Cost-utility of adjuvant trastuzumab in Her-2/neu positive breast cancer: A Canadian perspective

6574 Background: Recent RCTs have demonstrated a significant disease-free and overall survival advantage with adjuvant trastuzumab (aTZ) compared to chemotherapy alone in women with Her2/neu positive breast cancer. However, as aTZ is also associated with considerable costs and an increased risk of cardiotoxicity, an economic evaluation was undertaken to estimate the cost-utility (CU) of aTZ in terms of cost per quality-adjusted life year (QALY) gained relative to chemotherapy alone. Methods: A Markov model was developed to calculate the incremental costs and outcomes of 12 months of aTZ following chemotherapy in a hypothetical cohort of 1,000 women with Her2/neu positive breast cancer over a lifetime horizon. The model consisted of four broad health states: 1) disease-free, 2) local recurrence, 3) distant recurrence and 4) death. Each survival state was stratified as experienced with or without cardiotoxicity. The baseline rate of recurrence, the hazard ratio (HR) of recurrence with aTZ and the rate of adverse cardiac events were taken from recent RCTs. Age-sex specific background mortality, based on Statistics Canada life tables, was also incorporated. The cost of aTZ was based on our previous cost study (Drucker et al, ASCO 2006). Costs of local and distant cancer recurrence were derived from the literature, with an adjustment for the cost of palliative TZ (Potvin et al, ASCO 2005). Utility weights were taken from the literature. The model took a direct payer perspective, with costs reported in 2006 Canadian dollars (CDN$). Costs and QALYs were both discounted by 3% annually. The primary analysis assumed 5 years of benefit with aTZ therapy and an HR=1.0 over the remainder of the horizon. Results: Per 1,000 treated patients, aTZ was associated with a lifetime gain of 1,267 QALYs and an incremental cost of CDN$38.8 million. Lifetime CU was CDN$30,630 per QALY gained. aTZ met a CDN$50,000/QALY threshold at year 17. CU results were particularly sensitive to changes in the analysis horizon and assumptions regarding the long-term HR of aTZ. Conclusions: The lifetime CU of aTZ appears reasonable. However, further clinical follow-up is required to clarify the long-term outcomes of aTZ and confirm these CU estimates. No significant financial relationships to disclose.

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