ACTIVE SURVEILLANCE VERSUS INITIAL NEPHRON-SPARING TREATMENT FOR SMALL RENAL TUMORS: A DECISION ANALYSIS

Purpose: Small, incidentally detected renal tumors most often have low potential for metastatic progression.  Nevertheless, the standard treatment is surgery, specifically partial nephrectomy (PN). Surgery may have deleterious clinical consequences, particularly for patients with chronic kidney disease (CKD), including renal function decline and worsened overall survival. Alternate management strategies include imaging-based active surveillance (AS), biopsy, and ablation, which offer greater renal function preservation but poorer cancer control. We compared life expectancies (LE) across surgical and alternate renal tumor treatment strategies to identify the optimal treatment in the setting of variable CKD and comorbidity status. 

Method: A state-transition microsimulation model was used to compare LE for: 1) PN for all; 2) Ablation instead of PN for stage 2 or 3a CKD and complex tumor anatomy, or stage 3b CKD and any tumor anatomy; 3) Biopsy, with triage of cancers to ablation or PN based on CKD and tumor anatomy; and 4) AS. The model incorporated tumor anatomic complexity (predictive of post-surgical renal functional loss), renal functional decline, mortality rates by CKD stage, comorbidities, benign and malignant tumors, and risk of cancer progression. Patients were susceptible to all-cause, surgical, and cancer-specific mortality. Relative to PN, less invasive treatment strategies were associated with fewer complications and greater preservation of renal function. Sensitivity analysis was performed to test the stability of results with parameter variability. 

Result: Biopsy was the most favorable strategy overall, driven by treatment of fewer benign tumors than with empiric treatment, and sparing of some patients worsened CKD and mortality risks associated with PN. The LE advantage of biopsy was more pronounced in stage 3 CKD: for example, in stage 3a CKD, biopsy LE was +2.6 years compared to AS, +2.2 years versus uniform PN, and +0.47 years compared to selective ablation. In frail patients with Charlson comorbidity index of at least 1 and stage 3b CKD, AS was less effective than biopsy (-0.40 years) but superior to PN (+0.50 years). Results were most sensitive to rates of renal function decline and related mortality.

Conclusion: Renal tumor biopsy likely offers the most effective management in patients with stage 2 or 3 CKD and at least moderately complex tumor anatomy. However, patients with CKD stage 3b and other medical comorbidities benefit only modestly from biopsy compared with AS.