Molecular Subtypes and Radiotherapy as Determinants of Survival in Invasive Breast Cancer: Insights from a Single-Center Study.

OBJECTIVES

Invasive breast cancer (IBC) is a heterogeneous disease, with molecular subtypes guiding treatment and prognosis. Radiotherapy, a key component of breast cancer therapy, may vary in efficacy across subtypes. This study assessed the distribution of molecular subtypes and the use of radiotherapy, as well as their associations with clinicopathological features, overall survival (OS), and disease-free survival (DFS) in a single-center cohort.

METHODS

We retrospectively analyzed 178 IBC patients diagnosed between 2018 and 2021. Associations between molecular subtypes (luminal A, luminal B, human epidermal growth factor receptor 2 enriched, triple-negative breast cancer [TNBC]) and clinical features were assessed via χ2 tests. Kaplan-Meier and Cox regression analyses were performed on 158 patients with follow-up, after propensity score matching.

RESULTS

Tumor size (P = 0.012), American Joint Committee on Cancer stage (P = 0.004), histological grade (P < 0.001), and chemotherapy (P = 0.016) differed significantly among the four molecular subtypes. OS and DFS varied by subtype (P = 0.024 and P = 0.042), with TNBC showing poorer outcomes than luminal B (OS P = 0.006, DFS P = 0.007) and luminal A (OS P = 0.035). Radiotherapy was associated with improved OS and DFS (P = 0.04 and P = 0.03). Multivariate Cox analysis confirmed radiotherapy as an independent factor for improved OS (hazard ratio 0.112; 95% confidence interval 0.022-0.566) and DFS (hazard ratio 0.129; 95% confidence interval 0.026-0.632).

CONCLUSIONS

IBC displays molecular subtype-specific differences in tumor behavior and prognosis, with TNBC linked to the worst clinical outcomes. Radiotherapy independently improved OS and DFS across all subtypes, supporting its continued role regardless of molecular profile.