Surveillance vs. Surgery For Small Kidney Masses?

MedicDavid C. Johnson, MD, MPH Department of Urology University of North Carolina School of Interview with:
David C. Johnson, MD, MPH
Department of Urology
University of North Carolina School of Medicine


Medical Research: What are the main findings of the study?

Dr. Johnson: 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 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 US 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 from this study was 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 approach 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 which were most likely to be benign. We found 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 US.

Medical Research: Were any of the findings unexpected?

Dr. Johnson: We found that rates of benign pathology in surgical series outside of the US were substantially lower those of the US studies. This presents an interesting area for future investigation into the reasons behind this disparity.

Medical Research: What should clinicians and patients take away from your report?

Dr. Johnson: 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 are 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 their 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.

Medical Research: What recommendations do you have for future research as a result of this study?

Dr. Johnson: We plan 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.


Preoperatively Misclassified, Surgically Removed Benign Renal Masses: A Systematic Review of Surgical Series and United States Population-Level Burden Estimate

David C. Johnson, Josip Vukina, Angela B. Smith, Anne-Marie Meyer, Stephanie B. Wheeler, Tzy-Mey Kuo, Hung-Jui Tan, Michael E. Woods, Mathew C. Raynor, Eric M. Wallen, Raj S. Pruthi, Matthew E. Nielsen


Publication stage: In Press Accepted Manuscript

Published online: July 26, 2014


Last Updated on July 29, 2014 by Marie Benz MD FAAD