Abstract P6-17-24: Use of subcutaneous and intravenous trastuzumab: Real-world experience from three hospitals in Sweden
Authors: Valachis A , Carlsson L , Sundqvist M , Li B , Chiesa F , Uhde M , Sanglier T 
Published: May 2019

Abstract
Background
Trastuzumab (H; F. Hoffmann-La Roche Ltd, Basel, CH) reduces recurrence and improves survival in patients (pts) with HER2-positive early breast cancer (EBC). Two formulations which are noninferior in terms of pathologic complete response and serum trough concentration (Ismael et al. Lancet Oncol 2012) are available, for intravenous (IV) and subcutaneous (SC) administration. A randomized open-label study, PrefHer, reported compelling pt preference for H SC (Pivot et al. Lancet Oncol 2013; Ann Oncol 2014), and a prospective observational study reported less societal cost and pt time associated with H SC vs H IV in Sweden (Olofsson et al. Breast 2016), which may allow for earlier release of pts from hospital. To assess how this may translate to actual practice, we aimed to describe H SC and H IV use in a real-world setting and investigated a potential switch from one formulation to the other in the real world.
Methods
This observational, retrospective, longitudinal cohort study evaluated electronic medical records of adult female pts with a first incident diagnosis of EBC (neoadjuvant or adjuvant settings) and first use of H from 01/01/10–04/24/18 in three mid-size hospitals in Sweden (Sundsvall, Eskilstuna, and Kalmar). Data from first H administration (index date) until last recorded visit up to the day before metastasis (if any) were analyzed. Combination anticancer treatment was defined as any drug recorded from index date to index date +28 days. A switch between formulations was defined as any H administration using a formulation different from that given at the index date.
Results
Four hundred twenty-one pts received initial H (median age 60.2 years, range 23.3–88.5). Of these, 260 (61.8%) started treatment with H SC and 161 (38.2%) with H IV. After H SC was introduced in Nov 2013, use of H SC as the initial formulation increased from 72.7% in 2014 to 100% in 2017 (Table). Both H SC and H IV were mostly initiated with a combination IV chemotherapy e.g., a taxane (65.8% vs 74.5%, respectively). Some combination pertuzumab (F. Hoffmann-La Roche Ltd) was observed (2.3% vs 1.9%). Since 2013, 40 of 63 pts (63.5%) switched from initial H IV to H SC; ten (25.0%) switched back to H IV. Four of 260 pts (1.5%) switched from H SC to H IV; three (75.0%) switched back to H SC.
H SC n=260H IV n=161Calendar year of the index date, n (%/year) 2010021 (100)2011026 (100)2012051 (100)20131 (3.7)26 (96.3)201448 (72.7)18 (27.3)201555 (79.7)14 (20.3)201677 (93.9)5 (6.1)201772 (100)0 (0)20187 (100)0 (0)Combination anticancer treatment, n (% of all) Taxanes171 (65.8)120 (74.5)Anthracyclines5 (1.9)1 (0.6)Pertuzumab6 (2.3)3 (1.9)Other (platinum salts, metabolites, other cytotoxic/cytostatic agents)11 (4.2)4 (2.5)
Conclusion
H SC quickly became the prevailing (practically exclusive) formulation for treatment of pts with HER2-positive EBC. Furthermore, most pts who started on H IV switched to H SC, while a minority switched from H SC to H IV. Most pts also received similar combination IV treatment (e.g., pertuzumab or chemotherapy) regardless of H formulation. Results are in line with pt preference for H SC in the PrefHer study, and the body of evidence that oncology units switch to SC formulations of biologics as an integral part of routine care.
Citation Format: Valachis A, Carlsson L, Sundqvist M, Li B, Chiesa F, Uhde M, Sanglier T. Use of subcutaneous and intravenous trastuzumab: Real-world experience from three hospitals in Sweden [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P6-17-24.