Determinants of overall survival in the South African Breast Cancer and HIV Outcomes cohort.

11158 Background: Sub-Saharan Africa (SSA) has very low breast cancer (BC) survival. South Africa, unlike most SSA countries, is an upper middle-income country where patients are less burdened with cancer diagnostic and treatment costs. We aimed to provide five-year overall survival (OS) estimates and determinants among South African women with BC diagnosed and treated within the public health system. Methods: The South African Breast Cancer and HIV Outcomes prospective cohort study enrolled adult women recently diagnosed with invasive BC from four South African academic hospitals. We collected detailed sociodemographic, clinical, treatment, and outcomes data. Women were followed for five years or until December 31, 2023, whichever was earlier, and our primary outcome was five-year OS. Impacts of potential determinants on OS were assessed using individual Cox proportional hazard models focused on nine variable domains ( i.e., treating hospital, social status, BC risk factors, smoking, cardiovascular disease (CVD), HIV status, BC type, BC treatments, and age) and a combined model that also included adjustments for background mortality. Results: Between July 2015 and Feb 2019, we enrolled 2,838 women newly diagnosed with histopathologically confirmed invasive BC, of whom 58% had III or IV disease. At the end of follow-up, 1555 (55%) of the women had died, 1191 (42%) survived for five years, 33 (1%) were censored at study’s end, and 59 (2%) were lost to follow up. The five-year OS was 44.3% (95% CI 42.5-46.2). In the full model, the variables with the largest impact on five-year survival were late-stage at diagnosis (HR 2.4 [95% CI 2.0-2.7] for stage III and HR 5.0 [95% CI 4.1-6.1] for stage IV disease, both compared with stage I/II) and differing degree of treatments received (no treatment received: HR 8.2 [95% CI 5.9-11.3]; chemotherapy and endocrine therapy: HR 1.9 [95% CI 1.4-2.6]; endocrine therapy only: HR 2.2 [95% CI 1.6-3.2]; chemotherapy only: HR 4.8 [95% CI 3.4-6.6]; surgery only: HR 3.0 [95% CI 1.9-4.8]; surgery and chemotherapy: HR 1.8 [95% CI 1.3-2.5], all compared with surgery and endocrine treatments). Other variables significantly associated with survival were treating hospital, relationship status, employment, education, family history of cancer, CVD, and HIV infection. Conclusions: Interventions to improve BC survival in South Africa’s public health system should prioritize earlier diagnosis of cancer and expansion of the infrastructure supporting diagnostic and treatment services. Concurrently, South African BC patients with low socioeconomic status, HIV infection, and/or comorbid CVD are uniquely vulnerable and their barriers to accessing care must be better understood.