The association of isolated tumor cells and micrometastases in regional lymph nodes with the clinical outcome of breast cancer is unclear.

Background Triple-negative breast cancers (TNBC) neither express hormone receptors, nor overexpress HER2. They are associated with poor prognosis, as defined by low five-year survival and high recurrence rates after adjuvant therapy. Overall, TNBC share striking similarities with basal-like breast cancers (BBC), so a number of studies considered them being the same. The purpose of this review is to summarise the latest findings on TNBC concerning its relation and delineation to BBC, discuss the developmental pathways involved and address clinical implications for this complex type of breast cancer. Methods The recent literature from PubMed and Medline databases was reviewed. Results Not all TNBC are of the intrinsic BBC subtype (nonbasal (NB)-TNBC), nor are all BBC triple-negative (non-triple-negative (NTN)-BBC). There is increasing evidence that a triple-negative, basal-like breast cancer (TNBBC) subtype develops mainly through a BRCA1-related pathway. Somatic mutations that contribute to NTN-BBC and NB-TNBC development are possibly not related to this pathway, but may occur randomly due to increased genomic instability in these tumours. Several therapeutic options exist for TNBBC, which exhibited promising results in recent clinical trials. Cytotoxic therapies, e.g. combined treatment with anthracyclines or taxanes, achieved good tumour regression rates in the neo-adjuvant setting, but also showed considerable recurrence during the first 5 years after therapy. Targeted therapy options involve PARP1 and EGFR inhibition, although both approaches still need further investigation. Conclusions TNBC and BBC are not the same disease entity. The TNBBC subtype shows the largest homogeneity in terms of tumour development, prognosis and clinical intervention options.

Studies showed that axillary lymph node dissection can be safely omitted in presence of positive sentinel lymph node(s) in breast cancer patients treated with breast conserving therapy. Since the outcome of the sentinel lymph node biopsy has no clinical consequence, the value of the procedure itself is being questioned. The aim of the BOOG 2013–08 trial is to investigate whether the sentinel lymph node biopsy can be safely omitted in clinically node negative breast cancer patients treated with breast conserving therapy. The BOOG 2013–08 is a Dutch prospective non-inferiority randomized multicentre trial. Women with pathologically confirmed clinically node negative T1–2 invasive breast cancer undergoing breast conserving therapy will be randomized for sentinel lymph node biopsy versus no sentinel lymph node biopsy. Endpoints include regional recurrence after 5 (primary endpoint) and 10 years of follow-up, distant-disease free and overall survival, quality of life, morbidity and cost-effectiveness. Previous data indicate a 5-year regional recurrence free survival rate of 99% for the control arm and 96% for the study arm. In combination with a non-inferiority limit of 5% and probability of 0.8, this result in a sample size of 1.644 patients including a lost to follow-up rate of 10%. Primary and secondary endpoints will be reported after 5 and 10 years of follow-up. If the sentinel lymph node biopsy can be safely omitted in clinically node negative breast cancer patients undergoing breast conserving therapy, this study will cost-effectively lead to a decreased axillary morbidity rate and thereby improved quality of life with non-inferior regional control, distant-disease free survival and overall survival. The BOOG 2013–08 study is registered in ClinicalTrials.gov since October 20, 2014, Identifier: NCT02271828. https://clinicaltrials.gov/ct2/show/NCT02271828