Radiofrequency ablation versus nephron-sparing surgery for small unilateral renal cell carcinoma: cost-effectiveness analysis

Abstract

Purpose: To evaluate the relative cost-effectiveness of percutaneous radiofrequency (RF) ablation versus nephron-sparing surgery (NSS) in patients with small (<or=4-cm) renal cell carcinoma (RCC), given a commonly accepted level of societal willingness to pay.

Materials and methods: A decision-analytic Markov model was developed to estimate life expectancy and lifetime costs for 65-year-old patients with a small RCC treated with RF ablation or NSS. The model incorporated RCC presence, treatment effectiveness and costs, and short- and long-term outcomes. An incremental cost-effectiveness analysis was performed to identify treatment preference under an assumed $75,000 per quality-adjusted life-year (QALY) societal willingness-to-pay threshold level, within proposed ranges for guiding implementation of new health care interventions. The effect of changes in key parameters on strategy preference was addressed in sensitivity analysis.

Results: By using base-case assumptions, NSS yielded a minimally greater average quality-adjusted life expectancy than did RF ablation (2.5 days) but was more expensive. NSS had an incremental cost-effectiveness ratio of $1,152,529 per QALY relative to RF ablation, greatly exceeding $75,000 per QALY. Therefore, RF ablation was considered preferred and remained so if the annual probability of post-RF ablation local recurrence was up to 48% higher relative to that post-NSS. NSS preference required an estimated NSS cost reduction of $7500 or RF ablation cost increase of $6229. Results were robust to changes in most model parameters, but treatment preference was dependent on the relative probabilities of local recurrence after RF ablation and NSS, the short-term costs of both, and quality of life after NSS.

Conclusion: RF ablation was preferred over NSS for small RCC treatment at a societal willingness-to-pay threshold level of $75,000 per QALY. This result was robust to changes in most model parameters, but somewhat dependent on the relative probabilities of post-RF ablation and post-NSS local recurrence, NSS and RF ablation short-term costs, and post-NSS quality of life, factors which merit further primary investigation.

Figure 1:

Decision tree for treatment of small (≤4-cm) unilateral RCC with NSS versus RF ablation. Therapeutic strategies are shown after decision node (to right of □). Probabilistic outcome is shown after chance node (to right of ○). Terminal nodes (M) signify that Markov model informed by therapeutic effectiveness defines ensuing pathway. We assumed that 80% of tumors could be successfully ablated in one session, and that 20% of tumors would require two sessions; all tumors were considered completely ablated following two sessions. These estimates were made on basis of report of renal tumor RF ablation from our institution (10), recategorized for 4-cm or smaller RCCs.

Figure 2:

Markov model simulates outcomes for 65-year-old cohort following RCC treatment with NSS or RF ablation. Simulated cohort enters “Post-Operative” (post-NSS) or “Post-Procedure” (post–RF ablation) health state. During each 1-month cycle, part of cohort transits to states of “Local RCC Recurrence,” “Metastatic RCC,” and “Death” based on constant transition probabilities (Table 1), until all patients die of RCC or non-RCC causes. Cumulative incurred time and expenses in each health state can be summed, enabling calculation of strategy-specific life expectancy and lifetime costs.

Figure 3:

ICER of NSS relative to RF ablation versus yearly probability of local RCC recurrence after RF ablation. Given $75 000 per QALY willingness-to-pay threshold level, RF ablation was preferred at base-case estimate (probability = 0.0041 [10% higher relative to NSS]), and for probabilities less than 0.0055 (48% higher relative to NSS). For probabilities less than 0.0040 (7.1% higher relative to NSS), RF ablation dominated NSS and was associated with greater QALYs and lower expense as compared with NSS. For probabilities of 0.0055 or higher, NSS was preferred. Probability range shown corresponds to that tested in sensitivity analysis (Table 1).

Figure 4:

ICER of NSS relative to RF ablation versus age. RF ablation was considered preferred for men and women aged 45–75 years. For men aged 45–69 years and women aged 45–72 years, ICERs of NSS relative to RF ablation exceeded $75 000 per QALY willingness-to-pay threshold level. For men aged 70 years and older and women aged 73 years and older, RF ablation afforded higher quality-adjusted life expectancy at lower cost, and therefore dominated NSS.

Figure 5:

ICER of NSS relative to RF ablation versus estimated RF ablation costs. RF ablation is considered preferred at both base-case estimate of RF ablation cost ($17 589) and for estimated RF ablation cost (<$23 818). For RF ablation costs $23 818 or higher, NSS is preferred at $75 000 per QALY willingness-to-pay threshold level; for RF ablation costs of more than $24 251, NSS dominates RF ablation. Probability range shown corresponds to that tested in sensitivity analysis (Table 2). Estimated RF ablation costs are in constant 2006 dollars.