Approximately 10% of women diagnosed with breast cancer each year in Ireland, are found to have triple negative breast cancer. Triple negative breast cancer, as its name suggests, describes a type of breast cancer which lacks three major receptor usually seen in this disease. These are the oestrogen receptor, the progesterone receptor and the HER2 receptor. Because women with triple negative breast cancer do not have these receptors, this limits their treatment options, and they are not suitable for hormonal therapy or HER2 targeted therapies. The only options remaining are surgery and/or chemotherapy. In addition to this, the biology of these tumours is more aggressive, with many women developing metastasis (the spreading of the tumour from the breast to other parts of the body), within the first 2 years after their diagnosis. We aim to examine women diagnosed with triple negative breast cancer in the West of Ireland from 2001 to 2017. We will determine whether the numbers of triple negative subtypes (4 main subtypes within this disease) have changed the past 17 years, and whether changes in treatment practises such as the type of chemotherapy have improved patient outcomes and reduced the development of metastatic spread. In particular giving the changing demographics in the West of Ireland, these are important questions for treatment planning in the future.