Genetic Signature of Breast Cancer Defines Therapeutic Interventions and Indicates Early Drug Resistance

Breast cancer (BC) is the most prevalent cancer in women and ranks first in diagnosed cancers worldwide, thanks to effective screening strategies. However, morbidity and mortality rates remain high among aggressive subtypes, forcing oncologists to adopt the philosophy of precision oncology in clinical practice. Immunohistochemical analysis of the tumour establishes diagnosis and stratifies BC into four types, according to a globally recognised classification. Tumour cells present a wide diversity in morphological, histological and molecular characteristics, indicating the heterogeneous nature of BC that reflects on different proliferation rates, risks of relapse and metastasis. The differentiation in prognosis and response to treatment underscores the vital need for targeted therapy, specific for each tumour's genetic status, that enhances therapeutic effectiveness. The aim of the present article is to designate the potential of using a novel molecular modality as a diagnostic tool that enlightens oncologists during their therapeutic decisions and raises awareness of therapeutic failure. Next-generation sequencing (NGS) detects a wide gamut of biomarkers and gene mutations in biopsy samples, revealing the precise genetic profile and implicating a personalised therapy. Incorporation of molecular testing in the diagnostic algorithm promises amelioration of therapeutic outcomes, prevention of recurrence and reduction of BC-related mortality.