METASTATIC BEHAVIOUR OF SUBTYPES IN LOCALLY ADVANCED CARCINOMA BREAST.

Introduction:-Prognostic factors have been known to predict the incidence of metastasis in carcinomabreast but the study of subtypes classification based on molecular markers may help in providing more personalized and individualized patient care with a more focused treatment andfollow up of patients with high probability of metastasis at different sites. Methods:-Patients with breast cancer (tissue biopsy proven) diagnosed between 2011 and 2013 were included. Subtypes were defined on the basis of molecular markers (ER, PR and Her 2 Neu) in five categories. (Luminal A, Luminal B, Luminal HER2, HER2 enriched and Basal). Distant sites for metastasis were classified as brain, liver, lung, bone, distant nodal, pleural/peritoneal, and others. Association between the site of relapse and subtype was assessed in multivariate models using logistic regression. Results:-Mean age of diagnosis of patients in the study was 50.71 years (SD-11.493) with 41-50 years(31.5%) being the most common age group. Most of the patients in the study were locally advanced at the time of presentation (69.6%).Incidence of metastasis at the time of presentation was (38.7%) with bone being the most common site. Patients were divided on the basis of molecular subtypes with Basal(27.3%) being the most common subtype closely followed by luminal A(25.2%). Highest incidence of metastasis was seen in Basal subtype (33%) followed by Luminal HER (18.4%) and HER2 Enriched (18.1%). On subset analysis, Bone was the most common site of recurrence in Luminal A (61.5%) and Luminal B (58.8%). Basal and Luminal HER subtypes had Brain as the most common site of metastasis while HER2 Enriched had equal metastasis in liver and brain. Conclusion:-Breast cancer subtypes are associated with distinct patterns of metastatic spread with a high probability of metastasis at the time of presentation as well as later in the life time. Hormone negativetumours had more incidence of metastasis than hormone positive tumours. Moreover, hormonal negative tumours were dominated by visceral metastasis than bony metastasis. It is important to understandthe nuances of these subtypes to predict metastatic behavior, for early imaging and adequate individualized treatment and follow up.