Regional variation in CT imaging is associated with nephrectomy risk

1. Regional variation in cumulative risk of an individual having a chest or abdominal CT in the United States was positively correlated with the risk of both total and partial nephrectomy, as well as any renal procedure (including renal ablation).

2. This association may reflect incidental detection and over-diagnosis of renal masses, with an increased frequency of procedures.

Evidence Rating Level: 2 (Good)

Study Rundown: In an effort to determine the impact of incidental findings from CT imaging, the authors determined the cumulative risk of having either a chest or abdominal CT over a 5-year period, as well as the risk for partial or total nephrectomy or renal ablation in hospital referral regions (HRRs) across the United States. Kidney cancer is commonly diagnosed from an incidentally detected renal mass on CT, with some cases never causing symptoms. The frequency of renal procedures may be indicative of the frequency of over-diagnosis. The authors found that imaging risk varied from 31% to 52% across the country, and that imaging risk positively correlated with the risk of both partial and total nephrectomy, with a stronger association to any nephrectomy and with addition of renal ablation to the procedures under consideration. These associations remained even after controlling for adult smoking rates.

Since the data is observational, a causative effect cannot be concluded. Another potential confounder is the intensity of medical care in the geographical region; however, the authors eliminate this as a confounder by showing no association between imaging risk and radical prostatectomy, a procedure unrelated to incidental CT detection. This study has implications for the appropriateness of ordering CT imaging as well as the importance of discussing with patients the potential risk of incidental findings from CT imaging. Furthermore, given the risk of complications from renal procedures, these results argue for thorough consideration of active surveillance as an option for the treatment of renal masses.

Click to read the study, published in JAMA Internal Medicine

Relevant Reading: Small renal masses in the elderly: Contemporary treatment approaches and comparative oncological outcomes of nonsurgical and surgical strategies.

In-Depth [cross-sectional study]: This study determined the correlation between an individual’s 5-year cumulative risk of having either a chest or abdominal CT and an individual’s 5-year risk for partial and total nephrectomy, or alternative interventions such as radiofrequency or cryoablation. All risks were determined from Medicare claims. These correlations were determined for geographic regions across the United States, determined by 306 hospital referral regions (HRRs). The study population consisted of Medicare beneficiaries from age 65 through 85 years, which totaled to 15,513,426 beneficiaries. Imaging risk varied from 31% in Santa Cruz, California, to 52% in Sun City, Arizona. Imaging risk was positively associated with the risk of both total and partial nephrectomy (Pearson r = 0.28; p < 0.001 for both), and increased when combining the procedures (r = 0.38; 95% CI, 0.28-0.47) and when including renal ablation (r = 0.46; 95% CI, 0.37-0.54). When controlling for HRR adult smoking rates, imaging an additional 1000 beneficiaries was associated with 4 additional nephrectomies (95% CI, 3-5) or 5.5 additional renal procedures (95% CI, 4-7). Case-fatality rates for nephrectomies were 2.1% at 30 days and 4.3% at 90 days.

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