ABSTRACT
Introduction: Our study investigates whether an approximation of breast cancer molecular subtypes using the hormone receptors and HER-2 status prognosticates for disease control after breast conservation therapy (BCT) in node-negative Asian breast cancer patients.
Methods and Materials: We retrospectively reviewed 541 women with node-negative breast cancers treated with BCT between 1989 and 2007. Hormone receptors and HER-2 status were obtained from patients’ histological report. All patients received radiotherapy. Thirty-six percent and 68% of women received chemotherapy and hormonal treatment respectively. Results: Median follow-up of patients is 72 months. Five-year local recurrence free survival (LRFS) is 97.2% for the cohort but differs between subtypes: luminal A, 0.8%; luminal B, 1.4%; HER-2, 3.6% and basal-like, 12.7% (P = 0.047). The 5-year distant disease free survival (DDFS) is 96.4% for the cohort but differs between subtypes: luminal A, 98.2%; luminal B, 92.6%; HER-2, 89.5% and basal-like, 91.5% (P = 0.019). The 5-year disease free survival (DFS) is 94.4% for the cohort but differs between subtypes: luminal A, 97.4%; luminal B, 92.7%; HER-2, 86.3% and basal-like, 85.0% (P = 0.007). Univariate analysis with luminal A as baseline revealed an association of the other 3 subtypes with decreased DFS (P = 0.007), Hazard Ratio (HR) of 2.2, 4.4 and 3.3 to Luminal B, HER-2 and basal subtypes, respectively. On multivariate analysis, HER-2 subtype (AHR = 3.3, 95% CI, 1.1 to 9.8, P = 0.036) and basal-like subtype (HR = 3.5, 95% CI, 1.2 to 9.9, P = 0.019) prognosticate adversely for DFS. Conclusion: The combination of hormone receptors and HER-2 status can be used as surrogates for molecular subtypes in Asian breast cancer patients with node-negative disease to prognosticate LRFS, DFS and DDFS.Breast cancer is a major cause of morbidity and mortality in women worldwide. Asian women have a lower incidence of breast cancer historically but over the last 40 years, breast cancer incidence in countries such as China, Korea and Japan has increased. In Singapore, not only is breast cancer the most common cancer in women, it is also the most rapidly increasing one as well, having more than doubled its incidence over the past 25 years.
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