6626 Background: Trastuzumab is administered to patients with early breast cancer (EBC) whose tumors test positive for HER2 using IHC or FISH diagnostic tests. However, due to test characteristics and testing heterogeneity, patients may be misdiagnosed as false positive (FP) or false negative (FN). This analysis estimates the lifetime economic burden of inaccurate HER2 testing in the US. Methods: We developed a national-level economic model to estimate the impact on healthcare costs and quality-adjusted life years (QALYs) in both groups in 2012. The model estimates the expected number of FP and FN patients using literature-derived estimates of each test’s sensitivity, specificity, and utilization. Based on estimates from the literature, a FP patient would generate unneeded trastuzumab costs of about $56,000 and experience a chance (2.9%) of related cardiotoxicity; an FN patient would save $56,000 in trastuzumab costs, but lose 1.7 QALYs of life expectancy and face a greater likelihood of recurrence and associated costs ($42,000) to treat metastatic disease. A net monetary benefit approach (valuing healthy life years at $100,000) is used to compare the lifetime economic burden for FP and FN. Results: The estimated overall proportions of FP and FN are 2.8% and 2.2% of 227,000 EBC patients, resulting in about 6,400 and 5,000 women in each group, respectively. Overall, approximately 8600 QALYs would be lost among FN patients who do not receive trastuzumab. We estimate the incremental per-patient lifetime burden of an FP to be about $57,000, and for an FN to be about $118,000. The implied incremental loss to society for FPs is $362 million and for FNs is $596 million. Conclusions: Current testing practices and treatment patterns for HER2+ EBC patients result in misdiagnosis and non-optimal treatment in approximately 11,500 patients each year: the combined total economic loss to society is nearly $1 billion. The greater share of the loss is among FN patients who would have benefited from trastuzumab, but did not receive it. The significant annual burden of HER2 misdiagnosis suggests that substantial societal investments to improve HER2 test accuracy should be considered.
The Lifetime Economic Burden of Inaccurate HER2 Testing: Estimating the Costs of False-Positive and False-Negative HER2 Test Results in US Patients with Early-Stage Breast Cancer
