De novo metastatic breast cancer; clinical characteristics and treatment outcomes in a developing country

Abstract Background: Distant metastasis at the time of diagnosis of breast cancer is found in approximately 6% of new cases and much more in developing countries. Due to distinct biologic and molecular characteristics, de novo Metastatic Breast Cancer (dnMBC) is inherently different from recurrent metastatic breast cancer (rMBC). Data on de novo metastatic breast cancer is limited due to the heterogeneity of the disease and the lack of distinction between rMBC and dnMBC in most of the published literature. In this study, we aim to review the survival outcomes of patients diagnosed with dnMBC treated at a tertiary cancer center in a developing country and to identify factors that affect their outcome. Methods: Using hospital-based database, consecutive patients with pathologically proven dnMBC diagnosed between 2013 and 2017 inclusive were identified. Retrospective chart review was performed to collect demographic data, tumor characteristics, types of treatment, and dates of death/last follow-up. Overall survival (OS) was defined as the time from diagnosis to death from any cause or last follow-up. Survival was estimated using the Kaplan-Meier method and compared between subgroups using log-rank tests. Multivariate analysis was performed using cox regression method. Results: 435 patients (3 males) were included in the analysis. Median age (range) at time of diagnosis was 51 (24- 85) years, and 99 (22.8%) were younger than 40 years. Predominant histology was invasive ductal carcinoma (IDC) in 372 (75.2%) patients, followed by invasive lobular carcinoma (ILC) in 37 (8.5%) patients. Poor prognostic features of the primary tumor were present in majority of patients, including: high grade (n=201, 46%), advanced T-stage (T3/T4) (n=205, 47.2%), and lymph node involvement (n=322, 74%). Most of the tumors expressed hormone receptors (81% ER+, 77% PR+). HER-2neu overexpression was reported in 134 (30.9%) patients while only 24 (5.5%) had triple negative (TN) disease. The most common sites of distant metastases were bone (n=307, 70.6%) followed by lung (n=157, 36.1%) and liver (n=139, 32%). The median OS for all patients was 38 months, and 5-year OS was 32.6%. On univariate analysis, factors associated with poor OS were: GIII (5-year OS: 45.8% in GI and II vs 19.1% in GIII), log rank p<0.001), advanced T-stage (5-year OS: 47% for T1/T2 vs 26.5% for T3/T4 tumors, log rank p<0.001), TN status (5-year OS 0 % in TN vs 35% in non-TN, log rank p<0.001), and metastasis to multiple sites (5-year OS: 50% for metastasis to a single site vs 24% for multiple sites (log rank p<0.001). No difference in OS was observed based on HER-2neu overexpression. On multivariate analysis, high tumor grade (Hazard ratio (HR) =1.6, p=0.002), advanced T-stage (HR=1.6, p=0.003) and triple negative status (HR= 2.1, p=0.008) predicted poor OS. Conclusions: The overall survival of patients with dnMBC remains poor. Better understanding of the disease behaviour and factors affecting survival is required for optimal utilization of available regimens and new drugs to hopefully improve patients’ outcomes. Citation Format: Hanan Almasri, Ayah Erjan, Hebah Abudawaba, Khaled Ashouri, Sara Mheid, Anoud Alnsour, Hikmat Abdel-Razeq. De novo metastatic breast cancer; clinical characteristics and treatment outcomes in a developing country [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P4-07-27.