Original article
Declining incidence of benign lesions among small renal masses treated with surgery: Effect of diagnostic tests for characterization

https://doi.org/10.1016/j.urolonc.2018.05.001Get rights and content

Highlights

  • We evaluated the changes in the incidence of benign lesions in SRMs.

  • The incidence of benign histology for SRMs declined during recent years.

  • The recent increased use of RMB might be associated with the decreased incidence.

Abstract

Purpose

We evaluated the changes in the incidence of benign lesions in surgically removed small renal masses (SRMs) and the effect of diagnostic tests for characterizing SRMs.

Methods

We included 2,707 patients receiving surgery for SRMs (<4 cm). Trends in the incidence of benign histology were evaluated according to the surgery year (period 1: 2001–2005, 2: 2006–2010, and 3: 2011–2015). Multivariable logistic regression analysis was performed to identify factors associated with benign lesions. Additionally, the number of surgeries prevented due to benign histological findings on renal mass biopsies (RMB) done on 206 patients with SRM during study period was evaluated.

Results

Benign histology was identified in 192 (7.1%) patients. Incidence of benign histology was 9.7%, 7.0%, and 6.3% for period 1, 2 and 3, respectively. The uses of multiphase computed tomography and magnetic resonance imaging were more common in periods 2 and 3 than in period 1 (P<0.001). The use of RMB in period 3 was higher than in periods 1 and 2 (0.8 vs. 0.9 vs. 9.0%, P<0.001). In multivariable analysis, older age, male sex, larger tumor size, and recent surgery year (period 3 vs. 1, odds ratio = 0.62, P = 0.028) were independently associated with decreased odds of benign lesions. The number of prevented surgeries by performing RMB was 0, 10, and 39 in periods 1, 2, and 3, respectively.

Conclusions

Incidence of benign histology after surgery for SRMs declined during recent years, which might be associated with the recent increased use of RMB.

Introduction

With the increased use of cross-sectional imaging modalities, the incidence of localized renal cell carcinoma (RCC) has been increasing during the last 3 decades, with the greatest increase observed in small renal masses (SRMs), usually defined as having a radiological diameter of<4 cm [1], [2], [3]. However, at the same time, the incidence of benign histology in surgical specimens has increased as the size of renal masses has decreased, even in renal masses suspected to be RCC on preoperative diagnostic examinations [4].

In the current clinical guidelines, contrast-enhanced multiphase computed tomography (CT) is considered the most reliable radiologic examination for characterizing renal masses before surgery [5]. However, the characteristics of some renal tumors remained indeterminate even with multiphase CT [6]. Because surgery for benign renal tumors is generally considered nonbeneficial [7], [8], recent imaging studies and renal mass biopsy (RMB) have been widely used to identify histologic characteristics before definitive management; magnetic resonance (MR) imaging has been reported to be an effective method for distinguishing angiomyolipomas (AML) from RCC [9] and percutaneous RMB has shown high diagnostic accuracy for distinguishing benign lesions from RCC with a tolerable rate of complications [2], [10]. Despite imaging or tissue acquisition suggesting a benign result, a fair number of patients still undergo surgery for their SRM [8], [11], [12], [13].

As mentioned earlier, variable imaging studies and RMB have been widely used to identify tumor histology before definitive management, and these efforts may have impacted trends in the incidence of benign lesions after surgery for SRM over time. However, to our knowledge, no studies have been conducted to elucidate this issue because multiple factors (i.e., level of evidence, cost, insurance system in each country, etc.) could affect the use of diagnostic tests for SRMs. We thereby sought to evaluate the changes in the incidence of benign lesions in SRMs by surgery year, which might reflect the change in diagnostic tests used, with a large cohort of patients with SRMs during the past 15 years.

Section snippets

Patient cohort

A total of 2,707 patients who underwent curative surgery for SRMs (<4 cm) at our institute from January 2001 to December 2015, including 683 patients who underwent radical nephrectomy and 2,024 patients who underwent partial nephrectomy, were included in this study. Diagnostic procedures and surgical methods performed in the 2,707 patients are depicted in the Fig. The electronic medical records of these patients were retrospectively reviewed to retrieve the detailed demographic and clinical

Results

Of 2,707 patients, benign histology was identified in 192 (7.1%) patients. Among 192 patients with benign lesions, oncocytoma was identified in 71 patients (37.0%), AML in 79 patients (41.1%), and other benign lesions in 42 patients (21.9%). Among cases with malignant histology, clear cell RCC was detected in 2,065 patients (82.1%), papillary RCC in 209 patients (8.3%), chromophobe RCC in 169 patients (6.7%), and other malignant lesions in 72 patients (2.9%).

The uses of multiphase CT (84.3%,

Discussion

To avoid unnecessary surgeries for misclassified benign renal masses, clinicians generally make every effort to distinguish benign renal masses from RCC. However, a considerable number of surgeries are still performed for benign renal masses owing to preoperatively misclassified lesions [4], [19], [20]. This problem is believed to be more serious than before because the size of renal masses becomes smaller as the incidence of incidentally detected renal masses has increased over time [21].

Conclusions

Our study showed that in a large cohort of patients receiving curative surgery for SRMs, the incidence of benign histology after surgery for SRMs has declined in recent years. The recent increased use of RMB, in addition to the effect of evolving imaging techniques and implanting MRI, might be associated with the decreased incidence of benign histology. In the future, a large population-based study will be needed to assess the effects of these diagnostic tests on the incidence of benign

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