Contribution of trastuzumab to the prognostic improvement of HER2-positive early breast cancer in Spain: an estimation of life years and disease-free life years gained since its approval

Introduction: Trastuzumab has become the standard treatment for both HER2-positive early and metastatic breast cancer (HER2+ eBC or mBC) since its approval. The objective of the study is to estimate the benefit of adjuvant trastuzumab in the treatment of patients with HER2+ eBC in terms of life years gained (LYG) and disease-free life years gained (DFLYG) since its approval in Spain in 2006. Results: 35,851 women make up the cohorts from 2006 to 2017. In the T (trastuzumab)+CT (chemotherapy) scenario, the sum of life years was 605,358 (525,964 disease-free) versus 564,137 (489,916 disease-free) in the CT scenario, resulting in 41,221 LYG (36,048 disease-free) due to trastuzumab. The general population for the same age range would have generated 704,331 LY. The estimated incremental cost was 880.43 million€ (€24,558.13 per patient) from 2006 to 2035. The incremental cost-effectiveness ratios obtained were €20,644 and €23,960 per LYG and DFLYG, respectively. Methods: An epidemiological model was developed with a time horizon until 2035 and a 3% discount rate. The model compared two scenarios, with and without trastuzumab as adjuvant therapy. The effectiveness data to model the survival curves were obtained from BCIRG 006 study and direct costs were included. Conclusions: Adjuvant trastuzumab has substantially improved the survival of patients with HER2+ eBC, contributing over 41,000 LYG to Spanish society (over 36,000 DFLYG) in a cost-effective manner. However, the sum of LYG with trastuzumab is still far from the LY estimated for the general population, supporting the need of further advances in HER2+ eBC.