Effect of Tumor Stage and Molecular Subtypes on Five-Year Overall Survival in Breast Cancer: A Single-Center Study From Pakistan.

Background Breast cancer is a biologically diverse malignancy in which stage at diagnosis and receptor-defined molecular subtype are important determinants of prognosis. In Pakistan, delayed presentation remains common, partly because of limited awareness, socioeconomic barriers, and variable access to diagnostic and treatment services. This study evaluated five-year overall survival (OS) by tumor stage and molecular subtype in a curative-intent breast cancer cohort from a tertiary cancer center in Pakistan. Methodology We retrospectively reviewed women diagnosed in 2020 with biopsy-confirmed invasive breast cancer, clinical Stage I-III disease, no distant metastasis (M0), and treatment with curative intent. OS was measured from the date of diagnostic biopsy to death from any cause or last documented follow-up. Survival was estimated using the Kaplan-Meier method, group differences were assessed with log-rank testing, and independent prognostic factors were evaluated using multivariable Cox regression, including stage, molecular subtype, age, and tumor grade. Treatment characteristics, including surgery type, chemotherapy timing, and radiotherapy completion, were summarized descriptively. Results Among 160 women, 54 (33.8%) deaths occurred during a median follow-up of 5.36 years. Treatment characteristics showed that 159 (99.4%) patients underwent surgery, 158 (98.8%) patients received chemotherapy, and 154 (96.3%) patients completed radiotherapy. Overall five-year OS was 66.3% (95% confidence interval (CI) = 58.4-73.0). Five-year OS was significantly higher in Stage I-II disease than in Stage III disease: 86.4% versus 45.6%, respectively (p < 0.001). Human epidermal growth factor receptor 2 (HER2)-enriched tumors, defined as hormone receptor-negative/HER2-positive disease, had the lowest observed five-year OS at 47.8%, compared with 72.3% for hormone receptor-positive disease and 62.8% for triple-negative breast cancer, although the unadjusted log-rank comparison did not reach statistical significance (p = 0.092). In multivariable analysis adjusted for stage, molecular subtype, age per 10-year increase, and tumor grade, Stage III disease (hazard ratio (HR) = 5.22; 95% CI = 2.66-10.26; p < 0.001) and HER2-enriched subtype (HR = 2.14; 95% CI = 1.06-4.32; p = 0.033) were independently associated with higher mortality. Conclusions In this single-center curative-intent cohort, Stage III disease was the strongest predictor of poorer five-year OS. HER2-enriched disease was also associated with worse adjusted survival, although this finding should be interpreted cautiously because HER2-directed therapy exposure and completion were not reliably captured. These results support efforts to improve earlier detection, timely referral, and access to evidence-based systemic therapy, including HER2-targeted treatment where clinically indicated.