JU INSIGHT: Pediatric Small Renal Masses: Can Tumor Size Help Predict Histology?

By: Daniel S. Han, MD, Stanford University School of Medicine and Lucile Packard Children’s Hospital, Palo Alto, California; Jonathan P. Walker, MD, University of Tennessee College of Medicine Chattanooga; Andrew Nicklawsky, MS, University of Colorado Cancer Center, Aurora; Peter Boxley, BA, University of Colorado School of Medicine and Children’s Hospital Colorado, Aurora; N. Valeska Halstead, MD, University of Colorado School of Medicine and Children’s Hospital Colorado, Aurora; Michael Tonzi, MD, University of Tennessee College of Medicine Chattanooga; Sarah L. Hecht, MD, Oregon Health and Sciences University, Portland; Alyse Staley, MS, University of Colorado Cancer Center, Aurora; Megan Eguchi, MPH, University of Colorado Cancer Center, Aurora; Myles G. Cockburn, PhD, University of Southern California, Keck School of Medicine, Los Angeles; Jonathan P. Roach, MD, Surgical Oncology Program of the Children’s Hospital Colorado, Aurora; Amanda F. Saltzman, MD, University of Kentucky College of Medicine, Lexington; Nicholas G. Cost, MD, University of Colorado Cancer Center, Aurora University of Colorado School of Medicine and Children’s Hospital Colorado, Aurora Surgical Oncology Program of the Children’s Hospital Colorado, Aurora | Posted on: 17 Mar 2023

Han DS, Walker JP, Nicklawsky A, et al. Pediatric small renal masses: can tumor size predict histology and the potential for nephron-sparing surgery? J Urol. 2023;209(3):582-590.

Study Need and Importance

Radical nephrectomy (RN) is the standard of care for surgical resection in children with nonsyndromic unilateral renal masses (uRMs) suspicious for malignancy. Nephron-sparing surgery (NSS) in children is generally reserved for those with bilateral Wilms tumor (WT), predisposition syndromes, a solitary kidney, or select non-WT histologies.

In this study, we evaluated the utility of preoperative radiographic tumor size as a clinical factor to determine the probability of finding WT on final pathology for children with uRMs. We hypothesized that pediatric small renal masses, defined as tumors <4 cm, are more likely to have benign/intermediate or other non-WT histologies that may be potentially appropriate for NSS.

What We Found

In the SEER (Surveillance, Epidemiology, and End Results) database analysis, tumors ≥4 cm had higher odds of being WT compared to tumors <4 cm. After age stratification, it was observed that this predictive relationship was driven by patients 5-9 years of age. In the institutional analysis, tumors ≥4 cm had higher odds of being WT (vs non-WT), malignant (vs benign), and of having RN appropriate histology (vs NSS appropriate histology; see Table).

Table. Institutional Analysis: Logistic Regression Models for Outcomes of Interest

Variable	Wilms tumor status, odds ratio (P value; 95% CI)	Malignant vs benign, odds ratio (P value; 95% CI)	Radical nephrectomy vs nephron-sparing surgery appropriateness, odds ratio (P value; 95% CI)
Tumor size
<4 cm	Reference	Reference	Reference
≥4 cm	30.85 (.001; 3.75, 254.1)	6.75 (.005; 1.76, 25.93)	46.79 (< .001; 5.61, 390.1)
Abbreviation: CI, conﬁdence interval.

Limitations

Limitations included the study’s retrospective nature and single-institution origin of the institutional data. Additionally, there was a relatively low number of patients in the institutional data with a unilateral renal mass <4 cm. Finally, there are well-known limitations of SEER-based research, including: variability in data reporting, limited information on treatment and tumor characteristics, and error-rates of clinical research databases.

Interpretation for Patient Care

A pediatric renal tumor size cut point of 4 cm was helpful in predicting WT, malignancy, and RN-appropriate histology. Renal tumor size should be considered as an additional factor during clinical decision-making for the surgical management of pediatric uRMs.