Abstract P3-02-05: Interim Analysis Results from a European Disease Registry Study Aimed to Prospectively Observe Treatment Patterns and Outcomes in Patients with HER2+ Unresectable Locally Advanced or Metastatic Breast Cancer
Authors: Balic Marija , Costa Luis , Ojaimi Joseline , Oprean Cristina Marinela , Coelho José L. Passos , Pazos Isabel , Puglisi Fabio , Sanglier Thibaut , Scandurra Giuseppa , Schenker Michael , Wahyudi Laurentia A. , Zhbantov Georgi , Timcheva Constanta 
Published: March 2023

BACKGROUND: Metastatic breast cancer (MBC) is incurable, with the primary goal of treatment being to extend survival while preserving quality of life. Treatment options available to patients (pts) with human epidermal growth factor receptor-2 positive breast cancer (HER2+ BC) may vary between countries, in terms of both the drugs used and the sequence in which they are used. There is limited data available on the clinical characteristics and outcomes in pts with unresectable locally advanced (LA) BC. This study aimed to capture real-world data on treatment patterns and clinical outcomes in HER2+ unresectable LABC and MBC.

METHODS: SAMANTHA (NCT02913456) is an ongoing, prospective, multicentre non-interventional study designed to observe pts with HER2+ unresectable LABC or MBC for a period of up to 8 years on study. The primary objectives are progression-free survival (PFS), assessed according to standard medical practice, and the treatment received. Secondary objectives included overall survival (OS), duration of response and safety. This pre-planned interim analysis reports baseline characteristics, treatment regimens received, first-line (1L) PFS by advanced BC status and the incidence of adverse events (AEs).

RESULTS: The study enrolled 647 pts from five European (EU) countries (Nov 2016-Nov 2019); 629 received 1L treatment and were included in data analysis. At data cut-off date (16 Nov 2021), median follow-up on study was 30.4 months (mo; range: 0.1; 60.0); 342 (54%) pts discontinued 1L treatments, of whom 170 (50%) pts received 2L treatments, 74 pts died, 49 pts were lost to follow-up, 35 pts withdrew consent and 14 pts withdrew due to physician decision. The full analysis set (FAS) included 222 (35%) LABC pts and 407 (65%) MBC pts [Table]. Pertuzumab/trastuzumab based regimens were given as 1L in the majority of pts [462 (73 %)]. The FAS Median (m) PFS in 1L was 41.3 mo (95% CI: 36.1, 54.1) for LABC and 23.5 mo (95% CI: 20.6, 27.6) for MBC. Median OS was not reached. In the FAS, any AEs were reported in 352 (56%) pts; of these 212 (34%) had a grade 3 or higher AE. Serious (S) AEs were reported in 135 (22%) pts; of whom, 36 (6%) pts had treatment related SAEs.

CONCLUSIONS: This interim analysis of SAMANTHA provides a snapshot of LABC/MBC treatment practices in five EU countries, where pertuzumab/trastuzumab based regimens appear to be the most used 1L treatment options, which aligns with the recommended standard of care. The mPFS is consistent with previous literature although higher than what was reported in the pivotal clinical trial CLEOPATRA. Given the good outcome observed in 1L and the current follow-up period of 30.4 mo, the data are not yet mature enough to provide complete insights into the treatment sequencing patterns and the clinical outcomes associated with these treatments.

Acknowledgments: The study is sponsored by F. Hoffmann-La Roche Ltd.

Table: Demographics and baseline disease characteristics of patients by status of advanced BC

Citation Format: Marija Balic, Luis Costa, Joseline Ojaimi, Cristina Marinela Oprean, José L. Passos Coelho, Isabel Pazos, Fabio Puglisi, Thibaut Sanglier, Giuseppa Scandurra, Michael Schenker, Laurentia A. Wahyudi, Georgi Zhbantov, Constanta Timcheva. Interim Analysis Results from a European Disease Registry Study Aimed to Prospectively Observe Treatment Patterns and Outcomes in Patients with HER2+ Unresectable Locally Advanced or Metastatic Breast Cancer [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P3-02-05.