Immunohistochemical biomarkers and overall survival in breast cancer: a real-world cohort from Morocco

Abstract Background Breast cancer is the most common malignancy among women worldwide, with marked disparities in survival outcomes across regions (1). In many low- and middle-income countries, immunohistochemistry remains the cornerstone for tumor biological characterization. This study aimed to evaluate overall survival according to routinely assessed immunohistochemical biomarkers and surrogate molecular subtypes in a large real-world cohort from Morocco. Methods This retrospective monocentric cohort study included 623 patients with invasive breast cancer diagnosed in 2014 at a tertiary referral center in Casablanca. Data on age, estrogen receptor (ER), progesterone receptor (PR), HER2 status, Ki-67 proliferation index, molecular subtype, vital status, and date of death were collected. Overall survival was estimated using the Kaplan–Meier method and compared using the log-rank test. Results At five years, vital status was available for 560 patients. Overall survival at five years was 77.5%. Hormone receptor–positive tumors were associated with significantly improved overall survival compared with hormone receptor–negative tumors (p < 0.0001). High Ki-67 (≥ 14%) was associated with poorer survival (p = 0.0038). Overall survival differed significantly according to triple-negative status, with triple-negative tumors exhibiting the worst outcomes. Conclusions Routinely assessed immunohistochemical biomarkers retain strong prognostic value for overall survival in breast cancer. These real-world data provide important population-specific benchmarks and support the continued use of immunohistochemistry for prognostic stratification in resource-constrained settings.