Poster Presentation Clinical Oncology Society of Australia Annual Scientific Meeting 2023

Background: Trastuzumab, a recombinant antibody targeting HER2 is a gold standard for treatment of

HER2-positive breast cancer. However, cost-related factors impede trastuzumab use in 12 - 54 %

patients. The current study assessed the outcomes of 437 HER2 neu +ve breast cancer patients who

received trastuzumab.

Methodology: Data of patients treated between September 2006 and July 2018 was analyzed. The primary endpoint was overall survival (OS) and secondary endpoint was event-free survival (EFS) and safety. Survival outcomes in the study were compared with historical data.

Results: The median age was 55 years. Out of 437, seventy five were positive for estrogen receptor and sixty were positive for progesterone receptor. In this study 194 patients (44.39 %) had cancer in right

breast and 242(55.37%) had cancer in left breast and one had bilateral breast cancer. 3.49 percent had family history of breast cancer.

While 240 patients received trastuzumab in adjuvant setting, 197 patients received neoadjuvant

trastuzumab. Median OS Median EFS is shown in the table.

Mean baseline ejection fraction was 59.42. Post treatment mean ejection fraction was 57.32. Although

the mean post-treatment ejection fraction was lower after trastuzumab, only 13 patients had to

discontinue trastuzumab because of drop in ejection fraction to less than 45. Other adverse events

were generally mild and were of grades 1-2. In the subset analysis there was no difference in the safety

and efficacy parameters between the different brands of trastuzumab used in the study.

Conclusion: In the present study, the median OS and event free survival rates with both adjuvant and neoadjuvant trastuzumab are comparable with data from historical studies. Safety in terms of ejection fraction was not a concern in the study.