAge-Adjusted Incidence, Mortality, and Survival Rates of Stage-Specific Renal Cell Carcinoma in North America: A Trend Analysis
Introduction
Kidney cancer accounts for approximately 4.0% of cancer incidence and 2.3% of cancer morality in the United States, with an estimated 57 760 new cases and 12 980 new deaths as of 2009 [1]. Most adult kidney cancers that originate from the renal parenchyma are renal cell carcinomas (RCCs). The incidence of RCC has varied significantly over the last two decades worldwide [2], [3], [4], [5]. In general, incidence rates of RCC are higher among men and persons of African American descent [4], [5], [6].
Due to the widespread use of cross-sectional imaging in contemporary practices, incidental diagnoses of small renal masses have become frequent radiologic findings [7]. In temporal trend analyses, RCC stage-specific incidence rates support this observation, where the greatest increase across RCC tumor stages over time are among stage I (localized) tumors [2], [4], [5], [6]. Trend analyses in survival have also improved over time [4], [5].
Although these results are highly encouraging, it may be argued that measures of incidence and/or survival may not be enough to indicate progress against RCC. The reported incidence of a disease may often merely reflect changing patterns in diagnosis and increasing activity of screening [8], [9], [10], [11]. Similarly, survival rates may also be flawed due to the inclusion of patients with less malignant and benign tumors, which creates a lead-time bias [8], [9], [10], [11].
Several investigators support the use of age-adjusted mortality rates as a basic measure of progress against cancer [2], [5], [8], [9], [10], [11], [12]. Existing trend analyses reporting on mortality rates for RCC are scarce. Those who have reported detected an important increase in mortality rates over time [2]. Unfortunately, a crucial oversight in the selection criteria of that study may have precluded the relevance of their findings [13]. Other investigators also examined the mortality rates and reported an increase across all race and sex groups over time [5]. However, the study period covered in that study (1975–1995) is outdated.
To address the limitations just described, we sought to reevaluate the age-adjusted incidence, mortality, and 5-yr survival rates of stage-specific RCC in North America using the Surveillance Epidemiology and End Results (SEER) database of the National Cancer Institute (NCI) program.
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Patient population
Relying on 17 registries from the SEER database, we identified persons diagnosed with renal cell carcinoma from 1988 to 2006. The SEER database, as part of the NCI program, routinely collects patient demographics and publishes cancer incidence and survival data from population-based cancer registries covering approximately 10% of the US population up to the year 2000, and 26% from that time on [14].
The study included histologically confirmed cases of invasive cancers of the kidney parenchyma or
Results
From 1988 to 2006, 43 807 cases of RCC were identified within 17 SEER registries (Table 1). Overall, 27 185 (62.1%) were men and 16 622 (37.9%) were women. A total of 26 490 RCC cases (60.5%) were localized versus 8181 (18.7%) regional and 9136 (20.9%) distant. The prevalence of localized RCC rose from 1988 to 2006 (51.2–70.8%). Conversely, the prevalence of regional stages (20.9–13.6%) and distant stages (27.9–15.6%) declined for the same time points.
The overall RCC age-adjusted incidence rate
Discussion
Previous studies demonstrated an increase in the incidence of RCC and attributed it to the result of increasing incidentally detected tumors [2], [4], [5], [6]. Indeed, with the increase in the use of cross-sectional imaging, small renal masses have become common radiologic findings [18]. It is estimated that approximately 13–27% of abdominal imaging studies incidentally identify a renal lesion [19], [20]. Most of these lesions represent small cysts that do not require any treatment. With the
Conclusions
Taken together, our findings strongly indicate changes in the diagnosis of RCC over time. Unfortunately, the rising incidence was not accompanied by decreasing mortality rates over time. Although RCC is detected at an earlier stage, early treatment efficacy was not shown. Future age-adjusted analyses on RCC incidence and mortality rates are needed to confirm or refute the current trends.
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Both authors contributed equally.