Abstract P1-09-05: Re-Testing of HER2 Status in Recurring Metastatic Breast Cancer Is a Clinically Relevant and Cost-Effective Strategy

Abstract

Abstract Introduction Previously HER2 status has been shown to change in 6 to 30% of recurring metastatic breast cancer (RMBC) patients (pts). Still most clinicians base trastuzumab (TZ) re-treatment decisions on prior HER2 testing of the primary tumor. This study investigates cost-effectiveness of re-testing of HER2 status (REHER) of metastasis in RMBC pts before TZ treatment in a Swedish setting. Materials and methods A Markov state transition model is used to simulate six different strategies for REHER and treatment of RMBC. The analysis is performed for two cohorts with different patient management and resource use, based on: I Treatment guidelines and published data on the patient group (guideline cohort, GC); II Clinical practice with real life data from a Swedish breast cancer database (real life cohort, RLC). Quality adjusted life year (QALY) weights and risks of progression and breast cancer death are taken from literature. Outcomes are measured as QALYs gained and costs, including both direct and indirect costs. Analyses are performed with life time perspective and both costs and outcomes are discounted at 3%. Costs have been converted to USD with an exchange rate of 7.367 SEK/USD. Testing and treatment strategies. Results Chemotherapy alone for all pts (strategy 0) is least costly and results in 1.309 QALYs gained. IHC testing all pts and treat FISH confirmed IHC 2+ 3+ pts with TZ (strategy 4) has lowest incremental cost-effectiveness ratio (ICER), $63,200 and $61,100 for GC and RLC respectively. FISH testing all pts and treating FISH+ with TZ (strategy 5) is the most efficient strategy resulting in 1.543 QALYs gained with an ICER at $75,500 and $73,300 respectively. Strategies 1 and 3 are dominated by simple dominance (less expensive alternative with better outcome). Strategy 2 is dominated by extended dominance (alternative with better effectiveness and lower ICER). Results for guideline and real life cohorts. Conclusion The cost of patient management calculated based on guidelines is similar to the one based on observed clinical practice. RLC is less costly but both cohorts give the same ranking of strategies. A Swedish study estimated willingness to pay (wtp) in Sweden to 88,900 $/QALY gained. If TZ treatment is an option REHER of metastasis is clinically relevant and cost-effective. Depending on the wtp strategies 4 and 5 can be considered. Interesting to notice is that strategy 1 (no re-testing of metastasis), probably the most common one used, is dominated and thus suboptimal regardless of wtp per QALY. Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P1-09-05.