Cost-effectiveness of zoledronic acid and strontium-89 as bone protecting treatments in addition to chemotherapy in patients with metastatic castrate-refractory prostate cancer. (ISRCTN 12808747) TRAPEZE

Background: Bony metastatic CRPC has a poor prognosis and high morbidity. TRAPEZE is a factorial RCT using 3 agents, docetaxel (D), zoledronic acid (ZA) and strontium-89 (Sr89). All have palliative benefits and are used in bony metastatic CRPC to control bone symptoms. This study aims to assess the cost-effectiveness of adding bone-protecting treatments—zoledronic acid (ZA) and strontium-89 (Sr89)—to docetaxel chemotherapy for patients with castrate-refractory prostate cancer (CRPC). Methods: Data on resource use and health outcomes collected prospectively in the TRAPEZE 2x2 factorial trial were used to compare the cost-effectiveness of ZA vs. no ZA, and Sr89 vs. no Sr89. Costs are estimated from the NHS perspective. Outcomes are expressed as quality-adjusted life-years (QALYs) and cost-effectiveness is presented as incremental cost per additional QALY. Results: Based on the availability of generic zoledronic acid, the per-patient cost for ZA was £12,667, £251 (95% CIs: -£1,099 to £1,602) higher than the equivalent value in the no ZA group. Patients in the ZA group experienced on average 0.03 QALYs (95% CIs: -0.07 to 0.13) more than their counterparts in no ZA. The incremental cost-effectiveness ratio (ICER) for this comparison was £8,005. A higher ICER of £42,047 was found when using the price of branded zoledronic acid. Sr89 was associated with a cost of £13,230, £1,365 (95% CIs: -£12 to £2,742) higher than no Sr89. The Sr89 group showed a gain of 0.08 QALYs (95% CIs: -0.02 to 0.18) over no Sr89. The ICER for Sr89 was estimated at £16,884. Conclusions: ZA was associated with a modest additional cost and a slight improvement in QALYs, resulting in an ICER well below the conventional threshold of £20,000 per QALY. Given the availability of generic zoledronic acid at a low cost, ZA appears to be a beneficial option for both CRPC patients and the NHS. Sr89 resulted in an ICER of less than £20,000; nonetheless it is unclear whether findings will prove practice-changing in light of competition from newer radioisotopes. Clinical trial information: 12808747.