Microsimulation modeling of alternate surveillance strategies in renal oncocytoma: Practical considerations for...

Use of renal mass biopsy (RMB) has increased, leading to more diagnoses of renal oncocytoma. Although benign, diagnostic uncertainty and the absence of clear size thresholds for intervention complicate management. We used microsimulation modeling to evaluate surgical, oncologic, and cost outcomes of liberalizing intervention thresholds for biopsy-proven oncocytoma while accounting for biopsy misclassification.

Fifteen-year microsimulation (10,000 patients per iteration) compared absolute size thresholds from 4 to 9 cm for intervention in surgically fit patients undergoing annual surveillance. Tumor growth was modeled using a PERT distribution (mean 0.16 cm/y). Misclassification and metastasis probabilities were derived from published data. Outcomes included rates of surgery, complications, metastasis, and total cost. Sensitivity analyses varied biopsy diagnostic certainty from 75% to 95%.

At a 4 cm threshold, 83% underwent surgery over 15 years compared with 59% at 5 cm and 36% at 6 cm, and 31% at ≥7 cm. Increasing the threshold reduced serious complications from 2.2% to 0.9% at 9 cm and readmissions from 2.1% to 0.6% as percentage of patients surveilled. Percent of patients developing an estimated glomerular filtration rate < 45 decreased from ∼17% at 4 cm to ∼6% at 7-9 cm. Mean cost was similar across pathways ($41,025-$46,889). With 75% diagnostic certainty, metastasis ranged from 1.4% to 2.3% across thresholds; at ≥90% certainty, metastasis was <1% for all strategies.

The risk of progression to surgery decreases over 15 years as surgeons increase the intervention threshold. As the threshold increases, perioperative risks to patients progressing decrease, along with the risk of CKD driven primarily by the increased rate of nonintervention over the long term. Despite diagnostic uncertainty, the risk of metastasis on surveillance is very low.