Cost effectiveness of risk-prediction tools in selecting patients for immediate post-prostatectomy treatment.

BACKGROUND AND OBJECTIVE

Ideally, tests that predict the risk of cancer recurrence should be capable of guiding treatment decisions that are both therapeutically effective and cost effective. This paper evaluates the cost effectiveness of two tools that identify patients at high risk for biochemical (prostate-specific antigen) recurrence of prostate cancer after prostatectomy, the hypothesis being that accurate classification of high-risk patients will allow more appropriate use of secondary (adjuvant/salvage) treatment and may improve on current clinical practice. These risk-prediction tools are the Kattan postoperative nomogram, which uses clinicopathologic features, and the Prostate Px test, which employs additional morphometric and immunofluorescence features of the prostate specimen to predict risk of biochemical recurrence. These tools were trained on patients treated at the Memorial Sloan-Kettering Cancer Center (996 patients for the nomogram, 342 patients for the Prostate Px test).

METHODS

The cost effectiveness of the Prostate Px test, the Kattan postoperative nomogram, and current clinical practice were compared using a decision analytic model. The modeled treatment for low-risk patients was watchful waiting. The modeled treatments for high-risk patients were local radiation, hormonal therapy, and watchful waiting. Costs, utilities, and transition probabilities were obtained from the literature. Costs and effects were discounted at 3% per year. The time span modeled was 10 years after prostatectomy. Monte Carlo simulation was performed to estimate cost and effectiveness; sensitivity analysis was performed to examine the impact of uncertainty in the parameter values.

RESULTS

The expected quality-adjusted life years (QALYs) for the Prostate Px test, nomogram, and current practice were 8.11, 7.39, and 6.47, respectively. The expected costs were $US17 549, $US14 162, and $US14 104, respectively. The incremental cost-effectiveness ratio of the Prostate Px was $US4704/QALY compared with the nomogram, and $US2100/QALY compared with current practice. The incremental cost-effectiveness ratio of the nomogram was $US63/QALY compared with current practice. These ratios are well below the common willingness-to-pay limit of $US50 000/QALY. Expected effectiveness was highest for the Prostate Px test, followed by the nomogram. Expected cost was slightly higher for Prostate Px than for either alternative; nevertheless, the Prostate Px was cost effective compared with both the nomogram and current practice. The nomogram was cost effective compared with current practice. The acceptable cost effectiveness of the Prostate Px test and the nomogram compared with current practice were not sensitive to changes in the values used to inform the model within clinically plausible ranges. The superior performance of both Prostate Px test and nomogram over current practice resulted from identifying high-risk patients likely to benefit from adjuvant treatment, while sparing the low-risk patients the added cost and toxicity of treatment.

CONCLUSION

Incorporation of risk-prediction tools in the initial management of patients after prostatectomy resulted in increased QALYs at an acceptable increase in cost relative to current practice.