Influence of renal biopsy results on the management of small kidney cancers in older patients: Results from a population-based cohort.

BACKGROUND AND OBJECTIVE: Small kidney cancers are a heterogeneous group with varying malignant potential. Pathologic information obtained from a renal biopsy may guide decision-making for small kidney cancers. We sought to assess the effect of pathologic information from renal biopsy on the nonsurgical management of small kidney cancers in a population-based cohort of patients over 65 years of age.

METHODS: In the Surveillance, Epidemiology and End Results-Medicare dataset, we identified patients ≥66 years diagnosed with a kidney cancer<4cm between 2002 and 2011. Diagnostic biopsy was defined by a Medicare claim within 1 month prior through 6 months following cancer diagnosis or before surgery. Nonsurgical management was defined by the absence of a claim for partial or radical nephrectomy or tumor ablation in the first 6 months following diagnosis. The relationship between patient and tumor characteristics and the likelihood of nonsurgical management by receipt of diagnostic biopsy was assessed by multivariable logistic regression models.

RESULTS: From 8,933 patients, 2,782 (31%) had a diagnostic renal biopsy of whom 616 (22%) were managed nonsurgically. Controlling for patient, disease, and provider specialty, biopsy was associated with nonsurgical management (adjusted odds ratio = 1.61, 95% Cl: 1.43-1.82) in patients with low-grade tumors but also with more aggressive histology (clear cell renal cell carcinoma). Older age (85+) and geographic region were significantly associated with greater odds of diagnostic biopsy. Patients whose initial renal tumor diagnosis was made by a urologist (vs. other type of provider) were less likely to receive a biopsy (adjust odds ratio = 0.73, 95% Cl: 0.60-0.89).

CONCLUSIONS: Although the use of renal biopsy has increased over time and is associated with the use of nonsurgical management of small kidney cancers, the use of the pathologic findings remains limited. Further advances, particularly with prognostic markers, are necessary before renal biopsy can be routinely implemented for treatment decision-making for small kidney cancers.