Hormone Receptor-Negative Breast Cancers Gain Greatest Economic Benefit from Trastuzumab

The cost-effectiveness of adjuvant trastuzumab (Herceptin, Genentech) may vary based on patient age and disease subtype among women with HER2-positive breast cancer, according to study results published in PLoS Medicine.

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Clinicians should account for clinical heterogeneity and patient differences when allocating and funding treatment with adjuvant trastuzumab, according to the researchers.

Trastuzumab is a monoclonal antibody that binds to the HER2 protein, which is expressed on up to 25% of breast cancers. Women with HER2-positive breast cancer often face worse outcomes, largely due to disease resistance to standard chemotherapies. Current clinical practice guidelines recommend that women meeting left ventricular ejection fraction guidelines receive a 12-month course of trastuzumab following anthracycline therapy; however, costs associated with trastuzumab are significantly higher than standard chemotherapeutic regimens, and no prior study has evaluated the cost-effectiveness of its use based on hormone receptor status.

William Leung, MSc, lecturer in health economics at University of Otago (Wellington, New Zealand), and colleagues performed a cost-utility analysis of landmark randomized controlled trials to determine the cost-effectiveness of trastuzumab vs chemotherapy based on patient age, estrogen receptor (ER) status, and progesterone receptor (PR) status. The researchers determined incremental cost-effectiveness ratios (ICERs), incremental quality-adjusted life-years (QALYs) and costs based on each individual hormone receptor subtype, with valued pooled together by 5-year age increments, from 25 to 29 years to 90 to 94 years. The age group of 50 to 54 years served as the median age group for the base case.

The researchers observed that patients with ER- or PR-negative breast cancer gained twice the benefit from adjuvant trastuzumab than patients with more favorable disease subtypes (incremental QALYs for patients aged 50-54 years, 2.33; 95% CI, 2.29-2.37). Cost-effectiveness was primarily mitigated based gains in QALYS, rather than age or subtype; ICERs ranged from approximately $45,000 for patients with ER- and PR-negative disease to $100,000 for patients with ER- and PR-positive disease.

Using a willingness-to-pay threshold of $45,000 per QALY gained, the researchers found trastuzumab cost-effective for women with ER- and PR-negative breast cancers up to the age of 69 years, which represented 37% of included cases. However, at a willingness-to-pay threshold of $90,000 per QALY, trastuzumab resulted in lower rates of cost-effectiveness among women with ER-negative breast cancer subtypes aged between 70 to 79 years, as well as women with ER-positive disease aged up to 70 years.

Study limitations identified by the researchers included the lack of treatment-effect data based on hormone receptor subgroup and the restriction of the heterogeneity analysis to age and disease subtype, without including tumor size or tumor grade.

“The patent on Herceptin expired in 2014 in the EU and will expire in the U.S. in 2019,” wrote Mr  Leung and colleagues. “Although a trastuzumab biosimilar has not yet been approved via the EU centralized procedure, reduced-cost trastuzumab biosimilars (Hertraz from Mylan and Herzuma from Celltrion) have been approved in other jurisdictions, and several other pharmaceutical companies have trastuzumab biosimilars in the pipeline. While the expected lower cost of biosimilars may make trastuzumab more cost-effective in previously less viable patient subgroups, cost pressures are likely to continue as new treatments are being trialled for HER2-positive early breast cancer patients.”