Abstract
BACKGROUND: Breast cancer is often classified into subtypes using immunohistochemical markers. These subtypes have distinct biological behaviour. This study was conducted with the aim of estimating the distribution of various subtypes of breast cancer in Indian population based on immunohistochemistry markers and to determine the clinical features, pathology and outcomes of these subtypes of breast cancer. MATERIALS AND METHODS: A retrospective study was undertaken and all patients of breast cancer over a 5 year period were included. These patients were divided into 4 subgroups depending on the presence or absence of immunohistochemical markers: i) Luminal A (ER/PR+, Her 2 neu-); ii) Luminal B (ER/PR+, Her 2 neu+); iii) Her 2 enriched (ER-/PR-, Her 2 neu+) and; iv) Triple negative (ER-, PR-, Her2 neu-). Clinical and pathological features and survival were compared between patients in the 4 subgroups. RESULTS: Luminal A subgroup had majority of patients (43.8%). Patients in Luminal B, Her 2 enriched, and Triple negative subgroups were 14.8%, 16.1% and 25.3%. Median follow-up of patients was for 34 months. Luminal A subgroup patients were more likely to be postmenopausal and have smaller and lower grade (I/II) tumours with better survival (OS-91.06%). Patients in the Triple negative subgroup were more likely to be premenopausal (p-value 0.036, odds ratio 0.611, CI 0.394-0.949), have larger and higher grade (III) tumours with worse overall survival (OS-88.46%, odds ratio 1.32, 95%CI 0.602-2.39). Her 2 enriched group patients had bad prognostic features like larger size of tumour and higher grade of tumour and worst survival among all the subgroups (OS-85.07%, odds ratio 1.78, 95% CI 0.767-4.163). However, these outcomes were not statistically significant for the subgroups. CONCLUSION: A retrospective study was undertaken of breast cancer patients in India, according to subtypes based on immunohistochemistry. Luminal A had prognostic features and survival which was better as compared to other subgroups (Luminal B, Her 2 enriched and Triple negative). Incidence of patients with Triple negative breast cancer was higher in the premenopausal period. Patients with Her 2 enriched breast cancer had the worst survival among all the subgroups.