Renal Mass Biopsy Is Associated With Fewer Radical Nephrectomies for Benign or Indolent Disease, Particularly for T1b...

How renal mass biopsy (RMB) impacts patient management with T1 renal masses (T1RMs) is unclear. We explore the association between RMB and utilization of active surveillance (AS), nephron-sparing interventions, and radical nephrectomy (RN).

Data were analyzed retrospectively using the MUSIC-KIDNEY (Michigan Urological Surgery Improvement Collaborative Kidney Mass: Identifying and Defining Necessary Evaluation and Therapy) registry. Treatment received was analyzed using a fitted mixed-effects multinomial logistic-regression model.

Of 4062 patients, 19.6% underwent RMB. Factors associated with RMB included younger age, higher Charlson comorbidity score, tumor size > 2.0 cm, and higher complexity tumors. AS was selected by 88%, 68%, and 27% of patients with benign, indeterminate, and malignant RMB findings. Nonmalignant pathology at surgery was significantly (P < .0001) more common without RMB (vs after RMB), ie, 14.8% vs 7.2% of PN and 10.2% vs 1.7% of RN. In patients with T1bRM managed without vs with RMB, AS was chosen by 22% vs 34%, nephron-sparing interventions by 31% vs 35%, and RN by 47% vs 32% (P = .0027). An interaction between tumor stage (T1a vs T1b) and RMB remained in multivariable analyses accounting for practice-level variation and other confounding variables. The risk-adjusted RN rate for T1bRM was 41.4% without RMB vs 27.8% with RMB; 7.4 RMBs are needed to avoid 1 RN (number needed to treat) for benign or indolent disease.

Treatments received by T1RM patients undergoing RMB are different than when RMB is omitted, based on RMB results and several confounders. T1RM patients benefit from reduction in intervention for nonmalignant disease, particularly when RN is planned. For every 7 biopsies of T1bRM performed, 1 RN was avoided.