Abstract PO4-16-06: From Real-World Data to Improved Outcomes: Examining the Impact of Trastuzumab Disparities on Pathological Complete Response and Long-Term Survival in HER-2 Positive Breast Cancer Patients within the Brazilian Public Health System
Authors: Antonini Marcelo , Mattar Andre , Pannain Gabriel , Richter Fernanda Grace Bauk , Amorim Andressa , Diogenes Marina , Ferraro Odair , Gebrim Luiz , Lopes Reginaldo Coelho , Real Juliana 
Published: May 2024

Introduction: Equitable access to healthcare is a fundamental principle of public health, aiming to ensure that all individuals have the opportunity to receive effective treatments. However, disparities in access to healthcare still persist in many countries, including Brazil. These disparities can have significant impacts on the health and well-being of patients, particularly in the case of breast cancer treatment. Neoadjuvant chemotherapy (NAC) has been increasingly used for the treatment of breast cancer, encompassing conditions ranging from locally advanced tumors to early-stage triple-negative and HER-2 positive tumors.

Objectives: The aim of this study is to evaluate the impact of disparities in the use of trastuzumab (Herceptin) within the Brazilian public health system on pathological complete response (pCR), overall survival (OS), and disease-free survival (DFS). We aim to investigate whether variations in access to trastuzumab treatment influence the achievement of pCR and impact long-term survival outcomes in breast cancer patients.

Methods: This retrospective, multicenter cohort study included female patients over 18 years of age with a diagnosis of non-metastatic breast cancer undergoing NAC. pCR was defined as the absence of residual invasive or in situ tumor in the breast and axilla. As an exploratory real-world data study, no confirmatory hypothesis was established, thus no corrections for multiple comparisons were necessary. Overall survival (OS) and disease-free survival (DFS) were estimated using the Kaplan-Meier method, calculated at five years. The study was approved by the Research Ethics Committee with registration number CAAE 64633422.4.0000.5463.

Results: Between 2011 and 2020, a total of 1,891 patients were included in the study, of whom 454 (22.9%) were HER-2 positive. The pCR rate was 25.7%. Trastuzumab was accessed by 291 (64.1%) patients (p &lt; 0.001). Among those who received trastuzumab, pCR was observed in 105 (36.1%) patients, compared to 12 (7.6%) in those who did not have access to trastuzumab (p &lt; 0.001). OS in HER-2 positive patients was 90.1% with pCR and 64.5% without pCR (log-rank p &lt; 0.001), while DFS was 89.2% with pCR and 68.2% without pCR (log-rank p = 0.003). Evaluating OS and DFS in patients who received trastuzumab versus those who did not, OS with trastuzumab and pCR was 94.3% and without pCR was 89.5% (log-rank p &lt; 0.001); OS without trastuzumab and pCR was 83.3% and without pCR was 58.2% (log-rank p &lt; 0.001). DFS in patients who received trastuzumab and achieved pCR was 94.5% and without pCR was 90.5% (log-rank p = 0.05), whereas without trastuzumab and pCR was 79.9% and without pCR was 62.1% (log-rank p = 0.001).

Conclusion: These findings underscore the significant impact of disparities in trastuzumab utilization within the Brazilian public health system on pCR rates and long-term survival outcomes in HER-2 positive breast cancer patients. Access to trastuzumab was associated with higher pCR rates and improved overall and disease-free survival rates. Ensuring equitable access to targeted therapies is crucial for improving treatment response and long-term outcomes in breast cancer patients.

Table 1 Clinicopathological characteristics of patients Legend: AJCC, American Joint Committee on Cancer; IDC, invasive ductal carcinoma; ILC, invasive lobular carcinoma; HR hormonal receptor.

Table 2 - NAC schemas and correlation with pCR. AC-T, doxorubicin + cyclophosphamide – taxane; AC-TH, doxorubicin + cyclophosphamide – taxane+herceptin.

Citation Format: Marcelo Antonini, Andre Mattar, Gabriel Pannain, Fernanda Grace Bauk Richter, Andressa Amorim, Marina Diogenes, Odair Ferraro, Luiz Gebrim, Reginaldo Coelho Lopes, Juliana Real. From Real-World Data to Improved Outcomes: Examining the Impact of Trastuzumab Disparities on Pathological Complete Response and Long-Term Survival in HER-2 Positive Breast Cancer Patients within the Brazilian Public Health System [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-16-06.