Abstract P1-11-11: HER2-directed therapy in early breast cancer – improvement over 20 years
Authors: Thomssen Christoph , Engel Julia , Reinhardt Kristin , Strauß Hans-Georg , Große Regina , Barrot Susanne , Bauer Marcus , van Uden Lisa , Kaufhold Sandy , Schüler Kathleen , Wieder Vanessa , Kantelhardt Eva J. , Vetter Martina 
Published: March 2023

Introduction: HER2-positive breast cancer is considered aggressive, but due to the development of targeted drugs in the past 20 years, a substantial improvement of therapy results can be postulated. Proven evidence is provided by data of randomized clinical trials. The present study aimed at demonstrating the improvement of therapy results over time using single-center real world data.

Material and Methods: In our center, we prospectively built a consecutive tumor and data base from 2000 to 2020 and identified patients with early HER2-positive breast cancer (n=396). The cohort was divided in four groups by year of diagnosis according to the changing therapy concepts: A) 2000-2004 (no HER2-directed therapy, n=83), B) 2005-2011 (trastuzumab, n=96), C) 2012-2017 (trastuzumab/pertuzumab, n=135), D) 2018-2020 (T-DM1 in patients with non-pCR), n=55). HER2 was measured by IHC and ISH corresponding to the ASCO-CAP guidelines. HER2-directed therapy was indicated according to the respective national guidelines (AGO). The median follow-up was 58 months in the entire cohort (1-266), group A 84 months (10-266), group B 94 months (2-201), group C 56 months (1-118), group D 32 months (8-53). The primary endpoint was overall survival (OS), and secondary endpoint was iDFS. Kaplan-Meier estimates were calculated and multivariate analyses were performed using SPSS 28 (IBM, Armonk, NY, USA).

Results: Overall, 57% of the 396 patients had an age of 50 years or more, 85% had a NST histology, 54% of the tumors were larger than 2cm, 45% were node-positive; 34% were steroid hormone receptor negative. HER2-directed therapy was delivered to 7 of 83 pts in group A (8.4%), to 62 of 96 pts in group B (64.6%), to 119 of 135 in group C (88.15%), and to 50 of 55 pts in group D (90.91%), resp.. Overall, in the first 3 years we observed 19 deaths and the probability for OS was 89.7 % for group A, 92.2 % for group B, 96.4 % for group C and 100% for group D, resp.; iDFS was 77.4% in A, 86.8% in B, 94.9% in C and 95.2% in D, resp.. After adjustment for nodal status, grading and steroid hormone receptor status, we calculated the effect size of the incremental improvement of treatment for OS and iDFS as HRs referred to group A (Table 1).

Conclusion: With this prospectively established single center cohort, we are able to confirm a significant improvement of the treatment results in patients with HER2-positive early breast cancer over the last 20 years applying individualized HER2-directed therapies.

Table 1. Multivariate analyses of OS and iDFS adjusted for nodal status, grading and hormone receptor status.

Citation Format: Christoph Thomssen, Julia Engel, Kristin Reinhardt, Hans-Georg Strauß, Regina Große, Susanne Barrot, Marcus Bauer, Lisa van Uden, Sandy Kaufhold, Kathleen Schüler, Vanessa Wieder, Eva J. Kantelhardt, Martina Vetter. HER2-directed therapy in early breast cancer – improvement over 20 years [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 P1-11-11.