Prevalence of Molecular Subtypes of Breast Cancer: A Single Institutional Experience of 2062 Patients

Objective: The aim of the study was to analyze the prevalence of molecular subtypes of all breast cancer patients treated at tertiary cancer centre in West India in 12 years. Materials and Methods: A retrospective observational study carried out in Tertiary Cancer Care Centre in Western India. Electronic medical records of all breast cancer patients were retrieved from the hospital database between March 2007 to March 2019. Patient's characteristic, histological features and molecular subtypes were collected and analyzed. Results: A total of 2062 women fulfilled the criteria for this study and were analyzed. The median age of study population was 51 years (range 22-100 years). Among these, 1357 (65.8%) were of <= 55 years and 705 (34.2%) were over 55 years. The overall incidence of Hormonal Receptor-positive patients (either estrogen-receptor (ER) or progesterone-receptor (PR) or both) was 1162 (56.4%). The Mean tumor size was 3.8cm (range 0-18cm). The most common histology was IDC (96%). Axillary nodes were positive in 62.5%. Luminal type A was positive in 762 (37%) patients while Luminal type B was present in 157 (7.6%) patients. Basal-like subtype was observed in 537 (26%) patients while HER2 rich subtype was seen in 229 (11.1%). The incidence of Luminal A subtype increased with age. The highest observed among patients (72%) aged 70 years or more. Incidence of Basal like subtype was highest in patients less than 30 years (52%). Conclusion: Luminal-like disease is the most common molecular subtype in India. Identification of Basal like breast cancer, a highly aggressive, biologically and clinically distinct subtype different than its non-basal variant, is important for treatment planning and target therapy.