5P - Interpreting Genomic Diversity for Breast Cancer: Molecular Subtypes of Breast Cancer in Very Young Women (≤35 Y) in Western Turkey

Abstract

Background: Approximately one in forty women diagnosed with early breast cancer is very young (<35 years). While some preliminary studies suggest that the distribution of the different biological subtypes of breast cancer is different in young women with a higher prevalence of triple negative and Human Epidermal Growth Factor Receptor 2 (HER-2)+ disease, an accurate molecular subtyping of breast cancer in these patients is lacking. Thus, a clear molecular subtyping of breast cancer in these patients should be investigated. The main aim of this study is to determine the molecular subtypes of very young breast cancer patients in Western Turkey. Methods: We conducted a retrospective analysis of very young women diagnosed with breast cancer from 1999 to 2011 at Ege University Faculty of Medicine (EUFM). Data were collected from patients' medical and pathological reports. Molecular subtyping was done based on the immunohistochemical evaluation of estrogen, progesterone receptors (ER, PR), Ki-67 and HER2/neu which are accepted as surrogate markers for identifying molecular subtypes of breast cancer. SAS was used for statistical analysis. Results: A total number of 3513 medical records of newly diagnosed breast cancer patient were reviewed and 216 (5 %) of them were ≤ 35 years at the time of the diagnosis. The mean age at the diagnosis was 31.6± 3. Luminal B (40.3%) was the most common subtype. Triple negative disease was the second most common type (16%) and Luminal A tumors, accepted as the most favorable subtype, was the least common subtype for this patient population (13.4%). More than 2/3 of the patients (67.4%) had axillary lymph node involvement which points out an unfavorable prognosis. In our study, triple negative subtypes showed the worst prognosis by means of developing early metastasis and decreased survival compared with other molecular subtypes. Conclusion: Very young (≤ 35 years old) breast cancer patients have a different biopathological profile with a predominance of unfavorable prognostic factors, by means of both new molecular subtypes and clinicopathological assessment. When deciding a treatment, not only the young age, but the molecular biology of the tumour should always be taken into account to tailor the treatment, thus molecular subtyping is a research priority in these patients. Disclosure: All authors have declared no conflicts of interest.