Evaluating the impact of multi-level interventions on immunohistochemistry uptake in breast cancer patients in Nigeria: A retrospective cross-sectional study.

e13639 Background: Breast cancer (BCA) is the most common malignancy globally, with highest mortality in Sub-Saharan Africa (SSA). Immunohistochemistry (IHC) is crucial for prognostic and predictive molecular subtyping. Despite the introduction of IHC infrastructure in Nigeria 25 years ago and multi-level interventions, IHC uptake remains low. Methods: This retrospective cross-sectional study assessed IHC uptake among 1,746 newly diagnosed BCA patients at a large tertiary public hospital in Nigeria (2019-2023). IHC rate was calculated as the proportion of patients with recorded molecular receptor subtype data. Treatment plan and mortality outcome were also documented. Results: Only 35.1% (613/1746) of patients obtained IHC workup prior to treatment. Among patients with IHC results, 63.0% were Triple Negative Breast Cancer (TNBC), 26.8% Hormone Receptor Positive, 4.89% Her2 Positive, and 2.44% Triple Positive. Compared to previous reports (21.6%), there's a 14% absolute increase in IHC uptake over a decade. Conclusions: Despite multi-level interventions, IHC uptake remains suboptimal, contributing to high BCA mortality in SSA compared to high income countries. Culturally adapted, patient-facing interventions are needed to improve IHC uptake and mortality outcomes.