Abstract PS6-35: Real world outcomes in elderly women with HER2 positive advanced breast cancer
Authors: Evans Nicole , Anton Angelyn , Wong Rachel , Lok Sheau Wen , De Boer Richard , Malik Laeeq , Greenberg Sally , Yeo Belinda , Nott Louise , Richardson Gary , Collins Ian M , Torres Javier , Barnett Frances , Gibbs Peter , Devitt Bianca 
Published: February 2021

Abstract
BackgroundThe development of anti-human epidermal growth factor receptor 2 (HER2) therapies has significantly improved disease outcomes in patients with HER2-positive advanced breast cancer (ABC). However, elderly patients are persistently under-represented in clinical trials, with only 2.4% of patients aged ≥75 years in the pivotal CLEOPATRA study. Despite a lack of research addressing treatment outcomes in elderly patients, advanced age at diagnosis is associated with a greater likelihood of receiving no initial systemic therapy for de novo metastatic breast cancer. Studies have also shown that older women diagnosed with metastatic breast cancer have a poorer prognosis and shorter life expectancy. We examined treatment patterns and outcomes in an elderly (defined as ≥70) ‘real world’ Australian population.
MethodsData was extracted from the Treatment of Advanced Breast Cancer in the HER2-positive Australian Patient (TABITHA) multi-site clinical registry, and patients stratified according to age (&lt;70 and ≥70 years). Descriptive statistics were used to report baseline characteristics and compared using T-tests and Chi square analyses. Treatment duration and overall survival were calculated via the Kaplan-Meier method using GraphPad Prism 8.0 software.
ResultsWe identified 319 patients, including 67 patients (21%) aged ≥70 years. Older patients were more likely to have an Eastern Cooperative Oncology Group performance status of ≥2 (16% vs 3%; p&lt;0.001) and a Charlson Comorbidity Index of ≥2 (13% vs 7%; p&lt;0.001). There were no significant differences in hormone receptor status, de novo metastatic presentation, or presence of visceral disease between groups. A similar proportion of patients in each group received first line HER2-directed therapy (85% vs 93%; p=0.054), and the duration of therapy was not significantly different between groups (16 vs 22 months; p=0.70). Despite no difference between groups in the proportion of patients who received first-line chemotherapy, older patients demonstrated shorter chemotherapy durations (2.7 months vs 3.5 months; p&lt;0.02). Median overall survival was significantly longer in younger patients (82 months vs 42 months; hazard ratio, 0.50; 95%CI, 0.29-0.87; p&lt;0.001). In the first-line setting, overall adverse events rates were higher in the older group (34% vs 20%; p=0.04), including cardiotoxicity (7% vs 0.9%; p=0.02), and on-treatment deaths (5% vs 0%; p=0.01).
ConclusionElderly patients with HER2-positive ABC demonstrated shorter chemotherapy durations, poorer overall survival, and increased rates of adverse events despite having similar disease characteristics and treatment patterns. Prospective studies are required to improve outcomes in the elderly HER2 positive population.
Citation Format: Nicole Evans, Angelyn Anton, Rachel Wong, Sheau Wen Lok, Richard De Boer, Laeeq Malik, Sally Greenberg, Belinda Yeo, Louise Nott, Gary Richardson, Ian M Collins, Javier Torres, Frances Barnett, Peter Gibbs, Bianca Devitt. Real world outcomes in elderly women with HER2 positive advanced breast cancer [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS6-35.