Molecular Subtypes of Breast Cancer in Arab Women: Distribution and Prognostic Insights

Understanding the ethnic molecular subtype characteristics of breast cancer (BC) in Saudi women is crucial for providing comprehensive prognostic information and optimizing patient outcomes, making it essential to study their distribution and impact on survival.

This hospital-based cohort study analyzed clinic-pathological data from 1,035 Saudi women diagnosed with invasive BC and followed for 12 years, at King Faisal Specialist Hospital & Research Center. Cancers were classified into four molecular subtypes: luminal A, luminal B, human epidermal growth factor receptor 2 (HER2)-enriched, and triple-negative. Survival outcomes were assessed using Kaplan-Meier survival curves and Cox proportional hazard models.

Luminal A was the most common molecular subtype (41.7%), followed by luminal B (23.4%), triple-negative (19.5%), and HER2-enriched (15.4%). Age at diagnosis, menopause, and tumor grade were significantly associated with subtypes (p < 0.05). Survival outcomes varied significantly (p = 0.0202), with luminal A and B showing the highest 5-year survival rates (~ 83%), triple-negative at 76.4% (hazard ratio: 1.55), and HER2-enriched tumors had the lowest at 69.1%, with a 1.75-fold higher risk of death. Advanced-stage cancers (III and IV) were strongly associated with increased mortality, with hazard ratios of 2.5 and 7.6, respectively, compared to early-stage disease.

Molecular subtypes and stage at diagnosis are key predictors of mortality in Saudi women with BC. The poor outcomes for HER2-enriched and TNBC subtypes highlight the need for timely diagnosis and targeted treatments, emphasizing the importance of personalized care and addressing ethnic variations in BC diagnosis.