PD06-06: Is Adjuvant Trastuzumab Economically Justified in Her-2/neu Positive T1bNO Breast Cancer?

Abstract Background: A number of clinical trials and cost-utility analyses of adjuvant trastuzumab (aTZ) for Her-2/neu positive breast cancer suggest favourable efficacy and safety along with acceptable cost-effectiveness. These evaluations, however, were based on patient cohorts with moderate-to-high risk disease, including node positive or high risk node negative disease with tumor sizes greater than 1cm (≥T1cN0). The role of aTZ for patients with lower risk disease, such as T1bN0, remains unclear in light of the varying 10-year relapse risks (10-30%) reported to date. Objective: To estimate the cost-utility of chemotherapy plus aTZ versus chemotherapy alone in Her-2/neu positive breast cancer patients with lower recurrence risk in terms of cost per quality-adjusted life year (QALY) gained. Methods: A state-transition economic model was developed to estimate the incremental costs and quality-adjusted life year (QALY) gains associated with a strategy of chemotherapy plus aTZ relative to chemotherapy alone over a 25-year analysis horizon. The model consisted of four broad health states, stratified with or without cardiotoxicity: 1) disease-free, 2) local recurrence, 3) distant recurrence and 4) death. Given the variability in reported risk estimates for T1bN0 disease, a range of 10-year baseline recurrence risks (10-30%) in the absence of chemotherapy or aTZ was examined. The clinical benefit of chemotherapy was assumed to differ according to age (<50 vs. ≥50 years). The hazard ratio of recurrence with aTZ (HR=0.64) and the rate of associated adverse cardiac events were derived primarily from the HERA clinical trial. Utility weights and the costs of local and distant cancer recurrence were derived from the literature, while the costs of adjuvant and palliative TZ were derived from our previous work. The model took a direct payer perspective, with costs reported in 2011 Canadian dollars (CDN$). Costs and QALYs were both discounted by 3% annually. The reference analysis assumed 3 years of clinical benefit from chemptherapy and aTZ. A series of one-way sensitivity analyses tested the impact of longer benefit as well as the impacts of measuring outcomes in terms life years rather than QALYs, a lifetime analysis horizon and different HRs. Results: The reference analysis observed that the cost per QALY gained was greater than CDN$100,000 across the entire range of recurrence risks tested. One-way sensitivity analyses observed that considering life years rather than QALYs, a lifetime analysis horizon, extending the duration of benefit to 5 years or improving the HR to 0.54 each did little to improve the overall economic favorability of aTZ, even at the higher range of recurrence risk. Conclusions: The cost-utility of adjuvant trastuzumab appears unfavourable in Her-2/neu positive breast cancers with a baseline 10-year relapse risk of less than 30% without treatments, such as in T1bN0 disease. Specific estimates of cost-utility await more precise estimates of the recurrence risk in patients with T1bN0 disease. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr PD06-06.

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