Abstract P2-13-06: Long term clinical follow up of real world HER2-positive patients since the introduction of trastuzumab

Background: The prognosis for patients with HER2-positive early breast cancer (EBC) has improved dramatically since the introduction of adjuvant trastuzumab therapy. With the addition of pertuzumab the prognosis has improved further. However, there is a need to study how these results from clinical controlled trials are transferred to the real-world clinical setting. In this study we aim to investigate all patients with early HER2-positive breast cancer in our region since the introduction of adjuvant trastuzumab to evaluate the implementation of trastuzumab treatment regarding treatment coverage, prognosis and survival. Method: All patients with HER2-positve EBC, diagnosed between 2006 and 2014 in South-east Sweden were included in the study. The patients were identified using the Swedish national breast cancer register and then cross-referenced with data from the pathology department at each hospital in order to obtain complete coverage in a retrospective clinical follow up. In addition, data were collected from medical records for each patient to verify the actual given treatments and survival data. Results: Preliminary data is available. 611 patients were included with a median follow-up time of 5 years. During the follow-up period the number of patients diagnosed with HER2-positive EBC cancer doubled. 73% of all patients received trastuzumab treatment; however the coverage increased successively from 56% in 2006 to 83% in 2013. ER-positive patients did receive trastuzumab therapy to the same extent as ER-negative patients. Local recurrence-free survival (LRFS), distant recurrence-free survival (DRFS) and breast cancer specific survival (BCSS) at 5 years were 85%, 76%, and 75% for patients not receiving trastuzumab. In the trastuzumab treated group LRFS, DRFS and BCSS was 95%, 85% and 83% respectively. The group not receiving trastuzumab was significantly older, had more frequently node negative disease and was not treated with chemotherapy to the same extent. Conclusion: A significant amount of early HER2-positive breast cancer patients did not receive adjuvant trastuzumab therapy between 2006 and 2014. In this group fewer patients received chemotherapy and despite less nodal involvement LRFS, DRFS and BCSS were poor for these patients. Citation Format: Ellegard S, Asowed M, Engvall K, Hallbeck A-L, Elander N, Stal O. Long term clinical follow up of real world HER2-positive patients since the introduction of trastuzumab [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 P2-13-06.