A systematic review of surgical series and United States population-level burden estimate of preoperatively misclassified, surgically-removed benign renal masses, "Beyond the Abstract," by David C. Johnson, MD, MPH

BERKELEY, CA (UroToday.com) - The first main finding from this study is that the likelihood of benign pathology after surgical removal of a renal mass, suspected to be malignant based on pre-operative evaluation, is inversely proportionate to size. This concept is well established, however we systematically reviewed the literature for surgical series that published rates of benign pathology stratified by size and combined these rates to determine a single pooled estimate of benign pathology of pre-operatively suspicious renal masses for each size strata. Using benign pathology rates from U.S. studies only, we found that 40.4% of masses < 1 cm, 20.9% of masses 1-2 cm, 19.6% of masses 2-3 cm, 17.2% of masses 3-4 cm, 9.2% of masses 4-7 cm, and 6.4% of masses > 7 cm are benign.

The more novel finding is the quantification of a previously unmeasured burden of over treatment in kidney cancer. By combining the above-mentioned rates of benign pathology with epidemiological data, we estimated that the overall burden of benign renal masses surgically removed in the US to approached 6,000 per year in 2009. This represented an 82% increase over the course of a decade. Most importantly, we found an overwhelmingly disproportionate rise in the surgical treatment of renal masses in the smallest size categories – those most likely to be benign. We estimated a 233%, 189% and 128% increase in surgically removed benign renal lesions < 1 cm, 1-2 cm, and 2-3 cm, respectively, from 2000 – 2009 in the U.S.

This report is intended to examine a previously unquantified dimension of over treatment and encourage discussion on the existing paradigm of surgical removal of renal masses without tissue diagnosis. Despite improvements in the diagnostic ability of renal mass biopsy and increased comfort with ablative techniques and active surveillance, particularly in elderly and/or poor surgical candidates, our study demonstrates that there is still a staggering increase in surgical treatment for the smallest of renal masses – of which a large proportion are benign.

While the surgical removal of benign renal masses presents a large and growing public health problem, the challenge of managing a radiographically suspicious small renal mass is not lost on the authors. These population-level estimates do not take into account individual preferences, emotions, and circumstances that lead to surgical removal of small renal masses. For example, many years of active surveillance and serial imaging in a young patient who is anxious about his small renal mass is not necessarily the right management option for this patient. Our results should be taken into consideration when making individual treatment decisions, but are primarily intended to elucidate the scope of a unique, previously unquantified phenomenon from a public health perspective.

Our group plans to evaluate the economic burden and down-stream health effects related to the surgical resection of benign renal lesions to further characterize this dimension of over treatment in subsequent studies. More generally, continued efforts are needed to further refine the diagnostic ability of renal mass biopsy and pre-operative imaging to reduce this burden of surgically removed benign renal masses. Molecular techniques have recently shown promise in distinguishing between benign and malignant pathology and warrant continued investigation. Significant efforts to characterize the natural history of small renal masses and evaluate competing risks in older patients and those with multiple medical comorbidities have made active surveillance an appealing consideration in this population. Further research into the risks, benefits, and patient-centered outcomes of this strategy are necessary.

Written by:
David C. Johnson, MD, MPH as part of Beyond the Abstract on UroToday.com. This initiative offers a method of publishing for the professional urology community. Authors are given an opportunity to expand on the circumstances, limitations etc... of their research by referencing the published abstract.

PGY-4, Department of Urology University of North Carolina, Chapel Hill, NC USA

Preoperatively misclassified, surgically removed benign renal masses: A systematic review of surgical series and United States population-level burden estimate - Abstract

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